Implication of KLHL Gene Family Member KLHL5 in Colorectal Cancer Progression and Prognosis.

The KLHL gene family member KLHL5, which is a constituent factor of the RING E3 ubiquitin ligase complex, is expressed in various types of cancers and plays a role in cancer pathophysiology. In this study, we identified KLHL5 as a potential biomarker for predicting the prognosis of colorectal cancer (CRC) from 42 KLHL family genes using transcriptome profiles generated by RNA-seq analysis of The Cancer Genome Atlas colorectal adenocarcinoma (TCGA-COAD). We further investigated the implication of KLHL5 in CRC using pathological examination and bioinformatics analyses. Clinicopathological analyses revealed that KLHL5 was more highly expressed in CRC than in adjacent normal mucosa, and its expression level increased concomitantly with the CRC stage (p < 0.05). KLHL5 expression was associated with poor prognostic factors such as depth of invasion (p < 0.001), lymphovascular invasion (p = 0.029), and lymph node metastasis (p = 0.025). Notably, KLHL5 exhibited heterogeneous expression within the tumor, with pronounced expression observed at the invasive front of the tumor (p < 0.0001). Through bioinformatics analyses, we determined that elevated KLHL5 expression in CRC is significantly associated with poor prognosis. Furthermore, analysis from the Gene Expression Omnibus database indicated that KLHL5 expression was more pronounced in the common molecular subtype (CMS) 4 CRC, which is characterized as highly advanced, and the overall and recurrence-free survival rates were poor compared to other CMS groups. Our findings indicate that KLHL5 plays a pivotal role in the progression and development of CRC, and can be used as a potential biomarker and therapeutic target for CRC treatment.