PIK3CA dependence and sensitivity to therapeutic targeting in urothelial carcinoma.

R L Ross,S D Shnyder,L Kettlewell,M A Knowles,O Alder,C D Hurst,H R Mcpherson

doi:10.1186/s12885-016-2570-0

R L Ross, S D Shnyder + Show 5 more

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https://doi.org/10.1186/s12885-016-2570-0

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Abstract

BackgroundMany urothelial carcinomas (UC) contain activating PIK3CA mutations. In telomerase-immortalized normal urothelial cells (TERT-NHUC), ectopic expression of mutant PIK3CA induces PI3K pathway activation, cell proliferation and cell migration. However, it is not clear whether advanced UC tumors are PIK3CA-dependent and whether PI3K pathway inhibition is a good therapeutic option in such cases.MethodsWe used retrovirus-mediated delivery of shRNA to knock down mutant PIK3CA in UC cell lines and assessed effects on pathway activation, cell proliferation, migration and tumorigenicity. The effect of the class I PI3K inhibitor GDC-0941 was assessed in a panel of UC cell lines with a range of known molecular alterations in the PI3K pathway.ResultsSpecific knockdown of PIK3CA inhibited proliferation, migration, anchorage-independent growth and in vivo tumor growth of cells with PIK3CA mutations. Sensitivity to GDC-0941 was dependent on hotspot PIK3CA mutation status. Cells with rare PIK3CA mutations and co-occurring TSC1 or PTEN mutations were less sensitive. Furthermore, downstream PI3K pathway alterations in TSC1 or PTEN or co-occurring AKT1 and RAS gene mutations were associated with GDC-0941 resistance.ConclusionsMutant PIK3CA is a potent oncogenic driver in many UC cell lines and may represent a valuable therapeutic target in advanced bladder cancer.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-016-2570-0) contains supplementary material, which is available to authorized users.

Highlights

Many urothelial carcinomas (UC) contain activating PIK3CA mutations
Following selection of mass populations of resistant cells, p110α protein levels were reduced by 42–92 % in cells expressing each of the shRNAs relative to controls and these levels remained constant through sequential cell passages, demonstrating efficient and stable PIK3CA knockdown (Fig. 1a & b)
Expression of E545K mutant PIK3CA in TERT-NHUC induces phosphatidylinositol 3-kinase (PI3K) pathway activation and increases cell proliferation, migration and resistance to anoikis [32]. We tested whether these phenotypes are affected by knockdown of mutant PIK3CA in UC cell lines

Summary

Introduction

In telomerase-immortalized normal urothelial cells (TERT-NHUC), ectopic expression of mutant PIK3CA induces PI3K pathway activation, cell proliferation and cell migration. It is not clear whether advanced UC tumors are PIK3CA-dependent and whether PI3K pathway inhibition is a good therapeutic option in such cases. 50–70 % of tumors contain mutations that are predicted to activate this pathway. These include activating mutations in PIK3CA, [8, 9] and AKT1 [10], and inactivating mutations of PTEN [11, 12], PIK3R1 [13], TSC1 and TSC2 [9, 14].

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