Introduction

Hemangiosarcomas (HSAs) are aggressive, highly metastatic cancers that form malignant vessels. This tumor is more prevalent in dogs than any other animals, and outcomes for affected dogs are generally unfavorable. Recurrent mutations in PIK3CA gene were observed in canine HSAs, and they appear to establish angiogenic programs. In this study, we hypothesize that PIK3CA mutations activating PI3K pathway contribute to the molecular programs that create the immune niche in canine HSA.

Methods

We first engineered canine HSA cells to induce PIK3CA H1047R mutations using CRISPR/Cas9, followed by clonal selection of mutant and wild-type (WT) cells. Then, we examined cell growth rate and expression of γH2AX, DNA damage marker in mutant and WT cells with treatment of PI3K-alpha selective inhibitor (BYL719) and pan-PI3K inhibitor (ZSTK474).

Results

Our results showed that BYL719 decreased cell proliferation of PIK3CA mutant cells by 40–50% at 10 µM compared with that of WT cells, while no significant difference was observed between mutant and WT cells treated with ZSTK474. Expression levels of γH2AX were increased in both mutant and WT cells with treatment of BYL719 and ZSTK474; however, the ratio of change in γH2AX expression was smaller in mutant cells than that in WT cells.

Conclusion

These data suggest that activation of PI3K pathway is essential for tumor cell growth and that PIK3CA mutation-induced pathways are targetable by PI3K-alpha selective inhibitor in canine HSA. Our ongoing work is to determine if canine HSA cells have cell-autonomous capacity to govern hematopoietic progenitors and immune cells, potentially establishing the tumor immune niche.

Funding Information

This work is supported by grant (#02759) from the AKC Canine Health Foundation and by the Animal Cancer Care and Research Program of the University of Minnesota.