American Association for Cancer Research
00085472can152201-sup-154000_1_supp_3218404_nxf4q4.pptx (4.81 MB)

Supplementary Figures 1 through 17 and Supplementary Tables 1 and 2 from Activating Mutations in PIK3CB Confer Resistance to PI3K Inhibition and Define a Novel Oncogenic Role for p110β

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posted on 2023-03-30, 23:45 authored by Yoshito Nakanishi, Kimberly Walter, Jill M. Spoerke, Carol O'Brien, Ling Y. Huw, Garret M. Hampton, Mark R. Lackner

Supplementary Figure S1. Inhibition of AKT and S6 phosphorylation. Supplementary Figure S2. Cell growth inhibition by a panel of compounds. Supplementary Figure S3. Effect of GDC-0980 on AKT and S6 phosphorylation. Supplementary Figure S4. Cell growth inhibition by a panel of compounds. Supplementary Figure S5. Inhibition of AKT phosphorylation. Supplementary Figure S6. Cell growth inhibition by a panel of anti-cancer agents. Supplementary Figure S7. The alignment of C-terminus of Human p110 family. Supplementary Figure S8. Droplet digital PCR (ddPCR) detection of PIK3CB D1067Y mutation. Supplementary Figure S9. Detection of copy number variation. Supplementary Figure S10. A. Cell growth inhibition by GDC-0941. B. Droplet digital PCR (ddPCR) analysis of PTEN-null GDC-0941 resistant cell lines. Supplementary Figure S11. Droplet digital PCR detection of PIK3CB D1067V mutation. Supplementary Figure S12. PIK3CB mutant expressing EVSA-T cells are less sensitive to PI3K inhibitors. Supplementary Figure S13. Inhibition of AKT and S6 phosphorylation. Supplementary Figure S14. p110β dependency of A498. Supplementary Figure S15. ATP competition assay. Supplementary Figure S16. Relative quantification of baseline AKT phosphorylation levels in EVSA-T parental cells and resistant clones. Supplementary Figure S17. Signal profile in Rat-2 stable cell lines. Supplementary Table S1 Compound list. Supplementary Table S2 Whole exome sequencing list of genes mutated in EVSA-T GDC-0941 resistant cells.


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Activation of the PI3K pathway occurs commonly in a wide variety of cancers. Experience with other successful targeted agents suggests that clinical resistance is likely to arise and may reduce the durability of clinical benefit. Here, we sought to understand mechanisms underlying resistance to PI3K inhibition in PTEN-deficient cancers. We generated cell lines resistant to the pan-PI3K inhibitor GDC-0941 from parental PTEN-null breast cancer cell lines and identified a novel PIK3CB D1067Y mutation in both cell lines that was recurrent in cancer patients. Stable expression of mutant PIK3CB variants conferred resistance to PI3K inhibition that could be overcome by downstream AKT or mTORC1/2 inhibitors. Furthermore, we show that the p110β D1067Y mutant was highly activated and induced PIP3 levels at the cell membrane, subsequently promoting the localization and activation of AKT and PDK1 at the membrane and driving PI3K signaling to a level that could withstand treatment with proximal inhibitors. Finally, we demonstrate that the PIK3CB D1067Y mutant behaved as an oncogene and transformed normal cells, an activity that was enhanced by PTEN depletion. Collectively, these novel preclinical and clinical findings implicate the acquisition of activating PIK3CB D1067 mutations as an important event underlying the resistance of cancer cells to selective PI3K inhibitors. Cancer Res; 76(5); 1193–203. ©2016 AACR.