PUMA–p53 Dysregulation and Ki-67 Overexpression Define Unfavorable Prognostic Signatures in Colorectal Cancer

Background/Objectives: Colorectal cancer (CRC) is the third most commonly occurring cancer. Apoptosis is a fundamental cellular process of programmed cell death, and although many pathways for inducing apoptosis may exist, only the intrinsic and the extrinsic pathways have been demonstrated in detail. This study investigated the expression of BAD, BID, BCL2, MDM2, p53, Ki-67, and PUMA in primary CRC, paired lymph node metastases, and adjacent normal mucosa, and explored their associations with clinicopathologic features and patient outcomes. Methods: One hundred thirty patients who underwent surgery for resectable CRC were included in the study. FFPE tumor tissue samples were prospectively collected and used for the construction of the ΤΜΑ blocks from primary tumour, paired lymph node metastasis, and paired normal mucosa. Immunohistochemistry for BAD, BID, BCL2, MDM2, p53, Ki-67, and PUMA antibodies was performed. Results: Univariate analysis showed reduced cancer-specific (CSS), disease-free (DFS), and overall survival (OS) in patients with lymphatic invasion, ≥4 positive lymph nodes, poorly differentiated tumors, older age (≥65), right-sided tumors, stage IIIC disease, or no chemotherapy. Multivariate analysis identified lymphovascular invasion, ≥4 metastatic nodes, and high Ki-67 as independent predictors of worse DFS and CSS, with low BAD expression additionally predicting DFS. For OS, adverse predictors included nodal burden, tumor location, absence of chemotherapy, and high p53, MDM2, and Ki-67 expression. Notably, combined high PUMA and low p53 expression independently predicted poorer CSS and OS. Conclusions: Combined high expression of PUMA with low expression of p53 as well as high expression of Ki-67, were independent unfavorable prognostic indicators for both OS and CSS. Further studies are required to clarify the prognostic and therapeutic role of these markers in CRC.