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HER2/Neu tumorigenesis and metastasis is regulated by E2F activator transcription factors.

ABSTRACT: HER2/Neu is amplified and overexpressed in a large proportion of human breast cancers, but the signaling pathways that contribute to tumor development and metastatic progression are not completely understood. Using gene expression data and pathway signatures, we predicted a role for activator E2F transcription factors in Neu-induced tumors. This was genetically tested by interbreeding Neu transgenics with knockouts of the three activator E2Fs. Loss of any E2F delayed Neu-induced tumor onset. E2F1 loss accelerated tumor growth, while E2F2 and E2F3 loss did not. Strikingly, it was observed that loss of E2F1 or E2F2 significantly reduced the metastatic capacity of the tumor and this was associated with a reduction in circulating tumor cells in the E2F2 knockout. Gene expression analysis between the tumors in the various E2F-mutant backgrounds revealed that there was extensive compensation by other E2F family members in the individual knockouts, underscoring the importance of the E2Fs in HER2/Neu-induced tumors. Extension to HER2-positive (HER2+) human breast cancer revealed a number of HER2+ subtypes based on E2F activity with differences in relapse-free survival times. Taken together, these data demonstrate that the E2F transcription factors are integral to HER2+ tumor development and progression.

SUBMITTER: Andrechek ER

PROVIDER: S-EPMC4067469 | biostudies-literature | 2015 Jan

REPOSITORIES: biostudies-literature

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HER2/Neu tumorigenesis and metastasis is regulated by E2F activator transcription factors.

Andrechek E R ER

Oncogene 20131223 2

HER2/Neu is amplified and overexpressed in a large proportion of human breast cancers, but the signaling pathways that contribute to tumor development and metastatic progression are not completely understood. Using gene expression data and pathway signatures, we predicted a role for activator E2F transcription factors in Neu-induced tumors. This was genetically tested by interbreeding Neu transgenics with knockouts of the three activator E2Fs. Loss of any E2F delayed Neu-induced tumor onset. E2F ...[more]

PMID: 24362522

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Project description:IntroductionRho GTPases are overexpressed and hyperactivated in human breast cancers. Deficiency of p190B RhoGAP, a major inhibitor of the Rho GTPases, inhibits mouse mammary tumor virus long terminal repeat (MMTV)-Neu/ErbB2 mammary tumor formation and progression in part through effects within the stromal environment, suggesting that p190B function is pro-tumorigenic. To further investigate the potential pro-tumorigenic actions of p190B, we examined the effects of exogenous p190B expression within the mammary epithelium on MMTV-Neu tumor formation and progression.MethodsTetracycline-regulatable p190B transgenic mice were bred to MMTV-Neu mice, and the effects of exogenous p190B expression on tumor latency, multiplicity, growth rates, angiogenesis, and metastasis were examined. The effects of exogenous p190B expression on cell-matrix adhesion and invasion were tested using non-transformed primary mammary epithelial cells (MECs). Rho GTPase activity, oxidative stress as an indicator of reactive oxygen species (ROS) production, and downstream signaling pathways were analyzed.ResultsAltered p190B expression resulted in a 2-fold increase in tumor multiplicity and a 3-fold increase in metastases compared to control mice indicating that exogenous p190B expression in the mammary epithelium promotes MMTV-Neu mammary tumor formation and progression. Interestingly, non-transformed primary MECs expressing exogenous p190B displayed increased adhesion to laminin and type IV collagen and formed invasive structures in a three-dimensional culture assay. Ras related C3 botulinum toxin 1 (Rac1)-GTP levels were elevated in p190B transgenic tumors whereas Ras homologous A (RhoA) and cell division cycle 42 (Cdc42)-GTP levels were not significantly altered. Rac1 activity affects production of ROS, which regulate transformation, metastasis, and oxidative stress. Protein carbonylation, which is indicative of oxidative stress, was elevated 1.75-fold in p190B transgenic tumors as compared to control tumors suggesting that exogenous p190B expression may affect Rac1-dependent ROS production.ConclusionsThese studies indicate that paradoxically, p190B RhoGAP, a major inhibitor of the Rho GTPases in vitro, has pro-tumorigenic functions that enhance MMTV-Neu induced mammary tumor formation and metastasis. Furthermore, exogenous p190B expression enhances cell adhesion and invasion, which may facilitate metastasis. Rac1 activity and oxidative stress are elevated in tumors expressing exogenous p190B suggesting that p190B may promote tumorigenesis through a Rac1/ROS dependent mechanism.

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HER2/Neu tumorigenesis and metastasis is regulated by E2F activator transcription factors.

Publications

HER2/Neu tumorigenesis and metastasis is regulated by E2F activator transcription factors.

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