lncRNA, PVT-1, controls tumorigenesis and cancer stem-like phenotypes in osteosarcoma through PI3K/TSC2.
e23512 Background: Osteosarcoma is the most common pediatric bone cancer and a key genetic characteristic of this particular malignancy is its complex karyotype. Specifically it has been reported that 40% of osteosarcoma patients’ present with 8q24 amplification. The presence of this specific amplification has been previously associated with a high rate of relapse and poor prognosis for osteosarcoma patients. Within this amplicon resides, a long non-coding RNA gene, PVT-1. Prior studies indicates that PVT-1 has pro-oncogenic properties however the function of PVT-1 in osteosarcoma is not well characterized. Methods: To understand PVT-1 copy number, Fluorescent In Situ Hybridization was performed on both osteosarcoma cell lines and osteosarcoma patient-derived xenografts. In addition the PVT-1 RNA level is elevated in a majority of osteosarcoma samples compared to normal bone. To test PVT-1 pro-oncogenic role in osteosarcoma, several functional assays were performed. Results: Our studies demonstrated that overexpression of PVT-1 in osteosarcoma cell lines promotes multiple tumorigenic behaviors including enhanced proliferation, migration, invasion and chemotherapeutic resistance to cisplatin. PVT-1’s ability to mediate metastasis and contribute to chemotherapeutic sensitivity is a shared phenotype of cancer stem cells. Based on this observation, we hypothesize targeting PVT-1 will reduce cancer stem-cell properties. Osteosarcoma lines with increased levels of PVT-1 exhibited higher expression of cancer stem cell genes: Nanog, SOX2, c-Myc, and Oct4 at both the transcriptomic and proteomic level. In Vitro and In Vivo self-renewal capacity studies showed enhanced osteosarcoma cell self-renewal in the PVT-1 overexpression cohort. Additional molecular studies were performed in order to gain additional insights into potential mechanism of action for PVT-1 including Reverse Phase Protein Array. Initial analysis suggest a role for PVT-1 in regulating the PI3K-AKT-TSC2 pathway. Conclusions: This suggests a potential oncogenic pathway in which PVT-1 enhances cancer stem cell phenotypes. On-going investigations are addressing potential PI3K/TSC2 pathway inhibitors, BEZ-2335 and LY3023414, which could be utilized to regulate PVT-1 mediated tumorigenic roles and cancer stem-like properties.