Abstract 2126: PIK3CA mutation status is not involved in the response of nonsteroidal anti-inflammatory drugs in colorectal cancer cell lines
Authors: Borras-Flores Ester , Calhoun Kara , Bhatia Gita , Wu Hong , Vilar-Sanchez Eduardo 
Published: May 2015

Nonsteroidal anti-inflammatory drugs (NSAIDs) have shown a chemopreventive effect for colorectal cancer (CRC) in many epidemiological and large scale population studies. Moreover, regular use of NSAIDs has been recently associated with a reduction in the recurrence rate of CRC in patients previously diagnosed with colorectal tumors harboring PIK3CA mutations in two different retrospective analyses of large clinical cohorts. However, the mechanism by which PIK3CA mutations interacts with the mechanism of action of NSAIDs remains elusive.

Our aim was to investigate the contribution of the most common alterations detected in PIK3CA to the sensitivity of NSAIDs in CRC cell line models.

We have studied the cytotoxicity activity of two NSAIDs, Aspirin and Naproxen, in a panel of nine CRC cell lines by performing drug cytotoxicity assays. We have compared the sensitivity to Aspirin and Naproxen in cell lines grouped by the PIK3CA mutational status (wild-type versus mutant and by specific mutation hot-spots). Drug concentrations resulting in 50% growth inhibition (IC50) were determined by a curve-fitting analysis. In addition, two pairs of isogenic cell lines were used to analyze the contribution of PIK3CA mutations to drug sensitivity. One pair of each cell line contain only the mutant allele and the other the wild-type copy. The DLD-1 and HCT-116 cell line models containing only the wild-type allele were named 123 and 127, respectively. The DLD-1 and HCT-116 harboring the p.H1047R (exon 20) and p.E545K (exon 9) mutation were named 125 and 129, respectively. Moreover, modulation of classical biomarkers of the effect of NSAIDs, COX-2 and Prostaglandin E2 (PGE2) levels, was studied by qRT-PCR in treated and untreated cell lines. The ß-actin housekeeping gene was used to normalize samples and relative quantification of COX-2 and PGE2 RNA was done by the ΔΔCt approach.

PIK3CA mutant cell lines showed no significant differences in IC50 compared to wild-type cells lines. This lack of contribution of the PIK3CA mutations to the cytotoxic effect of NSAIDs was further validated in the isogenic cell line pairs. Also, in the isogenic cell lines pairs, we found a reduced expression of COX-2 and an increased expression of PGE2 when the cell lines were treated with Aspirin or Naproxen as expected based on the known effects of NSAIDs, and thus corroborating their mechanistic effect.

Therefore, we conclude that PIK3CA alterations are not correlated with sensitivity to NSAIDs. Our preclinical results do not support the epidemiological observations that PIK3CA tumors are more sensitive to NSADIS. Further in vitro and in vivo analyses to continue elucidating the contribution of the PI3K pathway to the effect of NSAIDs in CRC models are warranted.

Citation Format: Ester Borras-Flores, Kara Calhoun, Gita Bhatia, Hong Wu, Eduardo Vilar-Sanchez. PIK3CA mutation status is not involved in the response of nonsteroidal anti-inflammatory drugs in colorectal cancer cell lines. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2126. doi:10.1158/1538-7445.AM2014-2126