Breast cancer is the most common cancer in women worldwide, affecting 1 in 8 women by the age of 85 [1, 2]. It is also the second leading cause of cancer-related death in women, with a mortality rate of 1 in 37 [1, 2]. Despite significant improvements in early detection and treatment, which have greatly enhanced survival rates, 30% of patients with early-stage breast cancer still experience recurrence [3]. Breast cancer is a heterogeneous disease with various molecular subtypes, often classified into clinical subtypes based on hormone receptor status [4]. Luminal A and B subtypes are particularly relevant for this study due to their distinct prognoses [5, 6]. Luminal A breast cancer is characterized by lower expression of the estrogen receptor (ER) and progesterone receptor (PR), a high histological grade, and better overall and disease-free survival [7, 8]. In contrast, luminal B breast cancer, which accounts for nearly 40% of all breast cancer cases, is associated with aggressive clinical behavior and high expression of ER and PR [9, 10].

Breast cancer progression involves various mechanisms, including the interferon-gamma gene (IFNG) expression. Interferon-gamma is a cytokine crucial for host defense against many pathogens and has been reported to induce many immunosuppressive markers such as programmed death-ligand 1 (PD-L1), programmed death-ligand 2 (PD-L2), cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), and indoleamine-2,3-dioxygenase (IDO), leading to tumor cells escaping hosts’ immune systems [4, 11, 12, 13, 14, 15]. Serum interferon-gamma has been reported to correlate with disease outcomes in hormonally dependent breast cancers [16]. Studies have reported that single nucleotide polymorphisms (SNPs) in the IFNG gene can influence the risk of breast cancer[17, 18, 19]. The T allele in the IFNG +874 (T$>$A) gene polymorphism (rs2430561) has been associated with a lower risk of breast cancer in the Iranian population [17], but it increased the risk of breast cancer in the Turkish population [18]. Similarly, the -56C/T gene polymorphism (rs2234711) in interferon-gamma receptor 1 (IFNGR1) correlates with an augmented risk of early gastric carcinoma [19]. Although polymorphisms in the IFNG gene have been associated with a high risk of breast cancer, to our knowledge, limited studies have reported IFNG polymorphisms in relation to primary breast cancer subtypes. Hence, this study evaluated the allele and genotype frequencies of the IFNG SNPs in relation to primary breast cancer subtypes, luminal A and luminal B.

In this study, we present novel findings that IFNG polymorphisms rs1861493 and rs1861494 are linked to an increased risk of breast cancer, with the A allele of rs1861493 and the T allele of rs1861494 identified as the risk alleles. We also report that the IFNG polymorphism rs2430561 is associated with breast cancer risk, with the A allele serving as the risk allele. Our analysis revealed that the allele frequencies of these three polymorphisms differ between two common breast cancer subtypes: Luminal A and luminal B. Specifically, the risk alleles for rs1861493, rs1861494, and rs2430561 were found to be more prevalent in the luminal B subtype, which is known for its more aggressive nature compared to the luminal A subtype. Furthermore, we observed that the rs2430561 AA genotype is associated with increased breast cancer severity. This genotype was particularly linked to more severe breast cancer cases within the luminal B subtype. Significant differences in allele frequencies and genotypic associations between luminal A and B were noted when applying various genetic models. These differences were most pronounced under the recessive model for all three IFNG polymorphisms and the homozygote model specifically for rs2430561. These findings demonstrate the potential role of IFNG polymorphisms in influencing both the risk and severity of breast cancer, especially in relation to the aggressiveness of the disease.

IFNG polymorphisms play an essential role in several processes involved in cancer progression. However, few studies have examined SNPs in the IFNG gene in relation to cancer. The IFNG +874 T$>$A polymorphism (rs2430561) has been associated with decreased [17] or increased risk of breast cancer in the Turkish population [18]. The discrepancy between the two studies could be related to the different ethnic backgrounds of the two study populations, as it has been reported that the IFNG allele frequencies of the +874 T$>$A polymorphism are quite variable in various populations [23]. The other possible explanation is the different allele frequencies in the control group of the two studies. The IFNG +874 T$>$A polymorphism allele frequencies are similar for the cancer patients in the two studies, with an A/T percentage of 49.8%/50.2%, respectively, in the study by Kamali-Sarvestani et al. [17] and 52.5%/47.5%, respectively, in the study by Karakus et al. [18]. However, there are distinct allele frequencies for the two control groups, with an A/T percentage of 56.7%/43.3%, respectively, in the Kamali-Sarvestani et al.’s study [17] and 44.8%/55.2%, respectively, in the Karakus et al. study [18]. It is worth noting that our current study reported similar allele frequencies for the IFNG +874 T$>$A polymorphism with the study by Karakus et al. [18] in both the control group (A/T percentage as 44.94%/55.06%) and cancer patients (A/T as 52.99%/47.01%). Notably, a 2011 study reported that the rs2430561 polymorphism is associated with both the risk and prognosis of breast cancer, identifying the T allele as the risk allele [24]. This finding is particularly intriguing because the prevalence of the T allele observed in that study was notably low: 33.68% in the control group and 50.31% in breast cancer patients. These figures are considerably lower than the allele frequencies reported in Asian populations, where the T allele is often more prevalent (https://www.ncbi.nlm.nih.gov/snp/rs2430561#frequency_tab). This discrepancy suggests that genetic variations and their associations with breast cancer risk might differ significantly across populations. Moreover, such differences could be due to population-specific genetic backgrounds, environmental factors, or methodological variations in allele frequency assessments. This highlights the importance of contextualizing genetic findings within specific population groups and underscores the need for further research to understand how genetic risk factors, such as rs2430561, contribute to breast cancer across diverse populations.

Furthermore, genetic variation in the IFN signaling pathway has been implicated in the risk and survival outcomes for colon and rectal cancers [24]. However, the specific polymorphisms IFNG 874 T$>$A (rs2430561) in non-polyposis colon cancer and IFNG 5644 in a Korean cohort did not demonstrate a significant association with colon and rectal cancer risk [25, 26]. This contrasts with findings in breast cancer research, where the roles of rs1861493 and rs1861494 remain less explored. Notably, a recent study from 2022 reported that rs1861493 is associated with an increased risk of breast cancer, suggesting a potential role in susceptibility to this disease [27]. Meanwhile, rs1861494 has been identified as a predictor of cytogenetic and molecular response to imatinib therapy in chronic myeloid leukemia [28]. In addition, evidence from a study on colorectal cancer patients indicated that the AA (TT) genotype of rs1861494 is linked to a higher risk of cancer recurrence [29]. This finding partially supports our results, which show that the rs1861494 TT genotype is more prevalent in the luminal B subtype and is associated with a poorer prognosis. Collectively, these findings highlight that while some IFNG polymorphisms may not consistently predict cancer risk across different types, rs1861493 and rs1861494 show notable associations with breast cancer risk and severity. This highlights the importance of further research into these polymorphisms to fully understand their role in cancer pathology and prognosis and how they might differ across various cancer types and populations.

Several limitations need to be addressed to understand these implications of the study fully. Firstly, the control group data from the European ALFA study might not accurately reflect the genetic makeup of the Greek population, potentially leading to inaccurate interpretations of allele frequency differences and affecting the study’s conclusions. Additionally, including both males and females in the control populations, while the study patients are exclusively female, introduces a gender-related bias that could skew allele frequency comparisons. The study also faces limitations due to the exclusion of triple-negative and HER2-positive breast cancer subtypes owing to their small sample sizes. This exclusion weakens the analysis and could introduce bias, as it limits the study’s scope and may not fully capture the role of IFNG polymorphisms across all breast cancer subtypes.

Overall, these study’s findings suggest that IFNG polymorphisms may have distinct functional roles in different cancers, with notable associations identified between these genetic variations and breast cancer subtypes. Despite the limitations as addressed above, the identified associations between IFNG polymorphisms and breast cancer risk and severity, particularly in relation to the more aggressive luminal B subtype, highlight their potential significance in breast cancer susceptibility. These findings suggest that IFNG polymorphisms could influence both the risk of developing breast cancer and its clinical progression. Further research is needed to confirm these associations, explore their relevance across different subtypes, and address the noted limitations.

During the preparation of this work, the authors used ChatGPT to check spelling and grammar of the Introduction, Discussion, and Conclusion. After using this tool, the authors reviewed and edited the content as needed and took full responsibility for the content of the publication.

Data is available upon reasonable request from the first named author.

All authors confirm that the publication follows the ICMJE recommendations. Conceptualization, VA, SF, NK, and KN; methodology, NK, VA, SF, and KN; collection of samples, SV, JK, and AT.; validation, SF, XY, and NK; formal analysis, SF, XY, and NK; resources, VA; data curation, NK, SF, XY, SV, IF, AT, KN, and VA; writing—original draft preparation, NK, and XY; writing—review and editing, NK, JK, SF, XY, SV, IF, AT, KN, and VA; supervision VA, KN, and SF; project administration, VA; funding acquisition, VA. All authors have read and agreed to the published version of the manuscript. All authors have participated sufficiently in the work and agreed to be accountable for all aspects of the work.

Ethics was approved by the Human Research Ethics Committee of Victoria University, Australia (ethics number HREC15-299). In addition, ethics was approved from Prolipsis Medical Centre Greece (number 1135-12/06/2006). Informed consent was obtained from all patients or their families/legal guardians involved in the study. The study was carried out in accordance with the guidelines of the Declaration of Helsinki.

This study was supported by philanthropic funds received from The Thelma and Paul Constantinou Foundation, Graeme & Angelina Wise, and from AHEPA Victoria Unit Athena 2 Daughters of Penelope. N.K was a recipient of an Australian Postgraduate Research Award.

The authors declare no conflict of interest.