Functional characterization of the 19q12 amplicon in grade III breast cancers

Abstract

IntroductionThe 19q12 locus is amplified in a subgroup of oestrogen receptor (ER)-negative grade III breast cancers. This amplicon comprises nine genes, including cyclin E1 (CCNE1), which has been proposed as its 'driver'. The aim of this study was to identify the genes within the 19q12 amplicon whose expression is required for the survival of cancer cells harbouring their amplification.MethodsWe investigated the presence of 19q12 amplification in a series of 313 frozen primary breast cancers and 56 breast cancer cell lines using microarray comparative genomic hybridisation (aCGH). The nine genes mapping to the smallest region of amplification on 19q12 were silenced using RNA interference in phenotypically matched breast cancer cell lines with (MDA-MB-157 and HCC1569) and without (Hs578T, MCF7, MDA-MB-231, ZR75.1, JIMT1 and BT474) amplification of this locus. Genes whose silencing was selectively lethal in amplified cells were taken forward for further validation. The effects of cyclin-dependent kinase 2 (CDK2) silencing and chemical inhibition were tested in cancer cells with and without CCNE1 amplification.Results19q12 amplification was identified in 7.8% of ER-negative grade III breast cancer. Of the nine genes mapping to this amplicon, UQCRFS1, POP4, PLEKHF1, C19ORF12, CCNE1 and C19ORF2 were significantly over-expressed when amplified in primary breast cancers and/or breast cancer cell lines. Silencing of POP4, PLEKHF1, CCNE1 and TSZH3 selectively reduced cell viability in cancer cells harbouring their amplification. Cancer cells with CCNE1 amplification were shown to be dependent on CDK2 expression and kinase activity for their survival.ConclusionsThe 19q12 amplicon may harbour more than a single 'driver', given that expression of POP4, PLEKHF1, CCNE1 and TSZH3 is required for the survival of cancer cells displaying their amplification. The observation that cancer cells harbouring CCNE1 gene amplification are sensitive to CDK2 inhibitors provides a rationale for the testing of these chemical inhibitors in a subgroup of patients with ER-negative grade III breast cancers.

Resistance to CDK2 Inhibitors Is Associated with Selection of Polyploid Cells inCCNE1-Amplified Ovarian Cancer

“…Here, we show a dependency on CDK2, the partner protein of cyclin E1, in ovarian and other tumor types with amplification of the 19q12 locus. The essentiality of CCNE1 and CDK2 in ovarian tumors with 19q12 amplification is consistent with a recent report in breast cancer (23). Expression of other 19q12 genes may also contribute to the oncogenic effect of amplification.…”

“…Expression of other 19q12 genes may also contribute to the oncogenic effect of amplification. Suggested targets include the prosurvival protein URI1 (7,24), and CCNE1, POP4, PLEKHF1, and TSHZ3 in breast cancer (23). Furthermore, genes elsewhere in the genome such as TPX2, that we have shown to be frequently coamplified with CCNE1 (7), may function in essential cooperational networks.…”

Frequent CCNE1 amplification in endometrial intraepithelial carcinoma and uterine serous carcinoma

“…For example, in breast and ovarian cancers, in vitro silencing of CCNE1 suppresses cellular growth selectively in cells harboring CCNE1 amplification. 10,18,19 On the other hand, ectopic expression of CCNE1 increases cellular proliferation in ovarian cancer cell lines. 18 Moreover, these data support the driver role of CCNE1 amplification in cancers as cyclin E1 mediates G1/S transition through the activation of CDK2.…”

“…One of the mechanisms responsible for cyclin E1 degradation is mediated by ubiquitination through the SCF-Fbxw7 protein complex. 8 Aberrant accumulation of cyclin E1 is common in a variety of carcinomas of breast, cervix, colorectum, stomach, and ovary, 9,10 and as a result, a high level of cyclin E1 shortenings G1 phase, expedites G1/S transition and facilitates cellular proliferation. Interestingly, somatic mutations of FBXW7, a gene encoding Fbxw7, are frequently mutated in uterine serous carcinomas including those uterine serous carcinomas without CCNE1 amplification.…”

Preexisting oncogenic events impact trastuzumab sensitivity in ERBB2-amplified gastroesophageal adenocarcinoma

“…The peak of amplification identified by GISTIC included only 1 gene, CCNE1 (Supplemental Table 1). Focal amplifications of CCNE1 have been seen in genomic studies of breast cancer and uterine serous cancer (36)(37)(38).…”