Introduction
Breast cancer (BC) is a heterogeneous disease with numerous subtypes that have different treatment responses and clinical outcomes. Human epidermal growth factor receptor 2 (HER-2) is overexpressed in about 15–25% of BC patients, which results in more aggressive tumour biological activity and worse disease outcomes [1]. It is hypothesised that potential crosstalk exists between the insulin-like growth factor 1 (IGF-1) pathway and epidermal growth factor receptor family and it should also be noted that HER-2 overexpression activates the secretion of interleukin 6 (IL-6). In HER-2-positive subtype, increased IGF signalling tends to accelerate the progression of BC and promote resistance to established therapies [2], causing decreased BC-specific survival [3] and increasing overall mortality [4]. As demonstrated by Camirand et al. co-blocking HER-2 and IGF-1 receptor (IGF-1R) inhibits the growth of HER-2-overexpressing BC cells [5]. A previous study showed that HER-2 overexpression activates a transcriptional inflammatory profile, which includes the secretion of IL-6 in many cell types, and it was demonstrated that secreted IL-6 was important for HER-2 mediated oncogenesis and was mediated by autocrine activation of STAT3 in tumour cell populations, which was enhanced by cellular HER-2 expression and in
in vivo contexts [6].
In the mammary gland and other tissues, IGF-1 signalling pathway has been linked to cell proliferation, development, and differentiation [7, 8]. IGF-1 is a single- chain polypeptide encoded by chromosome 12 [9]. The association between IGF1 polymorphisms and clinical outcome has recently been investigated and established in various types of cancers, such as prostate [10, 11], colorectal [12, 13] and breast cancers [11, 14]. This effect is attributed to its pro-survival signalling pathways that potentially promote the proliferation of neoplastic cells [15]. The levels of circulating IGF-1 are highly influenced by genetic factors [16]. Several polymorphic variants including single nucleotide polymorphisms (SNPs) and microsatellites have been associated with both increased IGF-1 levels and BC risk [17–20]. Also, elevated circulating levels of IGF-I may increase BC risk by increasing breast density [21, 22]. Literature data indicate that the SNPs in the IGF-1 gene region including the IGF-1 (rs7136446) were associated with BC risk [19, 20]. Moreover, previous studies have confirmed that an increased IGF-1 levels were associated with a high risk of BC, especially for premenopausal BC and oestrogen receptor-positive BC [11, 14]. On the other hand, some studies carried out on women with premenopausal and postmenopausal BC did not show an association between IGF-I levels or BC risk [23, 24].
Inflammatory processes participate in the initiation, promotion and metastasis of cancer through various mechanisms [25]. An increasing number of studies have shown a correlation between increased levels of certain cytokines and the development and progression of tumours [26]. IL-6 belongs to the cytokine family and is known to regulate immune reactions and inflammation and promote tumour growth by up-regulating angiogenic and anti-apoptotic proteins [27]. The gene encoding for the IL-6 cytokine is located on human chromosomes 7p15.3 [28]. The best characterised SNP IL-6-174G/C (rs1800795) has been shown to cause IL-6 overexpression at least in part by enabling recognition by other transcription factors [29]. Current findings demonstrate the role of IL-6 in BC progression, metastasis, and anti-cancer immunity these findings suggest that the IL-6/JAK/STAT3 signalling pathway is an actionable target with preclinical and clinical studies demonstrating therapeutic potential in both primary and metastatic BC. Notably, inhibiting the IL-6/JAK/STAT3 signalling axis has been investigated through directly targeting IL-6, IL-6R, gp130 receptor, JAKs, or STAT3 [30].
The first aim of this case-control study was to investigate the association between the rs7136446 polymorphism of IGF-1 and 174G/C polymorphism (rs1800795) of IL-6 with BC in the population of western Algeria. Then to study the distribution of the 2 polymorphisms in the 2 BC subtypes; HER-2 positive and HER-2 negative. Lastly, we aimed to investigate the association of IL-6 (rs1800795) polymorphism with clinicopathological characteristics. This study was carried out for the first time among the Algerian population.
Material and methods
Study population
The study included 221 women, divided into case (with BC, n = 109) and control (without BC, n = 112) groups. The patients in our study were all from western Algeria and were recruited from 2 different oncology units . The Establishment Hospital University of Oran and the University Hospital Centre of Oran. All women were diagnosed with histologically confirmed
in situ and invasive BC. Clinicopathological and sociodemographic data were collected in Table I.
DNA isolation
Peripheral blood samples were collected in ethylenediaminetetraacetic acid tubes for each included patient after written informed consent and stored at –20°C until analysis. DNA was isolated from peripheral white blood cells using 2 different kits of extraction: PureLink™ Genomic DNA Mini Kit (Invitrogen) and MagNa Pure LC Total Nucleic Acid Isolation Kit (Roche), following the manufacturer’s instructions. After isolation, DNA concentration was determined using the Qubit 2.0 fluorometer (ThermoFisher Scientific, 2015).
Single nucleotide polymorphism genotyping
The single nucleotide polymorphisms of the IL-6 gene and IGF-1 were selected according to the National Centre for Biotechnology Information SNPs database (https://www.ncbi.nlm.nih.gov/snp/): rs1800795, rs7136446 . Genotyping was performed in the molecular biology unit of the Institut Pasteur Oran, Algeria by Applied Biosystems 7500 real-time polymerase chain reaction (RT-PCR). The reactions were conducted in final volumes of 20 ml per patient, containing: 10 ml TaqMan Genotyping Master Mix; 1 ml of primers (forward and reverse) and 0.5 ml of probes (FAM and VIC) primers and probes of each gene variant are summarised in Table II; 4 ml of deionised DNA/RNA-free water and 3 ml of DNA sample per patient, these volumes were distributed in 96-well reaction plates (MicroAmp Fast Optical 96-Well Reaction Plate). Amplification was performed by using a Fast RT-PCR System 7500 with FAST (software version 2.0.4) incorporated for SNP genotyping (Applied Biosystems), in the following steps:
- pre-PCR, with a duration of 1 min at 50°,
- pre-incubation of the reaction mixture at 95°C during for 10 min,
- thermocycling at 95°C during 15 s for 40 cycles,
- post-PCR, with a duration of 1 min at 60°.
- Fluorescence data were captured during 40 reaction cycles.
Statistical analysis
The chi-square (2) test was used to determine whether the distribution of genotypes was consistent with the Hardy-Weinberg equilibrium. Genotype frequencies were compared between women with BC and women without the disease from a control group using Pearson’s 2 test. The p values were considered statistically significant when p 0.05. The Bonferroni correction threshold for the significance of association at p 0.025 was mentioned considering the number of tests performed. The odds ratio (OR) and 95% confidence interval (CI) were calculated using SPSS software version 22.0.
Results
Clinical and demographic characteristics of the study population
The study included 221 women (109 cases and 112 controls), recruited from both oncology units in Oran to obtain a more representative sample. These patients represented different regions from western Algeria. Mean age and standard deviation was 51.9 ±11.3 years for cases and 44.7 ±14.2 for controls. Out of the 108 patients 45.4% had cancer in the right breast, (48.1%) in left breast and only (6.5%) had bilateral BC. The majority of patients 64% were presented with histological grade II (SBR), followed by grade III (SBR) 35% and only 1% were found to be in grade I (SBR). Invasive ductal carcinoma was broadly identified in (93%), while lobular and others subtypes represented 7% in 107 patients among 109. Clinical TNM (tumour-nodes-metastasis) stage was evaluated as per American Joint Committee on Cancer (AJCC, 8th edition 2017). More than half of the tumours were classified T2–T3 (59%), while T4 and T1 represented (20%) and (15%) respectively. Tx accorded to rare cases of tumours that cannot be evaluated at the initial diagnosis. One hundred and five out of 109 patients were tested for HER-2 status in which it was positive in 22 (21%) and negative in 83 (79%) of the 105 in- dividuals. The expression of oestrogen receptors (ER) was observed in 68% of the 107 from the overall 109 cases, and progesterone receptors (PR) were observed in 62% of the 106 among 109 cases. 90 patients out of 109 were tested for the expression of Ki-67 and 97% of them were positive. Clinical and demographic characteristics of the study population are summarised in Table I.
Genotyping of IGF-1 (rs rs7136446 T > C) polymorphism
Two hundred and five out of the 221 women (cases n = 109 and controls n = 96) were genotyped for the IGF-1 (rs7136446 T > C). Genotype frequencies of the IGF-1 rs7136446 conformed to the Hardy-Weinberg equilibrium (x2 = 3.31, p = 0.069). The CC genotype was found in 15 (14%) cases and in 37 controls (38.5%), while TT genotype was encountered in 53 (49%) cases and in 21 (22%) controls. As for the genotype CT, it was found in 41 (37%) cases and in 38 controls (39.5%) (Fig. 1A). There was difference in genotype distribution among controls and BC patients (p = 0.00001). The distribution of IGF1 polymorphism is summarised in Table III. Analysis of the distribution of the allelic frequencies of 96 healthy subjects originating from the west of Algeria revealed that the allele (T) represents the minor allele with a frequency of 0.42 (Table III). In addition to that, the analysis of genotype frequencies of the IGF1 rs7136446 polymorphism between the case and control groups showed a statistically significant difference for the minor (TT) genotype as well as the cumulative CT+CC and CT+GG genotypes (respectively 49% vs. 22%, p = 10–4, 86% vs. 61%, p = 0.00004 and 51% vs. 78%, p = 0.00007) also, the analysis of the distribution of the allelic frequency of the allele T revealed a significant difference between the cases and the controls (67% vs. 42%, p = 10–6, OR = 2.88 [1.92–4.30]) (Table III). Furthermore, we studied the correlation between genotypes and the 2 HER-2 positive and HER-2 negative of all 109 cases. A statistical difference was found between the genotype distribution of IGF-1 polymorphism and BC susceptibility after stratification according to HER-2 positive and HER-2 negative status (p = 0.04) but this association did not last after the correction of Bonferroni (Table IV). Indeed, we found the frequency of the cumulative CT+CC genotype was statistically significant (27% vs. 54%, p = 0.02, OR = 3.0 [1.09–8.18]) this association was confirmed after the correction of Bonferroni (Table IV).
Genotyping of IL-6-174 (rs1800795 G > C) polymorphism
All 221 women were genotyped for the IL-6-174 (rs1800795 G > C) polymorphism. Genotype frequencies of the IL-6-174 polymorphism conformed to the Hardy-Weinberg equilibrium (x2 = 1.93; p = 0.165). The CC genotype was found in 2 (5.9%) cases and 0 controls, while the GG genotype was encountered in 83 (11.5%) cases and 82 (7.2%) controls. As for the CG genotype, it was found in 25 cases and 26 controls (Fig. 1B). There was no difference in genotype distribution among controls and BC patients (p = 0.10). The distribution of IL-6 polymorphism is summarised in Table II. Analysis of the distribution of the allelic frequencies of 112 healthy subjects originating from the west of Algeria revealed that the allele (C) represents the minor allele with a frequency of 0.12. Also, the analysis of genotype frequencies of the IL-6 rs1800795 polymorphism between the case and control groups showed no statistically significant difference for the minor (CC) genotype as well as the 2 cumulative genotypes CG+CC and GG+CG (p > 0.05) (Table III). Furthermore, we studied the correlation between genotypes and clinicopathological characteristics including the HER-2 positive and HER-2 negative status in the case group. No statistical difference was found between the genotype distribution of IL-6 polymorphism and BC susceptibility after stratification according to clinicopathological parameters (Table IV) or to HER-2 positive and HER-2 negative (Tables IV, V).
Discussion
In the present case-control study of 221 women, we investigated the association between the IGF1 polymorphism (rs7136446) and BC, and the association between the 174G/C polymorphism (rs1800795) of IL-6 and BC, in the western Algerian population. Then, we compared the distribution of IGF-1 and IL-6 polymorphisms in the 2 HER-2positive and HER-2 negative subgroups among BC patients. Lastly, we focused on studying the association between IL-6 (rs1800695) polymorphism and clinicopathological characteristics with BC.
First, the distribution of allelic frequencies revealed that the T allele is the minor allele with a frequency of 0.42. No study before has shown a similar result. Second, the analysis of the distribution of IGF-1 polymorphism showed a significant association in genotype distribution among controls and BC patients (p = 0.00001). Which indicates that the polymorphism IGF-1 (rs7136446 T > C) does seem to have an effect on the occurrence of BC in the population of western Algeria. This result needs to be confirmed on a larger sample. In another study, IGF-1 (rs7136446) was found to be associated with postmenopausal BCs [31]. However, Costa-Silva et al., did not find a significant association with BC in premenopausal or postmenopausal women [23]. The same result was found by Henningson et al., in a Swedish study, in which they revealed a negative association between a set of 9 haplotypes taggins single nucleotide polymorphism (htSNPs) in 3 haplotype blocks including rs7136446 with IGF-1 levels in this study [32]. In the same context of studying the association between IGF-1 genomic variants with BC, Al-Zahrani et al., demonstrated that other polymorphisms of the IGF-1 gene have been associated with BC risk and increased IGF-1 plasma level [19]. IGF-1 variant (rs7136446) was positively associated with both subgroups of HER-2 (positive and negative) (p = 0.04), but this result did not last after the correction of Bonferroni. To our knowledge, no study has addressed the association between the IGF-1 (rs7136446) and the 2 groups of HER-2 (positive and negative) with BC before. On the other hand, other genomic variants of the IGF-1 gene have been associated with clinical outcome of HER-2 positive BC patients [33, 34].
In order to shape the tumour microenvironment and encourage metastasis, cancer cells primarily communicate with the host via cytokines, which also aid in tumour dissemination, epithelial-mesenchymal transitions (EMT), motility, and invasion [35]. A pro- inflammatory cytokine IL-6 is secreted by a variety of cells in the tumour microenvironment, including malignant cells [36]. IL-6 local and systemic overexpression has been linked to numerous cancer types, including BC [37]. While upregulation of IL-6 serum levels is generally associated with poor prognosis and low survival rate in patients with BC, downregulation of IL-6 is related to a better response to treatment [38, 39]. IL-6 polymorphisms have also been linked to a higher risk of BC. Several studies have been performed on the IL-6 promoter SNP-174 G > C (rs1800795) collected in meta-analysis [40].
The distribution of allelic frequencies revealed that the C allele is the minor allele with a frequency of 0.12. The frequency observed in our population is similar to those reported in the Tunisian population [41]. Second, the analysis of the distribution of IL-6 polymorphism showed no association in genotype distribution among controls and BC patients (p = 0.10). Which indicates that the polymorphism IL-6-174 (rs1800795 G > C) does not seem to have an effect on the occurrence of BC in the population of western Algeria. This result needs to be confirmed on a larger sample. Similar results were found in previous studies [41, 42]. Also, a study on a French Caucasian population showed no association with BC diagnosis or prognosis [43]. A meta-analysis conducted on 25,703 subjects suggested that this polymorphism was not associated with BC risk [40]. In contrast with our study DeMichele et al. [44] found that IL-6-174G/C polymorphism is associated with clinical outcome in a cohort of node-positive BC patients who received high-dose adjuvant therapy [44]. Similarly, a study conducted by Iacopetta et al. on Australian BC subjects concluded that IL6 174C allele was associated with a more aggressive BC phenotype [45]. Pooja et al. were the first to report the protective effect of this polymorphism in BC risk [46].
No significant association was found between IL-6 (rs1800795) and any clinicopathological characteristics like age, grade, and metastases (respectively, p = 0.15, p = 0.85, and p = 0.28). Our results were in agreement with previous genetic studies [41]. In contrast to our findings, it was shown in a previous study that the CC genotypes and C allele of IL-6-174 G > C were higher among BC patients, and they were found to be significantly associated with advanced stage (metastasis) [46]. In another study allelic variations analysis indicated that the risk of developing metastases was higher in patients with the GG genotype at rs1800795 [47]. Metastatic cancer cells undergo 2 phenotype switching processes: mesenchymal-to- epithelial transition and EMT [48]. Inflammation is a well-known factor in the development of EMT [48, 49]. As a result, it has been shown that IL-6 takes part in EMT and increases the recruitment of mesenchymal stem cells to human BC cells [50, 51].
According to some research, the mutant GG genotype is a poor prognostic indicator linked to decreased disease-free survival in ER+ patients following chemotherapy [52] as well as a higher risk of metastasis regardless of ER status [53]. The CC genotype, on the other hand, was connected to a more aggressive behaviour and worse overall survival, according to another study [47]. The responsiveness of BC cells to IL-6 depends heavily on the expression of ER and PR. Hormone-sensitive cells exhibit a higher response to IL-6 than hormone insensitive cells, which is associated with the intrinsic generation of higher IL-6 in these cells [54, 55]. While the ER-expressing BC cells mostly secrete sIL-6R, ER – cells mainly express mIL-6R [56]. It has also been shown that IL-6 suppresses ER – cells under normal condition in an autocrine manner [57]. In our study, no significant association was found between IL-6 (rs1800975) and the expression of ER and PR (respectively p = 0.52 and p = 0.5). In contrast to our result a significant association between the IL-6 (-174) and both the ER and PR+ was revealed [58].
IL-6 variant (rs1800975) was negatively associated with both groups of HER-2 (positive and negative) (p = 0.5). This result was in accordance with another recent Tunisian study, which demonstrated that the distribution of genotype frequencies rs1800795 had no statistical difference between HER-2 positive and HER-2 negative BC [41]. Korobeinikova et al. found an association between the IL-6 (rs1800795) and HER-2 negative status [58]. HER-2 overexpression in BC stem cells has been shown to increase IL-6 production [6]. Furthermore, the activation of the IL-6 inflammatory loop induces trastuzumab-resistance in HER-2 positive BC cells indicating that IL-6’s pro-inflammatory role mediates BC therapeutic resistance [59]. No significant difference was found between the IL-6 variant and the 2 clinicopathological characteristics, the expression of Ki-67, and the location (left or right) of BC (respectively, p = 0.98 and p = 0.4). No study so far has investigated the association between either rs1800795 and Ki-67 expression or between rs1800795 and BC location.
This study is the first report of IGF-1 rs7136446 and rs1800795 polymorphisms in IL-6 gene among BC patients from Algeria. However, several limitations to this study should be noted. First, the samples were obtained from a population of women in Algeria, and thus the findings cannot be generalised. Second, a limited number of SNPs in IGF-1 and IL-6 genes were chosen for this study. We recommend more SNPs that were not well studied previously be included in further studies. Lastly, the results in this study should be confirmed in more regions in Algeria, not only in the west, and in a larger population.
Conclusions
The results of the current study indicate that BC risks are significantly associated with IGF-1 rs7136446 and that IL-6 rs1800795 polymorphism are not associated with BC in the western Algerian population.
Disclosures
- Institutional review board statement: Not applicable.
- We want to thank all the medical staff and medical assistants for their help in collecting biological samples and reviewing medical data.
- Financial support and sponsorship: None.
- Conflicts of interest: None.
References:
1. Loibl S, Gianni L. HER2-positive breast cancer. Lancet 2017; 389: 2415-2429.
2.
Denduluri SK, Idowu O, Wang Z, et al. Insulin-like growth factor (IGF) signalling in tumourigenesis and the development of cancer drug resistance. Genes Dis 2015; 2: 13-25.
3.
Yerushalmi R, Gelmon KA, Leung S, et al. Insulin-like growth factor receptor (IGF-1R) in breast cancer subtypes. Breast Cancer Res Treat 2012; 132: 131-142.
4.
Duggan C, Wang CY, Neuhouser ML, et al. Associations of insulin-like growth factor and insulin-like growth factor binding protein-3 with mortality in women with breast cancer. Int J Cancer 2013; 132: 1191-1200.
5.
Camirand A, Lu Y, Pollak M. Co-targeting HER2/ErbB2 and insulin-like growth factor-1 receptors causes synergistic inhibition of growth in HER2-overexpressing breast cancer cells. Med Sci Monit 2002; 8: Br521-526.
6.
Hartman ZC, Yang XY, Glass O, et al. HER2 overexpression elicits a proinflammatory IL-6 autocrine signalling loop that is critical for tumourigenesis. Cancer Res 2011; 71: 4380-4391.
7.
Christopoulos PFP, Msaouel P, Koutsilieris M. The role of the insulin-like growth factor-1 system in breast cancer. Mol Cancer 2015; 14: 43.
8.
Sachdev D, Yee D. The IGF system and breast cancer. Endocr Relat Cancer 2001; 8: 197-209.
9.
Höppener JW, de Pagter-Holthuizen P, Geurts van Kessel AH, et al. The human gene encoding insulin-like growth factor I is located on chromosome 12 Hum. Genet 1985; 69: 157-160.
10.
Chan JM, Stampfer MJ, Giovannucci E, et al. Plasma insulin- like growth factor-I and prostate cancer risk: a prospective study. Science 1998; 279: 563-566.
11.
Renehan AG, Zwahlen M, Minder C, O’Dwyer ST, Shalet SM, Egger M. Insulin- like growth factor (IGF)-I, IGF binding protein-3, and cancer risk: systematic review and meta-regression analysis. Lancet 2004; 363: 1346-1353.
12.
Rinaldi S, Cleveland R, Norat T, et al. Serum levels of IGF-I, IGFBP-3 and colorectal cancer risk: results from the EPIC cohort, plus a meta-analysis of prospective studies. Int J Cancer 2010; 126: 1702-715.
13.
Ma J, Pollak M, Giovannucci E, et al. A prospective study of plasma levels of insulin-like growth factor I (IGF-I) and IGF-binding protein-3, and colorectal cancer risk among men. Growth Horm IGF Res 2000; 10: S28-29.
14.
Key TJ, Appleby PN, Reeves GK, Roddam AW. Insulin-like growth factor 1 (IGF1), IGF binding protein 3 (IGFBP3), and breast cancer risk: pooled individual data analysis of 17 prospective studies. Lancet Oncol 2010; 11: 530-542.
15.
Kurmasheva RT, Houghton PJ. IGF-I mediated survival pathways in normal and malignant cells. Biochim Biophys Acta2 006; 1766: 1-22.
16.
Harrela M, Koistinen H, Kaprio J, et al. Genetic and environmental components of interindividual variation in circulating levels of IGF-I, IGF-II, IGFBP-1, and IGFBP-3. J Clin Invest 1996; 98: 2612-2615.
17.
Jernström H, Sandberg T, Bågeman E, et al. Insulin-like growth factor-1 (IGF1) genotype predicts breast volume after pregnancy and hormonal contraception and is associated with circulating IGF-1 levels: implications for risk of early-onset breast cancer in young women from hereditary breast cancer families. Br J Cancer 2005; 92: 857-866.
18.
Palles C, Johnson N, Coupland B, et al. Identification of genetic variants that influence circulating IGF1 levels: a targeted search strategy. Hum Mol Genet 2008; 17: 1457-1464.
19.
Al-Zahrani A, Sandhu MS, Luben RN, et al. IGF1 and IGFBP3 tagging polymorphisms are associated with circulating levels of IGF1, IGFBP3 and risk of breast cancer. Hum Mol Genet 2006; 15: 1-10.
20.
Verheus M, McKay JD, Kaaks R, et al. Common genetic variation in the IGF-1 gene, serum IGF-I levels and breast density. Breast Cancer Res Treat 2008; 112: 109-122.
21.
Byrne C, Colditz GA, Willett WC, Speizer FE, Pollak M, Hankinson SE. Plasma insulin-like growth factor (IGF) I, IGF-binding protein 3, and mammographic density. Cancer Res 2000; 60: 3744-3748.
22.
Boyd NF, Stone J, Martin LJ, et al. The association of breast mitogens with mammographic densities. Br J Cancer 2002; 87: 876-882.
23.
Costa-Silva DR, da Conceição Barros-Oliveira M, Borges RS, et al. Insulin-like growth factor 1 gene polymorphism in women with breast cancer. Med Oncol 2017; 34: 59.
24.
Henningson M, Hietala M, Törngren T, Olsson H, Jernström H. IGF1 htSNPs in relation to IGF-1 levels in young women from high-risk breast cancer families: implications for early- onset breast cancer. Fam Cancer 2011; 10: 173-185.
25.
Greten FR, Grivennikov SI. Inflammation and cancer: triggers, mechanisms, and consequences. Immunity 2019; 51: 27-41.
26.
Zamarron BF, Chen W. Dual roles of immune cells and their factors in cancer development and progression. Int J Biol Sci 2011; 7: 651-658.
27.
Rašková M, Lacina L, Kejík Z, et al. The role of IL-6 in cancer cell invasiveness and metastasis-overview and therapeutic opportunities. Cells 2022; 11: 3698.
28.
Terry CF, Loukaci V, Green FR. Cooperative influence of gene-tic polymorphisms on interleukin 6 transcriptional regulation. J Biol Chem 2000; 275: 18138-18144.
29.
Saha A, Bairwa NK, Ranjan A, Gupta V, Bamezai R. Two novel somatic mutations in the human interleukin 6 promoter region in a patient with sporadic breast cancer. Eur J Immunogenet 2003; 30: 397-400.
30.
Dethlefsen C, Hojfeldt G, Hojman P. The role of intratumoural and systemic IL-6 in breast cancer Breast. Cancer Res Treat 2013; 138: 657-664.
31.
Shi J, Aronson KJ, Grundy A, et al. Polymorphisms of insulin-like growth Factor 1 pathway genes and breast cancer risk. Front 2016; 6: 136.
32.
Henningson M, Hietala M, Torngren T, Olsson H, Jernstrom H. IGF1 htSNPs in relation to IGF-1 levels in young women from high-risk breast cancer families: implications for early-onset breast cancer. Fam Cancer 2011; 10: 173-185.
33.
Muendlein A, Lang AH, Geller-Rhomberg S, et al. Association of a common genetic variant of the IGF-1 gene with event-free survival in patients with HER2-positive breast cancer. J Cancer Res Clin Oncol 2013; 139: 491-498.
34.
Winder T, Zhang W, Yang D, et al. Germline polymorphisms in genes involved in the IGF1 pathway predict efficacy of cetuximab in wild-type KRAS mCRC patients. Clin Cancer Res 2010; 16: 5591-5602.
35.
Yamaguchi H, Condeelis J. Regulation of the actin cytoskeleton in cancer cell migration and invasion. Biochim Biophys Acta 2007; 1773: 642-652.
36.
Bromberg J, Wang TC. Inflammation and cancer: IL-6 and STAT3 complete the link. Cancer Cell 2009; 15: 79-80.
37.
Kozlowski L, Zakrzewska I, Tokajuk P, Wojtukiewicz MZ. Concentration of interleukin-6 (IL-6), interleukin-8 (IL-8) and interleukin-10 (IL-10) in blood serum of breast cancer patients Rocz Akad Med Bialymst 2003; 48: 82-84.
38.
Shibayama O, Yoshiuchi K, Inagaki M, et al. Association between adjuvant regional radiotherapy and cognitive function in breast cancer patients treated with conservation therapy. Cancer Med 2014; 3: 702-709.
39.
Guo Y, Xu F, Lu T, Duan Z, Zhang Z. Interleukin-6 signalling pathway in targeted therapy for cancer. Cancer Treat Rev 2012; 38: 904-910.
40.
Yu KD, Di GH, Fan L, Chen AX, Yang C, Shao ZM. Lack of an association between a functional polymorphism in the interleukin-6 gene promoter and breast cancer risk: a meta-analysis involving 25,703 subjects. Breast Cancer Res Treat 2010; 122: 483-488.
41.
Bouhniz OE, Zaied S, Naija L, et al. Association between HER2 and IL-6 genes polymorphisms and clinicopathological characteristics of breast cancer: significant role of genetic variability in specific breast cancer subtype. Clin Exp Med 2020; 20: 427-436.
42.
Balasubramanian SP, Azmy IA, Higham SE, et al. Interleukin gene polymorphisms and breast cancer: a case control study and systematic literature review. BMC Cancer 2006; 6 : 188.
43.
Chérel M, Campion L, Bézieau S, et al. Molecular screening of interleukin-6 gene promoter and influence of 174G/C polymorphism on breast cancer. Cytokine 2009; 47: 214-223.
44.
DeMichele A, Martin AM, Mick R, et al. Interleukin-6-174G > C polymorphism is associated with improved outcome in high-risk breast cancer. Cancer Res 2003; 63: 8051-8056.
45.
Iacopetta B, Grieu F, Joseph D. The –174 G/C gene polymorphism in interleukin-6 is associated with an aggressive breast cancer phenotype. Br J Cancer 2004; 90: 419-422.
46.
Pooja S, Chaudhary P, Nayak LV, et al. Polymorphic variations in IL-1, IL-6 and IL-10 genes, their circulating serum levels and breast cancer risk in Indian women. Cytokine 2012; 60: 122-128.
47.
Padala C, Puranam K, Shyamala N, et al. Genotypic and haplotype analysis of Interleukin-6 and -18 gene polymorphisms in association with clinicopathological factors in breast cancer. Cytokine 2022; 160: 156024.
48.
Lamouille S, Xu J, Derynck R. Molecular mechanisms of epithelial-mesenchymal transition Nat Rev Mol Cell Biol 2014; 15: 178-196.
49.
Ricciardi M, Zanotto M, Malpeli G, et al. Epithelial-to-mesenchymal transition (EMT) induced by inflammatory priming elicits mesenchymal stromal cell-like immune modulatory properties in cancer cells. Br J Cancer 2015; 112: 1067- 1075.
50.
Madden KS, Szpunar MJ, Brown EB. Beta-adrenergic receptors (beta-AR) regulate VEGF and IL-6 production by divergent pathways in high beta-AR-expressing breast cancer cell lines. Breast Cancer Res Treat 2011; 130: 747-758.
51.
Korkaya H, Kim GI, Davis A, et al. Activation of an IL6 inflammatory loop mediates trastuzumab resistance in HER2+ breast cancer by expanding the cancer stem cell population Mol Cell 2012; 47: 570-584.
52.
DeMichele A, Gray R, Horn M, et al. Host genetic variants in the interleukin-6 promoter predict poor outcome in patients with oestrogen receptor-positive, node-positive breast cancer. Cancer Res 2009; 69: 4184-4191.
53.
Abana CO, Bingham BS, Cho JH, et al. IL-6 variant is associated with metastasis in breast cancer patients. PLoS One 2017; 12: e0181725.
54.
Chavey C, Bibeau F, Gourgou-Bourgade S, et al. Oestrogen receptor negative breast cancers exhibit high cytokine content. Breast Cancer Res 2007; 9: R15.
55.
Fontanini G, Campani D, Roncella M, et al. Expression of interleukin 6 (IL-6) correlates with oestrogen receptor in human breast carcinoma. Br J Cancer 1999; 80: 579-584.
56.
Chiu JJ, Sgagias MK, Cowan KH. Interleukin 6 acts as a paracrine growth factor in human mammary carcinoma cell lines. Clin Cancer Res1996; 2: 215-221.
57.
Selander KS, Li Li, Watson L, et al. Inhibition of gp130 signalling in breast cancer blocks constitutive activation of Stat3 and inhibits in vivo malignancy. Cancer Res 2004; 64: 6924-6933.
58.
Korobeinikova E, Ugenskiene R, Insodaite R, et al. Association of angiogenesis and inflammation-related gene functional polymorphisms with early-stage breast cancer prognosis. Oncol Lett 2020; 19: 3687-3700.
59.
Korkaya H, Kim GI, Davis A, et al. Activation of an IL6 inflammatory loop mediates trastuzumab resistance in HER2+ breast cancer by expanding the cancer stem cell population. Mol Cell 2012; 47: 570-584.
