CRISPR screens identify a novel combination treatment targeting BCL-X L and WNT signaling for KRAS/BRAF-mutated colorectal cancers
Oncogene 2021 May; 40(18):3287-3302
Metastatic or recurrent colorectal cancer (CRC) patients require systemic chemotherapy, but the therapeutic options of targeted agents remain limited. CRC patients with KRAS or BRAF gene mutations exhibit a worse prognosis and are resistant to anti-EGFR treatment. Previous studies have shown that the expression of anti-apoptotic protein BCL-XL is increased in CRC patients with KRAS/BRAF mutations, suggesting BCL-XL as a therapeutic target for this subgroup. Here, we performed genome-wide CRISPR/Cas9 screens of cell lines with KRAS mutations to investigate the factors required for sensitivity to BCL-XL inhibitor ABT-263 using single-guide RNAs (sgRNAs) that induce loss-of-function mutations. In the presence of ABT-263, sgRNAs targeting negative regulators of WNT signaling (resulting in WNT activation) were enriched, whereas sgRNAs targeting positive regulators of WNT signaling (resulting in WNT inhibition) were depleted in ABT-263-resistant cells. The activation of WNT signaling was highly associated with an increased expression ratio of anti- to pro-apoptotic BCL-2 family genes in CRC samples. Genetic and pharmacologic inhibition of WNT signaling using β-catenin short hairpin RNA or TNIK inhibitor NCB-0846, respectively, augmented ABT-263-induced cell death in KRAS/BRAF-mutated cells. Inhibition of WNT signaling resulted in transcriptional repression of the anti-apoptotic BCL-2 family member, MCL1, via the functional inhibition of the β-catenin-containing complex at the MCL1 promoter. In addition, the combination of ABT-263 and NCB-0846 exhibited synergistic effects in in vivo patient-derived xenograft (PDX) models with KRAS mutations. Our data provide a novel targeted combination treatment strategy for the CRC patient subgroup with KRAS or BRAF mutations.
Jung, Hae Rim; Oh, Yumi; Na, Deukchae; Min, Seoyeon; Kang, Jinjoo; Jang, Dongjun; Shin, Seungjae; Kim, Jiwon; Lee, Sang Eun; Jeong, Eui Man; An, Joon Yong; Sung, Chang Ohk; Lee, Won-Suk; Lee, Charles; and Cho, Sung-Yup, "CRISPR screens identify a novel combination treatment targeting BCL-X L and WNT signaling for KRAS/BRAF-mutated colorectal cancers" (2021). Faculty Research 2021. 107.