Repurposed floxacins targeting RSK4 prevent chemoresistance and metastasis in lung and bladder cancer

Abstract

Lung and bladder cancers are mostly incurable because of the early development of drug resistance and metastatic dissemination. Hence, improved therapies that tackle these two processes are urgently needed to improve clinical outcome. We have identified RSK4 as a promoter of drug resistance and metastasis in lung and bladder cancer cells. Silencing this kinase, through either RNA interference or CRISPR, sensitized tumor cells to chemotherapy and hindered metastasis in vitro and in vivo in a tail vein injection model. Drug screening revealed several floxacin antibiotics as potent RSK4 activation inhibitors, and trovafloxacin reproduced all effects of RSK4 silencing in vitro and in/ex vivo using lung cancer xenograft and genetically engineered mouse models and bladder tumor explants. Through x-ray structure determination and Markov transient and Deuterium exchange analyses, we identified the allosteric binding site and revealed how this compound blocks RSK4 kinase activation through binding to an allosteric site and mimicking a kinase autoinhibitory mechanism involving the RSK4’s hydrophobic motif. Last, we show that patients undergoing chemotherapy and adhering to prophylactic levofloxacin in the large placebo-controlled randomized phase 3 SIGNIFICANT trial had significantly increased (P = 0.048) long-term overall survival times. Hence, we suggest that RSK4 inhibition may represent an effective therapeutic strategy for treating lung and bladder cancer.

Allosteric Hotspots in the Main Protease of SARS-CoV-2

“…This motivated our use of MT to reveal fast signal propagation which happens often along allosteric communication pathways. MT have been effective in predicting relevant sites in catalytic enzymes such as caspase-1 [61] and RSK4 [68] .…”

“…Our methodologies are based on concepts from graph theory and the propagation of perturbations on a protein graph. We have previously demonstrated the applications of B2B-prop and MT analyses for the identification of allosteric sites and communication pathways in a range of biological settings [61] , [63] , [64] , [68] and have been benchmarked on extensive databases [65] , [66] . Applying B2B-prop to the SARS-CoV-2 M pro revealed a hot region of connectivity at the dimer interface.…”

“…Our methods provide in depth insights into the global connectivity and have been used to propose putative allosteric sites on the main protease which could be combined with drug repurposing for approved and investigational drugs to target potential allosteric sites [27] , [68] . Although B2B-prop and MT are based on static structures, they can be readily applied to ensembles of structures obtained from solution nuclear magnetic resonance (NMR) or MD.…”

“…Crucially, MT analysis takes into account all possible pathways, not just the shortest or optimal paths — an important feature since allosteric communication is known to involve multiple paths across the protein [67] . MT analysis has been successful in identifying allosteric paths in caspase-1 [61] , as well as previously unknown allosteric inhibitor binding sites in p90 ribosomal s6 kinase 4 (RSK4) which complemented and helped guide experimental and clinical studies in drug repurposing for lung cancer [68] .…”

Epigenetic modification and BRAF gene mutation in thyroid carcinoma

“…However, in transparent cell kidney cancer, high expression of RSK4 leads to poor prognosis [ 76 ]. Targeted inhibition of RSK4 can prevent chemotherapy resistance and metastasis of lung and bladder cancer [ 77 ], thus showing that RSK4 may have a double-edged role in tumours. High expression of RSK4 can directly act on ERK or downstream signalling, thereby inhibiting the MAPK signalling pathway and inhibiting TC.…”