J Cancer 2015; 6(12):1306-1319. doi:10.7150/jca.13266

Research Paper

Comprehensive Two- and Three-Dimensional RNAi Screening Identifies PI3K Inhibition as a Complement to MEK Inhibitor AS703026 for Combination Treatment of Triple-Negative Breast Cancer

Jangsoon Lee1, Rachael Galloway2, Geoff Grandjean3, Justin Jacob3, Juliane Humphries1, Chandra Bartholomeusz1, Samantha Goodstal4, Bora Lim1, Geoffrey Bartholomeusz3✉, Naoto T. Ueno1✉, Arvind Rao2✉

1. Section of Translational Breast Cancer Research and Morgan Welch Inflammatory Breast Cancer Research Program and Clinic, Department of Breast Medical Oncology - Unit 1354, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX, 77030, USA;
2. Department of Bioinformatics and Computational Biology - Unit 1410, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX, 77030, USA;
3. Department of Experimental Therapeutics - Unit 1950, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX, 77030, USA;
4. EMD Serono Research & Development Institute, Inc., 45A Middlesex Turnpike, Billerica, MA, 01821, USA.

Abstract

Triple-negative breast cancer (TNBC) is a major cause of death among breast cancer patients that results from intrinsic and acquired resistance to systemic chemotherapies. To identify novel targets for effective treatment of TNBC through combination strategies with MEK inhibitor (AS703026), we used a novel method of combining high-throughput two- and three-dimensional (2D and 3D) RNAi screening. TNBC cells were transfected with a kinome siRNA library comprising siRNA targeting 790 kinases under both 2D and 3D culture conditions with or without AS703026. Molecule activity predictor analysis revealed the PI3K pathway as the major target pathway in our RNAi combination studies in TNBC. We found that PI3K inhibitor SAR245409 (also called XL765) combined with AS703026 synergistically inhibited proliferation compared with either drug alone (P < 0.001). Reduced in vitro colony formation (P < 0.001) and migration and invasion ability were also observed with the combination treatment (P<0.01). Our data suggest that SAR245409 combined with AS703026 may be effective in patients with TNBC. We conclude that a novel powerful high-throughput RNAi assays were able to identify anti-cancer drugs as single or combinational agents. Integrated and multi-system RNAi screening methods can complement difference between in vitro and in vivo culture conditions, and enriches targets that are close to the in vivo condition.

Keywords: Triple-negative breast cancer, two-dimensional RNAi screening, three-dimensional RNAi screening, SAR245409, AS703026, multicellular tumor spheroid, projection formation.

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How to cite this article:
Lee J, Galloway R, Grandjean G, Jacob J, Humphries J, Bartholomeusz C, Goodstal S, Lim B, Bartholomeusz G, Ueno NT, Rao A. Comprehensive Two- and Three-Dimensional RNAi Screening Identifies PI3K Inhibition as a Complement to MEK Inhibitor AS703026 for Combination Treatment of Triple-Negative Breast Cancer. J Cancer 2015; 6(12):1306-1319. doi:10.7150/jca.13266. Available from http://www.jcancer.org/v06p1306.htm