Cell line-derived xenografts (CDXs) are an integral part of drug efficacy testing during development of new pharmaceuticals against cancer but their accuracy in predicting clinical responses in patients have been debated. Patient-derived xenografts (PDXs) are thought to be more useful for predictive biomarker identification for targeted therapies, including in metastatic melanoma, due to their similarities to human disease. Here, tumor biopsies from fifteen patients and ten widely-used melanoma cell lines were transplanted into immunocompromised mice to generate PDXs and CDXs, respectively. Gene expression profiles generated from the tumors of these PDXs and CDXs clustered into distinct groups, despite similar mutational signatures. Hypoxia-induced gene signatures and overexpression of the hypoxia-regulated miRNA hsa-miR-210 characterized CDXs. Inhibition of hsa-miR-210 with decoys had little phenotypic effect in vitro but reduced sensitivity to MEK1/2 inhibition in vivo, suggesting down-regulation of this miRNA could result in development of resistance to MEK inhibitors.

Cell line-derived xenografts (CDXs) are an integral part of drug efficacy testing during development of new pharmaceuticals against cancer but their accuracy in predicting clinical responses in patients have been debated. Patient-derived xenografts (PDXs) are thought to be more useful for predictive biomarker identification for targeted therapies, including metastatic melanoma, due to their similarities to human disease. Here, tumor biopsies from patients and ten widely-used melanoma cell lines were transplanted into immunocompromised mice to generate PDXs and CDXs, respectively. Gene expression profiles generated from the tumors of these PDXs and CDXs clustered into distinct groups, despite similar mutational signatures. Hypoxia-induced gene signatures and overexpression of the hypoxia-regulated miRNA hsa-miR-210 characterized CDXs. Inhibition of hsa-miR-210 with decoys had little phenotypic effect in vitro but resulted in reduced sensitivity to MEK1/2 inhibition in vivo, suggesting down-regulation of this miRNA could result in development of resistance to MEK inhibitors. Citation Format: Joydeep Bhadury, Berglind O. Einarsdottir, Agnieszka Podraza, Roger Olofsson Bagge, Ulrika Stierner, Lars Ny, Marcela Dávila López, Jonas A. Nilsson. Hypoxia-regulated gene expression explains differences between cell line-derived xenografts and patient-derived xenografts. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 642.

protein SUMMARY STATEMENTSensitizing tumors to cisplatin would be of considerable therapeutic benefit. Here we show a novel mechanism of cisplatin sensitization via oxidation of ASNA-1 in a Caenorhabditis elegans model. ABSTRACTCisplatin is a frontline cancer treatment, but intrinsic or acquired resistance is common. We previously showed that ASNA-1/TRC40 inactivation increases cisplatin sensitivity in mammalian cells and a Caenorhabditis elegans asna-1 knockdown model. ASNA-1 has conserved tail-anchored protein (TAP) targeting and insulin secretion functions. Here we examined the mechanism of ASNA-1 action. We show that ASNA-1 exists in two physiologically-responsive redox states with separable TAP-targeting and insulin secretion functions. Cisplatin-generated ROS targeted ASNA-1 oxidation, resulting in a selective targeting defect of an ASNA-1-dependent TAP. Increased ASNA-1 oxidation sensitized worms to cisplatin cytotoxicity. Mutants with a redox balance favoring oxidized ASNA-1 were cisplatin sensitive as null mutants by diverting ASNA-1 away from its TAP-targeting role and 2 instead perturbing endoplasmic reticulum (ER) function. Mutations in the ASNA-1 receptor required for TAP insertion induced equivalent cisplatin sensitivity. We reveal a previously undescribed cellular dysfunction induced by cisplatin, identify a cisplatin target, and show that drug exposure causes TAP targeting-induced ER dysfunction. Therapeutic oxidation of ASNA-1 could be a clinically useful means to increase cisplatin sensitivity, reduce cytotoxic drug doses, and counteract cisplatin resistance. AUTHOR SUMMARYCisplatin is a very effective anti-cancer drug and is widely used as a frontline treatment.However, tumor resistance limits its use. Tumor re-sensitization would improve cancer treatment. ASNA-1/TRC40 knockdown in Caenorhabditis elegans and mammals results in cisplatin hypersensitivity, but the underlying mechanistic details are largely unknown. We show that in C. elegans ASNA-1 mutants, increased cisplatin killing is coupled with delocalization of a tail-anchored protein, SEC-61b, a membrane protein that should reach the ER and is instead mistargeted. Like its homologs, the reduced form of worm ASNA-1 is needed for targeting activity. Targeting is blocked upon ASNA-1 oxidation after cisplatin treatment, likely via reactive oxygen species (ROS) generated by cisplatin treatment. Nevertheless, the oxidized form of the protein can execute other functions like insulin secretion. We show also that mutants with high oxidized ASNA-1 levels are cisplatin sensitive. Additionally, cisplatin induced mistargeting strictly acts through ASNA-1 inactivation. Thus, we define a pathway from cisplatin exposure that targets protein (ASNA-1) inactivation, consequently leading to mis-targeting of proteins that need ASNA-1 for their maturation. This multi-step process provides vital information about likely proteins that can be targeted by drugs to enhance cisplatin mediated killing and improve chemotherapy.