A loss-of-function genetic screening identifies novel mediators of thyroid cancer cell viability.

Maria Carmela Cantisani,Olli Pekka Kallioniemi,Niko Sahlberg,Chiara Allocca,Vidal Fey,Merja Perälä,Mikko O Laukkanen,Francesco Merolla,Fulvio Basolo,Alessia Parascandolo,Massimo Santoro,Maria Domenica Castellone

doi:10.18632/oncotarget.8577

Abstract

RET, BRAF and other protein kinases have been identified as major molecular players in thyroid cancer. To identify novel kinases required for the viability of thyroid carcinoma cells, we performed a RNA interference screening in the RET/PTC1(CCDC6-RET)-positive papillary thyroid cancer cell line TPC1 using a library of synthetic small interfering RNAs (siRNAs) targeting the human kinome and related proteins. We identified 14 hits whose silencing was able to significantly reduce the viability and the proliferation of TPC1 cells; most of them were active also in BRAF-mutant BCPAP (papillary thyroid cancer) and 8505C (anaplastic thyroid cancer) and in RAS-mutant CAL62 (anaplastic thyroid cancer) cells. These included members of EPH receptor tyrosine kinase family as well as SRC and MAPK (mitogen activated protein kinases) families. Importantly, silencing of the identified hits did not affect significantly the viability of Nthy-ori 3-1 (hereafter referred to as NTHY) cells derived from normal thyroid tissue, suggesting cancer cell specificity. The identified proteins are worth exploring as potential novel druggable thyroid cancer targets.

Highlights

Thyroid cancer is the most common endocrine malignancy, whose incidence has been steadily increasing over the past 30 years [1,2,3]
To identify novel kinases required for the viability of thyroid carcinoma cells, we performed a RNA interference screening in the RET/PTC1(CCDC6RET)-positive papillary thyroid cancer cell line TPC1 using a library of synthetic small interfering RNAs targeting the human kinome and related proteins
The library included two independent small interfering RNAs (siRNAs) targeting each transcript and negative controls consisting of siRNAs targeting green fluorescent protein (GFP), eight non targeting scrambled sequences, as well as buffer alone

Summary

Introduction

Thyroid cancer is the most common endocrine malignancy, whose incidence has been steadily increasing over the past 30 years [1,2,3]. Most common thyroid cancer types arise from follicular epithelial cells and are classified in well-differentiated papillary (PTC) and follicular (FTC), poorly differentiated (PDC), and anaplastic (undifferentiated) (ATC) carcinoma; PTC accounts for the vast majority of thyroid cancer cases [1,2,3]. Oncogenic conversion of kinases involved in the MAPK (mitogen activated protein kinases) and PI3K (phosphatidyl-inositol-3-kinase)/AKT signaling cascades occurs in thyroid cancer [1,2,3,4]. Mutations of RAS, an upstream activator of both MAPK and PI3K, are common in FTC and in follicular-variant PTC [5,6,7]. Mutations or copy number alterations of PI3K and AKT are found in ATC and radioiodine-refractory thyroid cancer [3, 8,9,10]

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Conclusion