Abstract 1680: Targeting subcellular localization of Kaiso to limit dissemination through MAPK signaling

Breast cancer is the second most commonly diagnosed cancer among American women. The American Cancer Society has estimated over 230,000 new cases of breast cancer, and over 40,000 deaths for the year 2015. Unfortunately, metastasis is the major contributor for the significant number of these deaths. The Epithelial-Mesenchymal Transition (EMT) is promoted by the Master Regulator known as Kaiso, a transcriptional repressor that is a member of the BTB/POZ family of zinc finger transcription factors. We have previously demonstrated that Epidermal Growth Factor Receptor (EGFR) signaling shuttles Kaiso into the nucleus, although, its mechanism is still not understood. EGFR signaling activates multiple downstream signaling cascades including the MAP Kinase cascade, which has a significant influence on proliferation, cell adhesion, gene expression, and cell survival. Mesenchymal cells demonstrate high levels of MAPK activity and disruption or inhibition of the cascade has proven to be a method for decreasing tumor growth. Therefore we hypothesize that subcellular localization and expression of Kaiso is modulated by EGFR induced MAPK activity. Using the TCGA Breast cancer dataset, we observed that Kaiso was altered in about 11% of patients, compared to 15% of E-cad expression and 13% of MAPK3 of 959 patients/cases of Breast cancers. MAPK3 (eRK1); MAPK6, MAPK7, MAPK9 AND MAPK14 (p38) seems to have trends in mutual exclusivity or co-occurrence with Kaiso (ZBTB33). To determine if MAPK3 is responsible for increased Kaiso expression, MCF-7 cells, which express low levels of Kaiso in the cytoplasm, were treated with 10ng/ml of EGF in the presence or absence of MAPK inhibitor, 20μM PD98093. EGF stimulation caused robust increase in Kaiso protein expression, while PD98093 inhibited EGF induced expression. Similarly, in Kaiso overexpressing, MDA-MB-231, blocking EGFR kinase activity with 500nM PD153035 resulted in an opposite effect as EGF stimulation in MCF-7 cells. Furthermore, we observed a significant decrease in p-ERK expression, re-expression of E-cadherin, and low EGFR expression levels in sh-Kaiso MDA-MB-231 cells compared to sh-Scr cells. The decreased p-ERK expression in sh-Kaiso MDA-MB-231 cells was also associated with decreased expression of mesenchymal markers ZEB1, ZEB2, Twist and SNAIL at both the mRNA and protein levels compared to the scrambled control. Similarly, we observed significant decrease in the somatic cell reprogramming factors Klf4, Oct4, Nanog expression in sh-Kaiso MDA-MB-231 as well, which coincide with a reversal of EMT. To our knowledge, this is the first study to investigate the molecular mechanism and/or functional consequences of increased Kaiso expression in breast cancer, and highlights the multiple roles that Kaiso plays in promoting aggressive disease. Citation Format: Shweta Tripathi, Balasubramanyam Karanam, Bo Ma, Alan Wells, Clayton Yates. Targeting subcellular localization of Kaiso to limit dissemination through MAPK signaling. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1680.