Abstract PO4-24-04: Identifying the interactome of TACC3, a major driver in aggressive cancer cells with centrosome amplification
Authors: Saatci Ozge , Akbulut Ozge , Cetin Metin , Sikirzhytski Vitali , Uner Meral , Lengerli Deniz , O’Quinn Elizabeth C. , Romeo Martin J. , Caliskan Burcu , Banoglu Erden , Aksoy Sercan , Uner Aysegul , Sahin Ozgur 
Published: May 2024

Abstract
Transforming Acidic Coiled-Coil Containing Protein 3 (TACC3) is a centrosome- and spindle-associated protein that drives the growth of highly aggressive tumors, such as those with centrosome amplification (CA). In recent years, it has become apparent that TACC3 not only functions at the centrosomes and spindles but may also have many other non-canonical functions facilitating the growth of tumors. Given the multifaceted roles of TACC3 in driving tumor aggressiveness, the identification of novel interactors of TACC3 that are responsible for mediating key TACC3-driven processes is crucial. This will not only uncover novel drug targets but will also expand the patient subpopulations that can benefit from TACC3 inhibition. Here, we characterized the cancer cells with CA in terms of their dependency on TACC3 for executing distinct cellular processes depending on the cell cycle phase. We demonstrated that TACC3 is strongly upregulated in cancers with CA at mRNA and protein levels and associated with worse clinical outcome in highly aggressive patient subpopulations, especially in TNBC. We further demonstrated that in mitotic cancer cells with CA, TACC3 is localized at the centrosomes in a complex with KIFC1, thus mediating the clustering of extra centrosomes to enable bipolar spindle formation and faithful mitosis. We showed that inhibiting TACC3 blocks the interaction between TACC3 and KIFC1, thus leading to mitotic cell death in the highly TACC3-dependent cancer cells with CA. While TACC3-KIFC1 complex is needed for mitotic cancer cells with CA, we found that in CA-bearing interphase cells, TACC3 interacts with HDAC2 and MBD2, the two major components of the chromatin remodeling NuRD complex within the nucleus. Inhibiting TACC3 prevented its nuclear localization, thus unloading the NuRD complex from the chromatin, leading to transcription of key tumor suppressors driving G1 arrest and apoptosis. To obtain the proteome-wide interaction network of TACC3 in these highly TACC3-dependent mitotic and interphase cancer cells with CA, we mapped the TACC3 interactome using the state-of-the-art APEX2 method. This uncovered potentially novel partners of TACC3 that could be critical for the survival of mitotic and interphase cancer cells with CA. We performed an extensive bioinformatic analysis to identify the most clinically relevant interactors in the context of cancers with CA. We generated correlation matrices of the mitotic and interphase-specific interactors and coupled them with pathway enrichment analysis to identify the key processes that the interactors are potentially involved in. Altogether, our results map, for the first time, the novel cell cycle-dependent TACC3 interactome in cancer cells with CA. Our results support targeting this multi-functional protein and hold great promise to improve clinical outcome in these highly aggressive cancers given the availability of the first-in-class IND-approved TACC3 inhibitor.
Citation Format: Ozge Saatci, Ozge Akbulut, Metin Cetin, Vitali Sikirzhytski, Meral Uner, Deniz Lengerli, Elizabeth C. O’Quinn, Martin J. Romeo, Burcu Caliskan, Erden Banoglu, Sercan Aksoy, Aysegul Uner, Ozgur Sahin. Identifying the interactome of TACC3, a major driver in aggressive cancer cells with centrosome amplification [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-24-04.