Rhabdomyosarcoma (RMS) is a devastating pediatric soft tissue cancer. Currently, the standard treatment regimen for RMS patients remains relatively unchanged. Conventional treatment of RMS includes a combination of chemotherapy, radiation, and surgical tumor resection. Unfortunately, with the heterogeneity of cancer between patients, these therapies are not always effective and can cause undesired health issues for the patient due to their non-specific effects. Targeted drug therapy can help patients live more normal lives. The angiotensin II receptor type 1 (AGTR1) and 2 (AGTR2) are potential targeted therapy targets that can inhibit RMS cancer growth and cause less side effects compared to conventional therapies. AGTR1/2 are the main effectors in the renin angiotensin system regulating cardiovascular health. While there are Federal Drug Administration (FDA) drugs blocking these receptors to treat high blood pressure (Irbesartan), AGTR1 and AGTR2 have yet to be investigated for their role in RMS. Tumor propagating cells (TPC), which function as tumor stem cells in RMS, are proposed to drive tumor metastasis and relapse through a process called self-renewal. Preliminary disruption of AGTR1 and AGTR2 in the two major subtypes of RMS (embryonal and alveolar) with the CRISPR/Cas9 gene editing system resulted in decreased tumor cell growth and self-renewal capabilities. RMS cell lines treated with Irbesartan also decreased in viability compared to untreated cells. Based on our preliminary results, I propose that AGTR1/2 plays a role in regulating RMS cell growth and self-renewal. Further functional characterization of AGTR1/2 and investigation of the cellular mechanism by which AGTR1/2 regulates RMS tumor cell growth and self-renewal can provide a strong rationale for prioritizing AGTR1/2 as targets for drug therapies to slow the progression of RMS without greatly compromising more of the patient's health.

Embryonal rhabdomyosarcoma (ERMS) is a common pediatric cancer that has poor prognosis for patients with relapsed disease. ERMS typically harbors mutations in one of 3 RAS proteins. Mutations in NRAS, a member of the RAS family, have been shown to be a driver for many different cancers, including ERMS. The Chen lab previously demonstrated that genetic disruption of the NRAS gene by the CRISPR/Cas9 technique successfully reduced ERMS tumor growth in a human xenograft mouse model. However, these mice also experienced disease relapse. I was able to confirm successful targeting of at least one copy of NRAS in ERMS cells. I have subsequently isolated clones of ERMS cells that continued to grow despite the presence of NRAS gene disruption. In my investigation of candidate genes and pathways that might be responsible for driving continued ERMS tumor cell growth, I saw an increase in the level of YAP1 being produced in NRAS-targeted ERMS cells when compared to the control cells. Based on my preliminary findings, once NRAS is successfully disrupted in ERMS cells, tumor relapse is then driven instead by YAP1. This study could provide novel insight into the mechanisms underlying cancer relapse in response to NRAS targeting and promise alternative treatment plans for ERMS patients.