Resistance to Src inhibition alters the BRAF-mutant tumor secretome to promote an invasive phenotype and therapeutic escape through a FAK>p130Cas>c-Jun signaling axis

Abstract

Few therapy options exist for patients with advanced papillary and anaplastic thyroid cancer. We and others have previously identified c-Src as a key mediator of thyroid cancer pro-tumorigenic processes and a promising therapeutic target for thyroid cancer. To increase the efficacy of targeting Src in the clinic, we sought to define mechanisms of resistance to the Src inhibitor, dasatinib, to identify key pathways to target in combination. Using a panel of thyroid cancer cell lines expressing clinically relevant mutations in BRAF or RAS , which were previously developed to be resistant to dasatinib, we identified a switch to a more invasive phenotype in the BRAF -mutant cells as a potential therapy escape mechanism. This phenotype switch is driven by FAK kinase activity, and signaling through the p130Cas>c-Jun signaling axis. We have further shown this more invasive phenotype is accompanied by alterations in the secretome through the increased expression of pro-inflammatory cytokines, including IL-1β, and the pro-invasive metalloprotease, MMP-9. Furthermore, IL-1β signals via a feedforward autocrine loop to promote invasion through a FAK>p130Cas>c-Jun>MMP-9 signaling axis. We further demonstrate that upfront combined inhibition of FAK and Src synergistically inhibits growth and invasion, and induces apoptosis in a panel of BRAF- and RAS- mutant thyroid cancer cell lines. Together our data demonstrate that acquired resistance to single-agent Src inhibition promotes a more invasive phenotype through an IL-1β>FAK>p130Cas>c-Jun>MMP signaling axis, and that combined inhibition of FAK and Src has the potential to block this inhibitor-induced phenotype switch.

Methylglyoxal Acts as a Tumor-Promoting Factor in Anaplastic Thyroid Cancer

“…Experimental and epidemiological studies revealed that chronic inflammation is a feature of ATC [44,45,46]. In particular, ATC shows increased expression of several proinflammatory cytokines (especially of IL-1β) that, via a feedforward autocrine loop, promotes cell invasion in this cancer type [46]. In order to also verify the physiological relevance of IL-1β in our in vitro cell models, we firstly investigated IL-1β secretion and signaling in ATC CAL62 and 8505C cells as well as in PTC B-CPAP and TPC1 cells for comparison.…”

“…Thus, we identified a novel mechanism in TGF-β1 signaling [43]. FAK is a critical substrate that regulates several cellular events including migration and invasion through its dual function as a kinase and scaffolding protein [46]. FAK autophosphorylation leads to the recruitment of Src, and this complex signals to downstream effectors, including pro-invasive genes, such as MMPs [46].…”

“…FAK is a critical substrate that regulates several cellular events including migration and invasion through its dual function as a kinase and scaffolding protein [46]. FAK autophosphorylation leads to the recruitment of Src, and this complex signals to downstream effectors, including pro-invasive genes, such as MMPs [46]. We observed that MMP1 expression levels increased in ATC cells to promote invasion, suggesting the involvement of this MMP in sustaining the aggressive phenotype of ATC, which was in agreement with a similar role for another MMP (MMP9) in the same malignancy [46].…”

BCAR1 promotes proliferation and cell growth in lung adenocarcinoma via upregulation of POLR2A

“…POLR2A was pulled down by BCAR1 in 293T cells, probably due to tissue-specific or tumor-specific interactions between these two proteins. However, the BCAR1/c-JUN cascade has been shown to upregulate the expression of BRAF, 40 which is believed to be an upstream regulator of POLR2A. 41 Based on these findings, we speculate that BCAR1 can, at the very least, indirectly upregulate POLR2A expression, which has critical biological functions leading to cell proliferation, cell growth, and subsequent poor prognosis in lung cancer cases (Fig 4).…”

Engineering Multidimensional Evolutionary Forces to Combat Cancer

“…Autoinducers and their receptors are important targets for disrupting pathogenic processes and an active area of research (74). The corollary in cancer is the secretion of factors by therapeutically stressed tumor cells or the microenvironment that can support tumor cell survival (75)(76)(77).…”