REDD1 is a determinant of the sensitivity of renal cell carcinoma cells to autophagy inhibition that can be therapeutically exploited by targeting PIM kinase activity
Abstract
Purpose
Repurposing FDA approved drugs with off-target autophagy inhibition such as chloroquine/hydroxychloroquine (CQ, HCQ) has produced modest anticancer activity in clinical trials, due in part, to a failure to define predictive biomarkers that enable the selection of patients that best respond to this treatment strategy. We identified a new role for REDD1 as a determinant of sensitivity to autophagy inhibition in renal cell carcinoma (RCC).
Experimental Design
RNA sequencing, qRT-PCR, immunoblotting, gene silencing, knockout and overexpression studies revealed that REDD1 expression is a key regulator of cell death stimulated by autophagy inhibitors. Comprehensivein vitroandin vivostudies were conducted to evaluate the selectivity, tolerability, and efficacy of the PIM kinase inhibitor TP-3654 and CQ in preclinical models of renal cell carcinoma (RCC). Markers of autophagy inhibition and cell death were evaluated in tumor specimens.
Results
Transcriptomic analyses identified REDD1 (DDIT4) as a highly induced gene in RCC cells treated with the PIM kinase inhibitor TP-3654. Focused studies confirmed that PIM1 inhibition was sufficient to induce REDD1 and stimulate autophagy through the AMPK cascade.DDIT4knockout and overexpression studies established its mechanistic role as a regulator of sensitivity to autophagy inhibition. Inhibition of autophagy with CQ synergistically enhanced the in vitroandin vivoanticancer activity of TP-3654.
Conclusions
Our findings identify REDD1 as a novel determinant of the sensitivity of RCC cells to autophagy inhibition and support further investigation of PIM kinase inhibition as a precision strategy to drive sensitivity to autophagy-targeted therapies through REDD1 upregulation.
Translational Relevance
PIM kinases are overexpressed in renal cell carcinoma (RCC) and other malignancies. Here we show that targeting PIM1 significantly upregulates REDD1/DDIT4expression, resulting in inhibition of mTOR and autophagy activation. REDD1 induction was determined to be a major factor that regulates the sensitivity of RCC cells to autophagy inhibition. Comprehensivein vitroandin vivostudies in preclinical models of RCC demonstrated that the PIM kinase inhibitor TP-3654 induced REDD1-mediated autophagy and synergistically sensitized cells to autophagy inhibition. Our findings define a new role for REDD1 as a determinant of the sensitivity of RCC cells to autophagy inhibition and demonstrate that antagonizing PIM kinase activity is a precision approach to augment REDD1 levels and potentiate the therapeutic benefit of targeting the autophagy pathway.
Related articles
Related articles are currently not available for this article.