KRAS mutated tumours represent a large fraction of human cancers, but the vast majority remains refractory to current clinical therapies. Thus, a deeper understanding of the molecular mechanisms triggered by KRAS oncogene may yield alternative therapeutic strategies. Here we report the identification of a common transcriptional signature across mutant KRAS cancers of distinct tissue origin that includes the transcription factor FOSL1. High FOSL1 expression identifies mutant KRAS lung and pancreatic cancer patients with the worst survival outcome. Furthermore, FOSL1 genetic inhibition is detrimental to both KRAS-driven tumour types. Mechanistically, FOSL1 links the KRAS oncogene to components of the mitotic machinery, a pathway previously postulated to function orthogonally to oncogenic KRAS. FOSL1 targets include AURKA, whose inhibition impairs viability of mutant KRAS cells. Lastly, combination of AURKA and MEK inhibitors induces a deleterious effect on mutant KRAS cells. Our findings unveil KRAS downstream effectors that provide opportunities to treat KRAS-driven cancers.
Purpose: We investigated the role of the collagen-binding receptor discoidin domain receptor-1 (DDR1) in the initiation and development of bone metastasis.Experimental Design: We conducted immunohistochemical analyses in a cohort of 83 lung cancer specimens and examined phosphorylation status in a panel of human lung cancer cell lines. Adhesion, chemotaxis, invasiveness, metalloproteolytic, osteoclastogenic, and apoptotic assays were conducted in DDR1-silenced cells. In vivo, metastatic osseous homing and colonization were assessed in a murine model of metastasis.Results: DDR1 was expressed in a panel of human lung cancer cell lines, and high DDR1 levels in human lung tumors were associated with poor survival. Knockdown (shDDR1) cells displayed unaltered growth kinetics in vitro and in vivo. In contrast, shDDR1 cells showed reduced invasiveness in collagen matrices and increased apoptosis in basal conditions and induced apoptosis in vitro. More importantly, conditioned media of DDR1-knockdown cells decreased osteoclastogenic activity in vitro. Consequently, in a model of tumor metastasis to bone, lack of DDR1 showed decreased metastatic activity associated with reduced tumor burden and osteolytic lesions. These effects were consistent with a substantial reduction in the number of cells reaching the bone compartment. Moreover, intratibial injection of shDDR1 cells significantly decreased bone tumor burden, suggesting impaired colonization ability that was highly dependent on the bone microenvironment.Conclusions: Disruption of DDR1 hampers tumor cell survival, leading to impaired early tumor-bone engagement during skeletal homing. Furthermore, inhibition of DDR1 crucially alters bone colonization. We suggest that DDR1 represents a novel therapeutic target involved in bone metastasis.
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