Colorectal cancer cell lines made resistant to SN38-and Oxaliplatin: Roles of altered ion transporter function in resistance?

Colorectal cancer (CRC) is the 3rd most common cancer globally, with 5year survival rates of ~50%. Response rates to standard treatments (irinotecan (SN38) or Oxaliplatin (Oxp)) are 31–56% and drug resistance is a major problem. Thus, we established in vitro CRC models to investigate SN38 and Oxp resistance in HCT-116, HT-29 and LoVo cells. Microarray analysis and qPCR validation showed that mRNA expression of glutamate transporters SLC1A1 and SLC1A3 were markedly altered in resistant cells. Remarkably, mRNA levels of SLC1A3 were increased by ~40-and ~2500-fold in SN38-and Oxp-resistant HT29 cells, respectively. Studies are ongoing to assess glutamate uptake in parental and resistant CRC cells and the effect of inhibition/knockdown of SLC1A1 and -3 on SN38- and Oxp resistance.

In conclusion, SN38-and Oxp-resistance in CRC cells is associated with SLC1A1 and -3 dysregulation. As these transporters have not previously been implicated in SN38 or Oxp resistance and are generally restricted to the CNS, they are potential novel biomarkers for resistance and interesting candidates for therapeutic targeting.