104P Novel TYR-peptide potential in treatment of fibrosarcoma by targeting cancer stem cells leading to overall survival

There is an urgent clinical need to develop new combination therapies for patients with refractory high grade soft tissue sarcomas, particularly fibrosarcoma. These aggressive tumors, with overall survival rates less than 30%, respond poorly to conventional therapies. Standard systemic care for these tumors includes doxorubicin (DXR). A Tyr peptide analogue (TPA), developed in our laboratory, specifically targets cancer stem cells (CSC). For the primary tumor growth model, half a million luciferase-labeled human fibrosarcoma HT1080 cells were xenografted in the quadriceps of 25-gram Nu/Nu male mice. Tumor growth was monitored by IVIS imaging. For the metastatic model, one million luciferase-labeled HT1080 cells were injected intravenously and survival assessed per UM IACUC protocol 19-079. DXR was delivered intravenously once at 15mg/kg while TPA at 0.025 mg/hour using Alzet osmotic minipumps transplanted subcutaneously. qRT-PCR, immunoblot, cell toxicity assays, tissue culture. Our results show that TPA specifically targets and significantly inhibits cancer stem cell growth, cell maintenance by drastically reducing expression of the polycomb group protein enhancer of zester (EZH2) and its downstream targets ALDH1A1, a well-characterized cancer stem cell marker, along with embryonic transcription factor Nanog. In addition, TPA and DXR used in combination for the treatment of relapsed DXR-treated fibrosarcoma led to a seven-fold decrease in primary tumor growth. In an experimental metastatic model, there was more than two-fold decrease in tumor growth with 100% survival observed at 58 days for the same combo group. Tyr peptide also efficiently inhibited other connective tissue malignancies tested in vitro- other types of sarcoma and acute lymphocytic leukemia. Treatment-refractory cancer, which is associated with drug resistance, is thought to stem from cellular heterogeneity and driven by a small population of CSCs. Our studies showed that TPA, which targets CSC, expands the therapeutic efficacy of DXR both in vitro and in vivo, leading to decreased tumor burden and increased survival.