Protein Tyrosine Phosphatase SHP2 Controls Interleukin-8 Expression in Breast Cancer Cells

Abstract

Treatment of metastasis remains a clinical challenge and the majority of breast cancer-related deaths are the result of drug-resistant metastases. The protein tyrosine phosphatase SHP2 encoded by the proto-oncogene PTPN11 promotes breast cancer progression. Inhibition of SHP2 has been shown to decrease metastases formation in various breast cancer models, but specific downstream effectors of SHP2 remain poorly characterized. Certain cytokines in the metastatic cascade facilitate local invasion and promote metastatic colonization. In this study, we investigated cytokines affected by SHP2 that could be relevant for its pro-tumorigenic properties. We used a cytokine array to investigate differentially released cytokines in the supernatant of SHP2 inhibitor-treated breast cancer cells. Expression of CXCL8 transcripts and protein abundance were assessed in human breast cancer cell lines in which we blocked SHP2 using shRNA constructs or an allosteric inhibitor. The impact of SHP2 inhibition on the phospho-tyrosine-proteome and signaling was determined using mass spectrometry. From previously published RNAseq data (Aceto et al. in Nat. Med. 18:529–37, 2012), we computed transcription factor activities using an integrated system for motif activity response analysis (ISMARA) (Balwierz et al. in Genome Res. 24:869–84, 2014). Finally, using siRNA against ETS1, we investigated whether ETS1 directly influences CXCL8 expression levels. We found that IL-8 is one of the most downregulated cytokines in cell supernatants upon SHP2 blockade, with a twofold decrease in CXCL8 transcripts and a fourfold decrease in IL-8 protein. These effects were also observed in preclinical tumor models. Analysis of the phospho-tyrosine-proteome revealed that several effectors of the mitogen-activated protein kinase (MAPK) pathway are downregulated upon SHP2 inhibition in vitro. MEK1/2 inhibition consistently reduced IL-8 levels in breast cancer cell supernatants. Computational analysis of RNAseq data from SHP2-depleted tumors revealed reduced activity of the transcription factor ETS1, a direct target of ERK and a transcription factor reported to regulate IL-8 expression. Our work reveals that SHP2 mediates breast cancer progression by enhancing the production and secretion of the pro-metastatic cytokine IL-8. We also provide mechanistic insights into the effects of SHP2 inhibition and its downstream repercussions. Overall, these results support a rationale for targeting SHP2 in breast cancer.

SHP2 inhibition displays efficacy as a monotherapy and in combination with JAK2 inhibition in preclinical models of myeloproliferative neoplasms

“…[63][64][65][77][78][79][80][81][82][83][84][85][86][87][88][89] The addition of RMC-4550 to ruxolitinib in our studies drove the levels of TNFα, which contributes to clonal expansion in MPN models, 63 below those detected after vehicle and ruxolitinib monotherapy. While BET inhibition antagonizes MPN associated inflammatory signals via suppression of NFκB activity, 73 SHP2 has been implicated in positively regulating signaling by IL-1β, [90][91][92] IL-6, 93,94 CXCL8/IL-8, 95,96 as well as IL-13, 97 which has recently been implicated in driving myelofibrosis in MPN models. 86 SHP2 can also promote NFκB activation and IL-6 production induced by IL-1 signaling 98 in fibroblasts, but we did not detect modulation of the phosphorylation of p65 in MPN model cell lines or in cells from our mouse model experiments (Figure S11).…”

Tyrosine phosphatase PTPN11/SHP2 in solid tumors - bull’s eye for targeted therapy?

“…A novel substance that suppresses SHP2 and cyclin-dependent kinase 4 (CDK4), downregulates pERK and pRb expression, and boosts immunological function has been shown in recent research to prevent the development of TNBC ( 130 ). ETS oncogene 1 (ETS1) activity is decreased in TNBC cell lines when SHP2 is inhibited because it blocks the MAPK signaling cascade, which in turn downregulates IL-8 production ( 131 ). In TNBC, SHP2 knockout cells reconstituted with a phosphatase-dead SHP2 mutant are unable to (re-)activate AKT and MAPK signaling upon treatment with BYL719, which makes them sensitive to PI3K inhibition ( 132 ).…”