Sarcoma
Andrew Tieniber, MD
General Surgery Resident
University of Pennsylvania
phialdelphia, Pennsylvania, United States
Disclosure: I do not have any relevant financial / non-financial relationships with any proprietary interests.
Gastrointestinal stromal tumor (GIST) is the most common human sarcoma and is typically driven by a single mutation in the KIT receptor. While highly effective, imatinib is not curative. We sought to define the molecular subsets of tumor cells in GIST to identify potential mechanisms of tumor cell persistence during imatinib therapy.
Methods: KitV558Δ/+ mice, which spontaneously develop an intestinal GIST, were treated with imatinib or vehicle for 1 week. Tumors were sorted for non-immune (CD45-) cells and submitted for single-cell RNA sequencing (ScRNAseq, n=3/group). An existing bulk RNA sequencing human GIST dataset was used to correlate gene expression with pathologic features.
Results:
Unsupervised clustering revealed 4 molecularly defined subsets of tumor cells which expressed the canonical markers of GIST including Kit and Ano1 (Dog1), and the transcription factor Etv1. Clusters 2 and 3 were enriched for genes associated with epithelial-mesenchymal transition and metastasis (NES >2.0, FDR< 0.01), suggesting increased malignant potential. After imatinib therapy, clusters 1 and 4 decreased by 30% and 41%, while clusters 2 and 3 increased by 44% and 29%, respectively. Subsets of GIST cells that increased in proportion following imatinib had greater expression of the transcription factor Hand1, the growth factor Mdk (midkine), and the proliferation marker Pcna (p< 0.0001), all of which increased following imatinib. In human GIST, Hand1 expression was associated with metastatic and imatinib-resistant tumors as well as higher mitotic rate (p< 0.05, n=75), suggesting downstream Hand1 targets are important in tumor progression. Human GIST Mdk expression was associated with metastatic tumors and higher mitotic rate (p< 0.05, n=75), which may provide independent growth signaling in the presence of imatinib.
Conclusions:
ScRNAseq analysis of GIST revealed molecularly defined subsets of tumor cells at baseline. Imatinib increased specific tumor subsets expressing genes associated with GIST progression, highlighting the need for novel therapeutic strategies to target these persisting clusters.