In a cross-sectional study of 138 women with no history of breast cancer who underwent reduction mammoplasty, we studied breast cancer risk factors, plasma and breast folate concentrations, variation in one-carbon metabolism genes, p16(INK4a) promoter methylation and P16 protein expression.
The results of this study revealed a paucity of mutations in CDKN2A/ARF suggesting that in the Polish population this gene does not contribute significantly to early-onset breast cancer, pancreatic cancer and malignant melanoma.
Five further patients (5 of 83; 6% of cohort) were found to harbor pathogenic variants in genes lacking a firm association with breast cancer susceptibility to date (i.e., Fanconi pathway genes, RECQ family genes, CDKN2A/p14<sup>ARF</sup>, and RUNX1).
The SNP and CGH array both detected cytogenetic abnormalities commonly found in breast cancer: amplification of chromosomes 11q13-14.1, 17q and 20q containing cyclin D1, BCAS1 and 3 (Breast Cancer Amplified Sequence) and AIB1 (Amplified in Breast cancer) genes; losses at 6q, 9p and X chromosomes, which included ERalpha (Estrogen Receptor alpha) and p16 ( INK4A ) genes.
CDKN2 is not deleted with high frequency in primary breast carcinomas, and the p16 gene does not play a role in breast carcinogenesis via this mechanism.
Our analysis of the RB-positive MCF-7 and ZR75.1 breast cancer cell lines revealed a lack of endogenous p16 protein expression as a result of the homozygous deletion and methylation of the p16 gene at the CDKN2A locus, respectively.
We report for the first time that ADP-ribosylation factor 1 (ARF1) is the most amplified gene in ARF gene family in breast cancer, and high-level amplification of ARF1 is associated with increased mRNA expression and poor outcomes of patients with breast cancer.
We showed a meaningful relationship of CDKN2A/B with the risk of breast cancer, cancer, showing the importance of studies in great sample size and several centers for studying the value of the marker as a risk classification in the management of patients with breast cancer.
Methylation of p16 was associated with a known BRCA1 mutation (P = 0.001, P < 0.001, and P < 0.001 for breast, duct, and sample levels, respectively) and women with a history of contralateral BC (P = 0.001 and P < 0.001 for duct and sample levels, respectively).
These results indicate that cytoplasmic accumulation of the p16 protein identifies a subset of highly malignant breast carcinomas with accelerated tumour proliferation and other unfavourable parameters in breast cancer.
Despite the frequent deletion of INK4 in breast cancer cell lines, no evidence was obtained for INK4 deletions in DNA from 45 primary breast carcinomas.
These results indicate that concomitant overexpression of p16INK4a and p73 may be involved in breast cancer and associated with poor tumor characteristics.
The Ink4a/alternative reading frame (ARF) locus encodes the p16(INK4a) and p14(ARF) (murine p19(ARF)) proteins. p16(INK4a) is deleted in 40-60% of breast cancer cell lines, and p16(INK4a) inactivation by DNA methylation occurs in < or =30% of human breast cancers.
Methylation techniques have shown that these epigenetic changes commonly occur at the same frequency in numerous genes, both well-known ( FHIT, APC, p16 ) and recently discovered ( TMS1, RASSF1 ) in non-small cell lung cancer and in breast cancer.