Standard treatment for sarcoma is surgery and chemotherapy. Drug treatment usually includes a combination of doxorubicin and ifosfamide. Unfortunately, the efficacy of these agents is hampered by the eventual development of multidrug resistance (MDR). The mechanism of acquiring MDR in sarcomas is not well understood. Experimental evidence from several laboratories implicate a wide range of mechanisms including miRs (also known as miRNAs) that contribute to drug sensitivity/resistance and reversing MDR has been a high priority goal for clinical and investigational oncologists.
miRs are non-coding RNA chains of 21-25 nucleotides. The miRs are important regulators of gene and protein expressions; controlling many cellular functions such as cell proliferation/differentiation, apoptosis, oncogenesis and drug sensitivity in tumor cells. As a consequence of the aberrantly expressed miRs playing key roles in the development of human cancer and the mechanisms of chemotherapy drug resistance, correcting these miR deregulation and deficiencies by either antagonizing or restoring miR function may provide a significant therapeutic benefit for cancer treatment.
The central hypothesis of this proposal is based on the observation that the therapeutically useful miR-15b is expressed at very low levels in drug-resistant osteosarcoma cells KHOSR2 and U-2OSMR, but is highly expressed in drug sensitive counterparts. Re-introduction of miR-15 by transfection suppresses Wee 1 expression and reverses doxorubicin resistance in KHOSR2 and U-2OSMR cells, suggesting that restoration of miR-15b expression is a promising anti-osteosarcoma strategy in reverse drug resistance. The hypothesis has been formulated based on preliminary data produced in our laboratory.
The hypothesis will be tested with three specific aims: (1) Determine the relative expression levels of miR-15b and Wee 1 in osteosarcoma tissue samples and correlate them to clinical outcome; (2) Comprehensively catalogue all of the genes in drug resistant osteosarcoma cell lines whose expression levels are affected by miR-15b; (3) Evaluate the effect of miR-15b delivery with respect to reversing drug resistance in a xenograft mouse model of osteosarcoma. The research provides new, potentially robust approaches to treat patients with drug resistant osteosarcoma. Ultimately, such knowledge has the potential to improve care for patients with other cancers as well.