Comparative analysis of radiosensitizers for K-RAS mutant rectal cancers
Laura B Kleiman1, Angela M Krebs2, Stephen Y Kim1
1Molecular Pathology Unit, Center for Cancer Research and Center for Systems Biology, Massachusetts General Hospital, Charlestown, Massachusetts, United States of America.
Abstract:
Approximately 40% of rectal cancers harbor activating K-RAS mutations, and these mutations are associated with poor clinical response to chemoradiotherapy. We aimed to identify small molecule inhibitors (SMIs) that synergize with ionizing radiation (IR) ("radiosensitizers") that could be incorporated into current treatment strategies for locally advanced rectal cancers (LARCs) expressing mutant K-RAS. We first optimized a high-throughput assay for measuring individual and combined effects of SMIs and IR that produces similar results to the gold standard colony formation assay. Using this screening platform and K-RAS mutant rectal cancer cell lines, we tested SMIs targeting diverse signaling pathways for radiosensitizing activity and then evaluated our top hits in follow-up experiments. The two most potent radiosensitizers were the Chk1/2 inhibitor AZD7762 and the PI3K/mTOR inhibitor BEZ235. The chemotherapeutic agent 5-fluorouracil (5-FU), which is used to treat LARC, synergized with AZD7762 and enhanced radiosensitization by AZD7762. This study is the first to compare different SMIs in combination with IR for the treatment of K-RAS mutant rectal cancer, and our findings suggest that Chk1/2 inhibitors should be evaluated in new clinical trials for LARC.
Insights
This study identified Chk1/2 inhibitors as potent radiosensitizers for K-RAS mutant rectal cancer. Combining these inhibitors with chemotherapy may improve treatment response for locally advanced rectal cancers.
Area of Science:
- Oncology
- Molecular Biology
- Radiotherapy
Background:
- Activating K-RAS mutations occur in ~40% of rectal cancers, correlating with poor chemoradiotherapy response.
- Locally advanced rectal cancer (LARC) treatment strategies need improvement for K-RAS mutant tumors.
Purpose of the Study:
- Identify small molecule inhibitors (SMIs) that synergize with ionizing radiation (IR) to enhance radiosensitization in K-RAS mutant rectal cancer.
- Evaluate potential radiosensitizers for integration into LARC treatment protocols.
Main Methods:
- Developed and optimized a high-throughput screening assay for SMI and IR synergy.
- Screened SMIs targeting diverse signaling pathways in K-RAS mutant rectal cancer cell lines.
- Validated top radiosensitizing hits through follow-up experiments.
Main Results:
- The Chk1/2 inhibitor AZD7762 and PI3K/mTOR inhibitor BEZ235 demonstrated potent radiosensitizing activity.
- AZD7762 synergized with 5-fluorouracil (5-FU) and enhanced IR-induced radiosensitization.
- This is the first study comparing multiple SMIs with IR for K-RAS mutant rectal cancer.
Conclusions:
- Chk1/2 inhibitors show significant promise as radiosensitizers for K-RAS mutant rectal cancer.
- Clinical trials evaluating Chk1/2 inhibitors in combination with IR and chemotherapy for LARC are warranted.
