Abstract B037: Utilizing GSK3β and integrin inhibitors to target STAT3 activity in triple negative breast cancer
Authors: Pratt Emily A , Walker Sarah R 
Published: February 2024

Abstract
Triple negative breast cancer (TNBC) is the most aggressive subtype of breast cancer known for its high rate of recurrence and metastatic ability. Patients face a poor prognosis and the five-year survival rate for those diagnosed with metastatic TNBC is very low. The transcription factor Signal Transducer and Activator of Transcription 3 (STAT3) is constitutively active in TNBC and functions to promote proliferation and metastasis. Therefore, it is a potential therapeutic target for TNBC. We used CLUE, an online bioinformatics tool from the Broad Institute, to identify potential STAT3 inhibitors. To do this, a STAT3 gene signature generated from TNBC cells was used to query the gene signatures from drug treatments in the CLUE dataset for compounds that caused a similar signature. The hypothesis is that a drug with a similar signature to the STAT3 inhibition signature would be a potential STAT3 inhibitor. Drugs were chosen based on high similarity rating and known function. One of the top drugs we chose to pursue was TWS-119, a GSK3β inhibitor. GSK3β is a serine/threonine kinase that regulates proliferation and cell survival. TWS-119 was found to decrease the viability of MDA-MB-231, MDA-MB-468, and Hs587T TNBC cell lines. To assess the ability of TWS-119 to inhibit STAT3 activity, we used a STAT3 responsive reporter and found that TWS-119 inhibited STAT3 activity in MDA-MB-468 cells. To determine the mechanism of inhibition of STAT3 activity, we analyzed the effects of TWS-119 on STAT3 tyrosine phosphorylation. Preliminary results suggest that TWS-119 inhibits STAT3 activity via inhibition of tyrosine phosphorylation. Having determined that TWS-119 inhibited STAT3 activity, we wanted to determine if TWS-119 had any effect on TNBC migration. We found that TWS-119 reduced the migratory ability of MDA-MB-231 cells. An additional drug identified from CLUE was Cilengitide, an inhibitor of integrin ⍺vβ3 which plays an important role in proliferation and migration. While Cilengitide only slightly decreased the viability of the three different TNBC cell lines (MDA-MB-231, MDA-MB-468, Hs587T), we found that combinations of Cilengitide and TWS-119 had synergistic effects on cell viability in the TNBC cells. Preliminary western blot analysis demonstrated that the combination of both drugs reduced the level of pY-STAT3. This suggests that this combination targeting STAT3 may be a viable treatment strategy for TNBC. However, the mechanism through which these drugs interact is unknown, and the cell signaling relationship between their known targets (GSK3β and integrin ⍺vβ3) and STAT3 is unclear. We are currently working to define the mechanism of action of these combination effects in TNBC cells. Using TWS-119 and Cilengitide, we can determine the connection between integrins, GSK3β, and STAT3 to better understand proliferation and metastasis and to identify new therapeutic options for TNBC patients.
Citation Format: Emily A Pratt, Sarah R Walker. Utilizing GSK3β and integrin inhibitors to target STAT3 activity in triple negative breast cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Breast Cancer Research; 2023 Oct 19-22; San Diego, California. Philadelphia (PA): AACR; Cancer Res 2024;84(3 Suppl_1):Abstract nr B037.