Omic characterization of DSRCT and establishing the role of fibroblasts

Desmoplastic small round cell tumor (DSRCT) is a rare, usually incurable, pediatric sarcoma that afflicts mostly young males. While the EWS-WT1 fusion protein (FP) is a hallmark of DSRCT, equally pervasive is the dense fibroblastic stroma intermeshed with nests of small round blue cells. Herein, we propose to determine if the tumor/stroma interaction promotes the oncogenic pathways that drive tumor growth and survival while interrogating if such interactions differ among the recently proposed DSRCT subsets. Though the androgen receptor (AR) has been hypothesized to contribute to DSRCT tumorigenesis, given the male predominance, our group was the first to assess how it promotes tumor growth. Importantly, using transcriptomic profiling, we identified three DSRCT subtypes – 1) AR-positive, 2) NE-positive, and 3) hybrid AR/NE – that may shift the paradigm in how we treat patients. Notably, the transcriptomic profiling identified a fibroblast population in DSRCT. Given that desmoplasia is a hallmark of DSRCT, we suspect that the fibroblasts are essential for tumor progression. The current proposal builds on these exciting discoveries. The objective of this proposed work is to characterize the tumor microenvironment of DSRCT with respect to the AR pathway and the relationship between fibroblasts and DSRCT. While transcriptomic profiling has given rich data, proteomic markers are more clinically relevant and accessible. Therefore, we will use proteomic profiling to validate the DSRCT subtypes on a larger cohort. In Aim 2, we will assess the relationship between fibroblasts and DSRCT through co-culture of DSRCT and fibroblasts. The theme of this work is ‘Omic characterization of sarcomas and definition of novel targets.’ The two aims are complementary and addresses important knowledge gaps: 1) the role of AR and NE subtypes and 2) the role of desmoplasia, specifically fibroblasts. Aim 1: Characterize the proteomic profile of the tumor microenvironment of DSRCT. We will use multiplex immunofluorescence to study the nine patients that were used to initially describe the DSRCT subtypes. If we observe the same proteomic profile predicted by the transcriptomic profiling, we will study the remaining sixty patients. Aim 2: Determine if fibroblasts enable a pro-tumorigenic environment for DSRCT. We will co-culture fibroblasts and DSRCT cells at different ratios and assess the effect on DSRCT growth. Next, we will study the effect of AR (enzalutamide) and PI3K/Akt/mTOR (alpelisib and temsirolimus) inhibitors on DSRCT growth in co-culture with fibroblasts. Significance: Our team will be the first to assess the proteomic profile of DSRCT with respect to AR, NE, and the stromal cells. By studying relationship of fibroblasts and DSRCT, we will be the first to assess how fibroblasts enable a DSRCT growth and affect drug efficacy. By addressing these aims, this proposal will generate new research directions for identifying novel targets in DSRCT.