Jessica M. Keilson, MD
Clinical Research Fellow
Winship Cancer Institute, Emory University
Atlanta, Georgia, United States
Biliary tract cancers (BTCs) are a group of aggressive malignancies often refractory to chemotherapeutic or targeted therapies. Identifying effective therapeutic targets remains a priority. Galectin-9 (Gal-9), the ligand to negative regulatory immune checkpoint receptor TIM-3, plays a paradoxical role in tumorigenesis. The role of Gal-9 in the setting of BTCs in not completely understood.
We examined expression patterns of total cellular Gal-9 and TIM-3 in a panel of human BTC cell lines with diverse molecular profiles via immunoblot. Soluble Gal-9 (sGal-9) was measured by enzyme-linked immunoassay (ELISA). Tetrazolium-based MTT assay was utilized to evaluate cell viability following Ab-mediated Gal-9 neutralization. Pre-treatment peripheral blood was obtained from pts with metastatic BTCs enrolled in a randomized phase II clinical trial (NCI10139) and sGal-9 levels were measured. Kaplan-Meier analysis was used to assess the association between sGal-9 levels and overall survival (OS).
Results: Human BTC cells demonstrate detectable and differential expression levels of total Gal-9 and TIM-3 proteins in vitro (Figure 1A). TIM-3 expression was not detected among extrahepatic (MzChA-1) and gallbladder cancer (WITT) cell lines. sGal-9 is secreted at variable levels (Figure 1B) and its neutralization does not affect viability. Pre-treatment peripheral blood from 76 pts (53% (n=39) intrahepatic cholangiocarcinoma, 22% (n=16) extrahepatic cholangiocarcinoma, 25% (n=18) gallbladder cancer) showed no significant difference in sGal-9 levels between disease sites (p=0.08). High baseline plasma sGal-9 levels were associated with worse OS (p=0.03)(Figure 1C).
Conclusions: Biliary tract cancer cells differentially express galectin-9 and its receptor, TIM-3, in vitro. Higher plasma levels of soluble galectin-9 are associated with worse overall survival, suggesting galectin-9 expression may be related to a more aggressive disease state. Additional work is needed to better inform the mechanistic role of the galectin-9/TIM-3 axis on disease progression and how best to leverage this pathway as a therapeutic target in the management of biliary tract cancers.