Abstract 1884: The breast cancer gene CCDC170 regulates the Golgi-associated microtubule network and directional cell migration

Abstract

Background: Breast cancer (BCa) is a genetically heterogeneous disease and many genes contributing to BCa risk remain to be identified. Genome-Wide Association Studies (GWAS) and subsequent fine-mapping studies (>50) have strongly implicated genetic alterations at the CCDC170/C6ORF97-ESR1 locus (6q25.1) as being associated with the risk of BCa. ESR1, encoding the estrogen receptor, might be a more obvious candidate for influencing risk. Surprisingly, our analysis using genome-wide differential allele-specific expression (DASE), an indicator for BCa susceptibility, suggested that the genetic alterations of CCDC170, but not ESR1, accounts for GWAS-associated BCa risk at this locus. CCDC170 is a coiled-coiled domain-containing protein of poorly understood function. BCa-specific truncation and missense mutations in CCDC170 also have been detected, with the truncations being implicated in driving Luminal B subtype BCa. Together these findings demonstrate that the CCDC170 gene is involved in BCa, but the underlying molecular mechanisms for its role in tumorigenesis are unknown. Experimental designs and results: By using the approaches of confocal microscopy and cell imaging analysis, here we report for the first time that CCDC170 is associated with the Golgi apparatus and perinuclear microtubules (MTs), and support a role for CCDC170 in the Golgi-associated microtubule network. We have shown that overexpression of CCDC170 triggers Golgi reorganization and stabilizes Golgi-associated MTs, accompanied by dramatically increased acetylation of α-tubulin that is driven by the acetyltransferase ATAT1. The Golgi-associated MT network has been proposed to regulate cell polarity and migration. In support of this concept, we have shown that CRISPR knockout increases, and overexpression of CCDC170 decreases, BCa directional cell migration in vitro. We also found that the BCa-specific truncations result in mislocalization of CCDC170 and/or diminished stability of Golgi-associated MTs. Lastly, we identified candidate CCDC170 functional binding partners (e.g. MAP4) that are consistent with its localization and proposed function. These partners may serve to mediate the acetylation and stabilization of MTs. Conclusions: Taken together, our findings demonstrate that CCDC170 plays an essential role in Golgi-associated MT organization and stabilization, and provide a mechanism for how perturbations in CCDC170 could alter Golgi-mediated cell polarity, and thereby drive BCa and other abnormalities. This work was partially supported by the Susan G. Komen for the Cure (KG100274), NCI (CA186853), and Eileen Stein Jacoby Fund. Citation Format: Pengtao Jiang, Yueran Li, Andrey Poleshko, Valentina Medvedeva, Natalia Baulina, Yongchao Zhang, Yan Zhou, Carolyn M. Slater, Trinity Pellegrin, Jason Wasserman, Michael Lindy, Mary Daly, Richard A. Katz, Xiaowei Chen. The breast cancer gene CCDC170 regulates the Golgi-associated microtubule network and directional cell migration [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1884. doi:10.1158/1538-7445.AM2017-1884