Abstract: Objective To investigate the expression of S-phase kinase-associated protein 2 (SKp2), P27Kip1, and human leukocyte antigen (HLA)-DRA protein in cancer tissues of elderly patients with colorectal cancer (CRC) and their relationship with prognosis. Methods From January 2019 to May 2021, 154 elderly CRC patients who were adimitted to Linxi Hospital of Kailuan General Hospital were enrolled in this study. Immunohistochemistry was applied to detect the expression of SKp2, P27Kip1, and HLA-DRA proteins in the cancer tissues and adjacent tissues of elderly CRC patients. Patients were followed up for 3 years, and Kaplan-Meier method was used to plot the survival curves of the patients with positive expression and negative expression of SKp2, P27Kip1 and HLA-DRA in the cancer tissue. Multivariate Cox regression was applied to analyze the influencing factors of prognosis in the elderly CRC patients. Results Compared with adjacent tissues, the positive expression rates of SKp2 and HLA-DRA proteins were higher, and the positive expression rate of P27Kip1 was lower in CRC cancer tissues (P<0.001). The expression of SKp2 and HLA-DRA in the elderly CRC patients was related to the degree of tumor differentiation in the cancer tissue (P<0.01), the expression of P27Kip1 was related to the maximum tumor diameter in the cancer tissue (P<0.05), and the expression of SKp2, P27Kip1, and HLA-DRA was related to TNM staging in the cancer tissue (P<0.01). During the 36-month follow-up, 5 cases were lost to follow-up, 97 patients survived (survival group), and 52 patients died (death group). Compared with the survival group, the proportions of poorly differentiated, TNM stage Ⅲ-Ⅳ, SKp2 positive expression, and HLA-DRA positive expression in the death group were significantly higher (P<0.05), while the proportion of P27Kip1 positive expression was significantly lower (P<0.01). The 3-year overall survival rate of the patients with SKp2 positive expression was lower than that of the patients with SKp2 negative expression (57.38% vs 84.38%, P<0.01); the 3-year overall survival rate of the patients with P27Kip1 positive expression was higher than that of the patients with P27Kip1 negative expression (77.55% vs 56.19%, P<0.01); the 3-year overall survival rate of the patients with positive expression of HLA-DRA was lower than that of the patients with negative expression (57.52% vs 78.05%, P<0.01). Multivariate Cox regression showed that low differentiation (HR=1.213), TNM stage Ⅲ-Ⅳ (HR=1.837), SKp2 positivity (HR=1.465), and HLA-DRA positivity (HR=1.224) were independent risk factors for poor prognosis in the elderly CRC patients, while P27Kip1 positivity (HR=0.952) was a protective factor. Conclusions The positive expression rates of SKp2 and HLA-DRA are high in the cancer tissues of elderly patients with CRC, while the positive expression rate of P27Kip1 is low. The expression of SKp2, P27Kip1 and HLA-DRA is closely related to the pathological characteristics and prognosis of the patients with CRC.

Key words: colorectal cancer, prognosis, S-phase kinase-associated protein 2, P27Kip1, human leukocyte antigen DRA, aged