Crosstalk between Akt signaling and cold shock proteins in mediating invasive cell phenotypes

// Raphael Hohlfeld 1 , Sabine Brandt 1 , Anja Bernhardt 1 , Xenia Gorny 1 , Daniel Schindele 2 , Burkhard Jandrig 2 , Martin Schostak 2 , Berend Isermann 3 , Jonathan A. Lindquist 1 and Peter R. Mertens 1 1 Clinic of Nephrology and Hypertension, Diabetes and Endocrinology, Otto-von-Guericke University Magdeburg, Magdeburg, Germany 2 Clinic of Urology, Otto-von-Guericke-University Magdeburg, Magdeburg, Germany 3 Institute of Clinical Chemistry and Pathobiochemistry, Otto-von-Guericke University Magdeburg, Magdeburg, Germany Correspondence to: Peter R. Mertens, email: peter.mertens@med.ovgu.de Keywords: clear cell renal cell carcinoma; cold shock proteins; YB-1; DbpA; Akt1 Received: December 22, 2017      Accepted: February 25, 2018      Published: April 10, 2018 ABSTRACT Cold shock proteins are up-regulated by cellular stress and orchestrate inflammatory responses, cell proliferation, and differentiation. Enhanced cold shock protein expression promotes malignant cell transformation; up-regulation is detected in most cancers and associated with poor prognosis. Akt1, a serine/threonine kinase, is a potent oncogene, which activates pro-proliferative and anti-apoptotic signaling pathways, and phosphorylates the cold shock domain. Unexpectedly, chicken-YB-1 abrogates PI3K-Akt-dependent oncogenic cell transformation in embryonic fibroblasts. Here, we addressed the question whether chicken and human Y-box binding protein-1 (YB-1) act differently on cell transformation, and how a related protein, DNA-binding protein-A (DbpA) behaves in comparison. NIH3T3 cells were transduced with lentiviral vectors encoding for myristoylated (constitutive active) Akt1, YB-1, DbpA, or shRNA targeting YB-1 expression. Colony formation assays showed that human YB-1 acts similar to chicken on Akt-dependent cell transformation. This activity was not titratable. Given the correlation of nuclear YB-1 and upregulated DbpA expression in a series of clear cell renal cell carcinomas ( n = 40) the colony formation assay was extended to include ectopic DbpA expression. DbpA alone prominently induced cell transformation, which was enhanced when constitutive active Akt1 or concomitant YB-1 expression was present. Notably, co-expression of DbpA together with YB-1 abrogated the repressive effect on Akt1 signaling observed with YB-1 alone. Macroscopically, some colonies yielded a remarkable “invasive” phenotype. Thus, cold shock proteins may convey profound anti- and pro-oncogenic effects on Akt-dependent cell transformation. DbpA is able to overcome the anti-oncogenic effects seen with combined YB-1 and Akt signaling in an in vitro model of colonial growth.