Apoptosis, necroptosis and autophagy in colorectal cancer: Associations with tumor aggressiveness and p53 status

Abstract

ObjectiveCleaved caspase-3 (CC3), phosphorylated-mixed-lineage kinase domain-like protein (p-MLKL), and microtubule-associated protein-1 light chain-3B (LC3B) have pivotal functions in apoptosis, necroptosis, and autophagy, respectively. In vitro studies have shown that interaction of these proteins are complex and their roles in cancer can be influenced by many factors. However, these findings are not adequately assessed in human tissues. Here, we determined CC3, p-MLKL, and LC3B expression in colorectal cancers (CRCs), and assessed their associations with clinicopathological parameters, and with KRAS and p53 status. MethodsWe immunohistochemically assessed 113 CRC specimens for levels of CC3, p-MLKL, LC3B, and p53. KRAS gene status was analyzed using the Scorpion- amplification refractory mutation system. ResultsHigh levels of CC3 (CC3High) and LC3B (LC3BHigh) were detected in 38% and 35% of the 113 CRCs, respectively, but no or only a few p-MLKL-positive cells were observed in any of the tumors. CC3High was significantly associated with high pT status (P = 0.03), vascular invasion (P = 0.03) and high pStage (P = 0.04) and was marginally associated with lymph node (P = 0.06) and distant metastases (P = 0.06). LC3BHigh was also significantly associated with high pT status (P = 0.02) and lymphatic invasion (P = 0.002), and was marginally associated with nerve plexus invasion (P = 0.06). In combined analysis, compared with CC3Low/LC3BLow tumors, tumors that were either CC3High, LC3BHigh, or both were significantly associated with high pT status (P = 0.0007), lymphatic invasion (P = 0.03), vascular invasion (P = 0.003), distant metastasis (P = 0.04) and high pStage (P = 0.04). LC3BHigh was significantly associated with a mutant-type expression pattern of p53 (P = 0.003). ConclusionTo the best of our knowledge, this is the first study to examine the combination of CC3/LC3B and p-MLKL expression in clinical CRC samples and to correlate these expression data with clinicopathological parameters and EGFR and p53 status. Our results suggest that necroptosis is a rare process in CRC, apoptosis and autophagy are upregulated in aggressive CRCs, and p53 mutation may lead to the upregulation of autophagy.