Breast cancer is a heterogeneous disease with distinct clinical subtypes, categorized by hormone receptor status, which exhibits different prognoses and requires personalized treatment approaches. These subtypes included luminal A and luminal B, which have different prognoses. Breast cancer development and progression involve many factors, including interferon-gamma (IFNG). Moreover, single nucleotide polymorphisms (SNPs) in IFNG have been associated with cancer risk. However, the functional role of IFNG polymorphisms in primary breast cancer subtypes, luminal A and luminal B, is unclear.

A total of 138 breast cancer tissues were acquired: 81 had luminal A, 42 had luminal B, 10 had triple-negative, and 3 had human epidermal growth factor receptor 2 (HER2) subtypes, while 2 had missing data. The tissues were evaluated in relation to luminal A and luminal B primary breast cancer subtypes. DNA was extracted from freshly frozen samples, and three SNPs (rs1861493 (chr12:68157416 (GRCh38.p13)), rs1861494 (chr12:68157629 (GRCh38.p13)) and rs2430561 (chr12:68158742 (GRCh38.p13))) in the IFNG gene were selected and evaluated based on previously published associations with cancer or other diseases.

The data showed that IFNG polymorphisms rs1861493 and rs1861494 were associated with breast cancer risk, with the A allele of rs1861493 and T allele of rs1861494 being noted as the risk alleles. Furthermore, the IFNG polymorphism rs2430561 was associated with breast cancer risk, with the A allele being the risk allele. In addition, the risk alleles were more prevalent in the more aggressive subtype, luminal B breast cancer, compared to luminal A. Similarly, the rs2430561 AA genotype was associated with the breast cancer severity.

IFNG polymorphisms rs1861493, rs1861494, and rs2430561, with their respective risk alleles, are associated with increased breast cancer risk and severity. These risk alleles are more prevalent in the aggressive luminal B subtype compared to luminal A, indicating their role in both the prevalence and prognosis of breast cancer in a Greek population.