Serine-arginine protein kinase 1 (SRPK1) is under-expressed in mucinous colorectal cancer, and may mediate resistance to oxaliplatin.

Abstract

5-15% of all colorectal cancers (CRCs) are mucinous. Mucinous CRCs are associated with an inhibited response to standard adjuvant and neoadjuvant therapies. Serine-Arginine Protein Kinase 1 (SRPK1) is an enzyme, which modulates the activity of multiple splicing factors. SRPK1 under-expression is associated with resistance to platinum-based chemotherapeutic agents in multiple tumor types. The objectives of this study were to evaluate SRPK1 expression in mucinous CRC and to explore the potential relationship between differential SRPK1 expression and oxaliplatin resistance in mucinous CRC. Rectal cancer and CRC Tissue Microarrays (TMA) were stained with SRPK1 to compare expression between mucinous and non-mucinous tumors. SRPK1 expression was analyzed in mucinous and non-mucinous CRC cell lines. Cells were treated with oxaliplatin to explore differences in treatment response. Mucinous cells were transfected with an SRPK1 CRISPR/Cas9 lentiviral activation plasmid to investigate the relationship between SRPK1 expression and oxaliplatin resistance. The TMA cohorts included 117 patients with mucinous and 441 patients with non-mucinous CRC. SRPK1 was found to be under-expressed in both the mucinous rectal cancer (P < 0.001) and CRC cohorts (P = 0.003). On univariate analysis, SRPK1 under-expression was found to be associated with worse 5-year OS (P = 0.001). Treatment of mucinous CRC cells with oxaliplatin did not result in a significant increase in cell death (P = 0.149). However overexpression of SRPK1 following transfection with a CRISPR/CAS9 activation plasmid resulted in a significant increase in sensitivity of these cells to oxaliplatin treatment (P = 0.029). SRPK1 is under-expressed in mucinous CRC, and under-expression is associated with worse OS. This may be due to the positive effects of SRPK1 on oxaliplatin sensitivity.