Increased expression of senescence markers P14ARF and p16 INK4a in breast cancer is associated with increased risk of disease recurrence and poor survival outcome

Aims: Breast cancer is a hormonally driven disease. Cellular senescence is an age-related irreversible cell cycle arrest at the G1 phase upon induction. This study aimed to characterize the expression patterns of senescence markers p14ARF, p16INK4a and p21WAF1/Cip1 during breast cancer progression in a large patient cohort. Methods and results: We conducted a retrospective study of 1080 patients with invasive ductal carcinoma, no special type, over an 11 year period. We performed immunohistochemical staining on tissue microarrays that include normal, benign hyperplasia, ductal carcinoma in situ and invasive ductal carcinoma from each patient. Invasive ductal carcinomas demonstrated greater expression of p14ARF and p16INK4a, but lower expression of p21WAF1/Cip1 when compared to non-malignant tissues. There was significant correlation between normal, benign, pre-invasive and malignant tissues with p14ARF, p16INK4a and p21WAF1/Cip1 expression (p<0.05). Univariate comparison showed correlation between strong p16INK4a expression with poor survival (p=0.000) and increased risk of relapse (p=0.000), while high p14ARF expression correlated only with increased risk of relapse (p=0.038). Multivariate analysis showed p16INK4a as an important prognostic factor for overall survival (p=0.011) and disease free survival (p=0.004), with p14ARF also a significant prognostic factor for disease free survival (p=0.043). Moreover, patients displaying both strong p16 and p14 expressions had an adjusted 3-fold increased risk of disease recurrence (p<0.05) and 2-fold increased risk of all-cause related death (p<0.05). Conclusions: These finding suggest p16INK4a and p14ARF expression may play an important role in the progression of proliferative breast tissue to invasive cancer, and may be useful as prognostic factors.