Colorectal cancer (CRC) is one of the most common malignancy, and the prognosis is not still satisfactory due to treatment resistance, recurrence and distant metastasis. Cancer stem cells (CSCs)/cancer-initiating cells (CICs) is endowed with higher tumor-initiating ability, self-renewal ability and differentiation ability, and CSCs/CICs are resistant to treatments. Thus, CSCs/CICs are thought to be responsible for recurrence and distant metastasis, and eradication of CSCs/CICs is essential to cure CRCs. However, the molecular mechanisms of CSCs/CICs are remain unknown, and we aimed to elucidate molecular aspects of CR-CSCs/CICs in this study. We screened the transcriptome data of primary human CR-CSCs/CICs that we previously established, and found that LEM domain containing 1 (LEMD1) is preferentially expressed in CR-CSCs/CICs. LEMD1 belongs to cancer-testis (CT) antigen, and has five transcript variants (variant 1 [V1] - variant 5 [V5]). We found that LEMD1 V1, V2 and V3 is expressed in testis and CR-CSCs/CICs, whereas LEMD1 V4 and V5 is ubiquitously expressed. LEMD1 gene knockdown experiments using siRNAs and gene overexpression experiments revealed that LEMD1 has a role in the maintenance of CR-CSCs/CICs. These observations indicate that CR-CSC/CIC-specific LEMD1 variants are reasonable target of CR-CSC/CIC-targeted therapy.
Keywords: Cancer stem cell; Cancer/testis antigen; Colorectal cancer; LEMD1; Splicing variant.
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