(P 51) OVEREXPRESSION OF GLI2 IN DEDIFFERENTIATED LIPOSARCOMA TUMORS INDUCES MICROENVIRONMENT REMODELING

Objective: Liposarcoma is the most common soft tissue sarcoma, comprised of various histological subtypes that influence clinical outcomes such as metastasis and survival, with dedifferentiated liposarcoma (DDLPS) tumors being more aggressive and resistant to treatment than their well-differentiated counterparts. We have previously shown that the Hedgehog (HH) signaling is elevated in DDLPS patient tumors. Thus, we sought to further expand upon the role of HH signaling in DDLPS using both in vitro and orthotopic models.

Methods: Gli2, a transcriptional regulator of HH, expression was found to be tumor cell specific in scRNA-seq of patient tumors. We generated an SW872 DDLPS cell line overexpressing (OE) Gli2 to evaluate cellular proliferation, differentiation, and transcriptomics in vitro, as well as tumor formation and tumor-microenvironment interactions in vivo.

Results: Our results showed a marked increase in proliferation by the activation of Gli2, in addition to a noticeable loss of differentiation capacity in vitro. Upon orthotopic injection into athymic nude mice, we found that Gli2 OE resulted in larger tumor volume, collagen encapsulation of tumors, robustly increased macrophage infiltration, and a modest increase in fibroblast recruitment and PD-L1 expression. RNA sequencing of tumor cells indicated significant changes in cytokine expression which was then validated by ELISA and cytokine arrays.

Conclusion: We found that overexpression of Gli2 in DDLPS tumor cells yielded a profoundly oncogenic phenotype resulting in larger tumor growth and robust tumor microenvironment remodeling. Specifically, we found that Gli2 OE recruited robust amounts of macrophages in DDLPS, a phenotype that has been largely uncharacterized. DDLPS tumor cells overexpressing Gli2 yielded an altered cytokine and growth factor secretion profile that could implicate HH signaling as a driver of immune suppressive cell recruitment that has potential to impede therapeutic progress moving forward. This opens an avenue for exploring Gli2 or HH pathway inhibition as a combinatorial treatment for established therapies or improving response to immune checkpoint blockade in the future.