Elucidation of the mutational landscape of human cancer has progressed rapidly and been accompanied by the development of therapeutics targeting mutant oncogenes. However, a comprehensive mapping of cancer dependencies has lagged behind and the discovery of therapeutic targets for counteracting tumor suppressor gene loss is needed. To identify vulnerabilities relevant to specific cancer subtypes, we conducted a large-scale RNAi screen in which viability effects of mRNA knockdown were assessed for 7,837 genes using an average of 20 shRNAs per gene in 398 cancer cell lines. We describe findings of this screen, outlining the classes of cancer dependency genes and their relationships to genetic, expression, and lineage features. In addition, we describe robust gene-interaction networks recapitulating both protein complexes and functional cooperation among complexes and pathways. This dataset along with a web portal is provided to the community to assist in the discovery and translation of new therapeutic approaches for cancer.

Tankyrases (TNKS) play roles in Wnt signaling, telomere homeostasis, and mitosis, offering attractive targets for anticancer treatment. Using unbiased combination screening in a large panel of cancer cell lines, we have identified a strong synergy between TNKS and MEK inhibitors (MEKi) in KRAS-mutant cancer cells. Our study uncovers a novel function of TNKS in the relief of a feedback loop induced by MEK inhibition on FGFR2 signaling pathway. Moreover, dual inhibition of TNKS and MEK leads to more robust apoptosis and antitumor activity both in vitro and in vivo than effects observed by previously reported MEKi combinations. Altogether, our results show how a novel combination of TNKS and MEK inhibitors can be highly effective in targeting KRAS-mutant cancers by suppressing a newly discovered resistance mechanism. Cancer Res; 74(12); 3294-305. Ó2014 AACR.

Tankyrases (TNKS) play roles in Wnt signaling, telomere homeostasis and mitosis, and are therefore considered as attractive targets for anti-cancer treatment. Using unbiased combination screens in a large panel of cancer cell lines, we have identified a strong synergy between TNKS and MEK inhibitors in KRAS mutant cancer cells. Our study uncovers a novel function of TNKS in the relief of a feedback loop induced by MEK inhibition on FGFR2 signaling pathway. Moreover, dual inhibition of TNKS and MEK leads to more robust apoptosis and anti-tumor activity both in vitro and in vivo than effects observed by previously reported MEK inhibitor combinations. Altogether, our data provides a strong rationale for combined targeting of TNKS and MEK in KRAS mutant cancers. Citation Format: Wenlin Shao, Marie Schoumacher, Kristen Hurov, Joseph Lehar, Yan Yan-Neale, Yuji Mishina, Dmitriy Sonkin, Joshua Korn, Daisy Flemming, Michael Jones, Brandon Antonakos, Vessilina Cooke, Mark Stump, Nika Danial, William Sellers. Inhibiting TNKS sensitizes KRAS mutant cancer cells to MEK inhibitors by suppressing FGFR2 feedback signaling. [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 LB-107. doi:10.1158/1538-7445.AM2014-LB-107

<p>PDF file - 660KB, Supplementary Figure S1. All RAS mutant cell lines have a higher sensitivity to the TNKSi/MEKi combination. Supplementary Figure S2. Validation of TNKSi/MEKi combination in KRAS mutant cancer cells. Supplementary Figure S3. Combinations with MEK inhibitor in the SW480 cell line. Supplementary Figure S4. TNKSi/MEKi combination leads to enhanced inhibition of AKT signaling activity. Supplementary Figure S5. TNKSi potentiates MEKi by releasing a feedback loop on FGFR2 signaling. Supplementary Figure S6. Consequences of combined inhibition of TNKS and MEK on FGFR2 and AKT signaling pathways in KRAS mutant cell lines.</p>

<p>PDF file - 54KB, Chemical inhibitors used in the study.</p>