Src family kinases differentially influence glioma growth and motility

Abstract

Src-family kinase (SFK) signaling impacts multiple tumor-related properties, particularly in the context of the brain tumor glioblastoma. Consequently, the pan-SFK inhibitor dasatinib has emerged as a therapeutic strategy, despite physiologic limitations to its effectiveness in the brain. We investigated the importance of individual SFKs (Src, Fyn, Yes, and Lyn) to glioma tumor biology by knocking down individual SFK expression both in culture (LN229, SF767, GBM8) and orthotopic xenograft (GBM8) contexts. We evaluated the effects of these knockdowns on tumor cell proliferation, migration, and motility-related signaling in culture, as well as overall survival in the orthotopic xenograft model. The four SFKs differed significantly in their importance to these properties. In culture, Src, Fyn, and Yes knockdown generally reduced growth and migration and altered motility-related phosphorylation patterns while Lyn knockdown did so to a lesser extent. However the details of these effects varied significantly depending on the cell line: in no case were conclusions about the role of a particular SFK applicable to all of the measures or all of the cell types examined. In the orthotopic xenograft model, mice implanted with non-target or Src or Fyn knockdown cells showed no differences in survival. In contrast, mice implanted with Yes knockdown cells had longer survival, associated with reduced tumor cell proliferation. Those implanted with Lyn knockdown cells had shorter survival, associated with higher overall tumor burden. Together, our results suggest that Yes signaling directly affects tumor cell biology in a pro-tumorigenic manner, while Lyn signaling affects interactions between tumor cells and the microenvironment in an anti-tumor manner. In the context of therapeutic targeting of SFKs, these results suggest that pan-SFK inhibitors may not produce the intended therapeutic benefit when Lyn is present.

A phase 1 and randomized, placebo‐controlled phase 2 trial of bevacizumab plus dasatinib in patients with recurrent glioblastoma: Alliance/North Central Cancer Treatment Group N0872

“…36 The lack of a clinical benefit was considered to be a potential result of the different molecular profiles of dasatinib targets between archival tumor resected at the time of the diagnosis of GBM and the profile at disease recurrence; it also was noted that response to dasatinib in patients with GBM may require driver mutations in dasatinib targets. 37 Consistent with this, higher levels of LYN expression were correlated with both a PFS6 and OS advantage in the current study, regardless of treatment. The results indicate that individual SFKs (Src, Fyn, YES, and LYN) differ significantly with regard to their importance for glioma growth and motility, and the efficacy of dasatinib therapy may depend on the relative expression of particular SFKs.…”

“…35 Recent clinical research investigating dasatinib monotherapy in patients with recurrent GBM reported a PFS6 of only 6%, despite efforts to enrich the patient population and to increase the dose of dasatinib, however. 37 It is interesting to note that depletion of LYN resulted in increased tumor growth and reduced OS in these orthotopic, patientderived GBM xenografts, suggesting a tumor suppressor function for LYN in GBM. The strategy of targeting SFK signaling has been studied recently in culture and orthotopic xenograft models.…”

“…The results indicate that individual SFKs (Src, Fyn, YES, and LYN) differ significantly with regard to their importance for glioma growth and motility, and the efficacy of dasatinib therapy may depend on the relative expression of particular SFKs. 37 It is interesting to note that depletion of LYN resulted in increased tumor growth and reduced OS in these orthotopic, patientderived GBM xenografts, suggesting a tumor suppressor function for LYN in GBM. 37 Consistent with this, higher levels of LYN expression were correlated with both a PFS6 and OS advantage in the current study, regardless of treatment.…”

“…37 It is interesting to note that depletion of LYN resulted in increased tumor growth and reduced OS in these orthotopic, patientderived GBM xenografts, suggesting a tumor suppressor function for LYN in GBM. 37 Consistent with this, higher levels of LYN expression were correlated with both a PFS6 and OS advantage in the current study, regardless of treatment. Conversely, a high level of pSRC correlated with a PFS6 disadvantage, regardless of treatment, suggesting that the increased activation of SFKs contributes to the aggressive nature of GBM.…”

FYN tyrosine kinase, a downstream target of receptor tyrosine kinases, modulates anti-glioma immune responses

“…Several in-vitro studies showed that FYN knockdown is associated with decreased cell migration and proliferation of glioma cells 3,8,9 . Nevertheless, in vivo human glioma xenograft models of FYN Knockdown in immune-suppressed animals failed to show any difference in survival 8 . Therefore, an immune-competent mouse model that enables the generation of FYN knockdown gliomas amenable for understanding the mechanism of anti-glioma immune response is essential.…”