Objective  This study investigated the expression level of phosphatidylserine-specific phospholipase A1 (PLA1A) in colorectal cancer (CRC) and analyzed its correlations with clinicopathological features, prognosis, and immune infiltration.

Methods The expression level of PLA1A in CRC was screened, and the influence of this expression level on patient prognosis was analyzed using bioinformatics methods. A cohort of 192 patients diagnosed with CRC at Shanxi Province Cancer Hospital from January to December 2020 were selected. The PLA1A expression level in those with CRC was determined using immunohistochemistry (IHC) and real-time quantitative reverse transcription PCR (RT-qPCR). The relationship between PLA1A level and the clinicopathological features of the patients with CRC was analyzed using the chi-square test. The expression levels of immune cell markers CD4 and CD8 as well as immunosuppressive checkpoints PD-1, TIM-3, and CTLA-4 in CRC were detected via IHC, and their correlations with PLA1A level were analyzed using the chi-square test.

Results The results of bioinformatics analysis showed that the expression level of PLA1A in CRC tissue was higher than paracancerous tissue, which correlated with overall survival (OS) (P<0.05). The IHC and RT-qPCR results showed that PLA1A expression level was significantly upregulated in CRC tissiue (P<0.05). High PLA1A level was closely associated with the TNM stage, degree of differentiation, and lymph node metastasis (P<0.05). The IHC results demonstrated that PLA1A positively correlated with the infiltrating CD8⁺T cell level (P<0.05). In addition, the elevated PLA1A levels upregulated the expressions of immunosuppressive checkpoints PD-1, TIM-3, and CTLA-4 (P<0.05).

Conclusions PLA1A is highly expressed in CRC, which is closely related to immune infiltrating cells and immunosuppressive checkpoints, suggesting that PLA1A plays an important role in immune infiltration in CRC, a finding that provides guidance in the treatment of CRC.