a-method-for-screening-validation-resistant-mutations-against-kinase

A Method for Screening and Validation of Resistant Mutations Against Kinase Inhibitors

The discovery of BCR/ABL as a driver oncogene in chronic myeloid leukemia (CML) resulted in the development of Imatinib, which, in fact, demonstrated the ...

methods-for-evaluating-role-c-fos-dusp1-oncogene

Methods for Evaluating the Role of c-Fos and Dusp1 in Oncogene Dependence

The demonstration of tyrosine kinase inhibitors (TKIs) in treating chronic myeloid leukemia (CML) has heralded a new era in cancer therapeutics. However, ...

Cincinnati Children's Hospital Medical Center

Emergence of genetic resistance against kinase inhibitors poses a great challenge for durable therapeutic response. Here, we report a novel mechanism of JAK2 kinase inhibition by fedratinib (TG101348) that prevents emergence of genetic resistance. Using in vitro drug screening, we identified 211 amino-acid substitutions conferring resistance to ruxolitinib (INCB018424) and cross-resistance to the JAK2 inhibitors AZD1480, CYT-387 and lestaurtinib. In contrast, these resistant variants were fully sensitive to fedratinib. Structural modeling, coupled with mutagenesis and biochemical studies, revealed dual binding sites for fedratinib. In vitro binding assays using purified proteins showed strong affinity for the substrate-binding site (Kd = 20 nM) while affinity for the ATP site was poor (Kd = ~8 μM). Our studies demonstrate that mutations affecting the substrate-binding pocket encode a catalytically incompetent kinase, thereby preventing emergence of resistant variants. Most importantly, our data suggest that in order to develop resistance-free kinase inhibitors, the next-generation drug design should target the substrate-binding site. 

Targeting substrate-site in Jak2 kinase prevents emergence of genetic resistance.

Tyrosine-kinase inhibitor (TKI) therapy for human cancers is not curative, and relapse occurs owing to the continued presence of tumor cells, referred to as minimal residual disease (MRD). The survival of MRD stem or progenitor cells in the absence of oncogenic kinase signaling, a phenomenon referred to as intrinsic resistance, depends on diverse growth factors. Here we report that oncogenic kinase and growth-factor signaling converge to induce the expression of the signaling proteins FBJ osteosarcoma oncogene (c-FOS, encoded by Fos) and dual-specificity phosphatase 1 (DUSP1). Genetic deletion of Fos and Dusp1 suppressed tumor growth in a BCR-ABL fusion protein kinase-induced mouse model of chronic myeloid leukemia (CML). Pharmacological inhibition of c-FOS, DUSP1 and BCR-ABL eradicated MRD in multiple in vivo models, as well as in mice xenotransplanted with patient-derived primary CML cells. Growth-factor signaling also conferred TKI resistance and induced FOS and DUSP1 expression in tumor cells modeling other types of kinase-driven leukemias. Our data demonstrate that c-FOS and DUSP1 expression levels determine the threshold of TKI efficacy, such that growth-factor-induced expression of c-FOS and DUSP1 confers intrinsic resistance to TKI therapy in a wide-ranging set of leukemias, and might represent a unifying Achilles' heel of kinase-driven cancers.

Zachary Kincaid

Divisions of Experimental Hematology and Cancer Pathology,
Cancer Blood Disease Institute,
Divisions of Experimental Hematology and Cancer Pathology, Cancer Blood Disease Institute,
Cancer Blood Disease Institute, Divisions of Experimental Hematology and Cancer Pathology

Cincinnati Children's Hospital Medical Center

A Method for Screening and Validation of Resistant Mutations Against Kinase Inhibitors

Methods for Evaluating the Role of c-Fos and Dusp1 in Oncogene Dependence

Zachary Kincaid

Divisions of Experimental Hematology and Cancer Pathology,Cancer Blood Disease Institute,Divisions of Experimental Hematology and Cancer Pathology, Cancer Blood Disease Institute,Cancer Blood Disease Institute, Divisions of Experimental Hematology and Cancer Pathology

Cincinnati Children's Hospital Medical Center

A Method for Screening and Validation of Resistant Mutations Against Kinase Inhibitors

Methods for Evaluating the Role of c-Fos and Dusp1 in Oncogene Dependence

Divisions of Experimental Hematology and Cancer Pathology,
Cancer Blood Disease Institute,
Divisions of Experimental Hematology and Cancer Pathology, Cancer Blood Disease Institute,
Cancer Blood Disease Institute, Divisions of Experimental Hematology and Cancer Pathology