Global kinome silencing combined with 3D invasion screening of the tumor microenvironment identifies fibroblast-expressed PIK3Cδ involvement in triple-negative breast cancer progression

Gagliano, T.; Shah, K.; Gargani, S.; Lao, L.; Alsaleem, M.; Chen, J.; Ntafis, V.; Huang, P.; Ditsiou, A.; Vella, V.; Yadav, K.; Bienkowska, K.; Bresciani, G.; Kang, K.; Li, L.; Carter, P.; Benstead-Hum, G.; O'Hanlon, T.; Dean, M.; Pearl, F. M. G.; Lee, S.-C.; Rakha, E. A.; Green, A. R.; Kontoyiannis, D. L.; Song, E.; Stebbing, J.; Giamas, G.

doi:10.1101/822049

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bioRxiv · 10.1101/822049

Global kinome silencing combined with 3D invasion screening of the tumor microenvironment identifies fibroblast-expressed PIK3Cδ involvement in triple-negative breast cancer progression

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Abstract

As there is growing evidence for the tumor microenvironments (TME) role in tumorigenesis, we sought to investigate the role of fibroblast-expressed kinases in triple negative breast cancer (TNBC). Using a high-throughput kinome screen combined with 3D invasion assays, we identified fibroblast-expressed PIK3C{delta} (f-PIK3C{delta}) as a key regulator of progression. Although PIK3C{delta} has been mainly described in leucocytes, we detected high expression in primary fibroblasts derived from TNBC patients, while PIK3C{delta} was undetectable in cancer epithelial cell lines. Genetic and pharmacologic gain- and loss-of functions experiments verified the contribution of f-PIK3C{delta} in TNBC cell invasion. By employing an integrated secretomics and transcriptomics analysis, we revealed a paracrine mechanism via which f-PIK3C{delta} confers its pro-tumorigenic effects. Inhibition of f-PIK3C{delta} promoted the secretion of factors, including PLGF and BDNF, which subsequently led to upregulation of NR4A1 in TNBC cells where it acts as a tumor suppressor. Inhibition of PIK3C{delta} in an orthotopic BC mouse model reduced tumor growth only after inoculation with fibroblasts, indicating a role of f-PIK3C{delta} in cancer progression. Similar results were observed in the MMTV-PyMT transgenic BC mouse model, in addition to a decrease on tumor metastasis emphasizing the potential immune-independent effects of PIK3C{delta} inhibition. Finally, analysis of BC patient cohorts and TCGA datasets identified f-PIK3C{delta} (protein and mRNA levels) as an independent prognostic factor for overall and disease free survival, highlighting it as a therapeutic target for TNBC.

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Gagliano, T., Shah, K., Gargani, S., Lao, L., Alsaleem, M., Chen, J., Ntafis, V., Huang, P., Ditsiou, A., Vella, V., Yadav, K., Bienkowska, K., Bresciani, G., Kang, K., Li, L., Carter, P., Benstead-Hum, G., O'Hanlon, T., Dean, M., Pearl, F. M. G., Lee, S.-C., Rakha, E. A., Green, A. R., Kontoyiannis, D. L., Song, E., Stebbing, J., Giamas, G.. 2019-11-02. Global kinome silencing combined with 3D invasion screening of the tumor microenvironment identifies fibroblast-expressed PIK3Cδ involvement in triple-negative breast cancer progression. https://doi.org/10.1101/822049

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