piperidines and Oncogene-Addiction

Chromosome instability (CIN) has been associated with therapeutic resistance in many cancers. However, whether tumours become genomically unstable as an evolutionary mechanism to overcome the bottleneck exerted by therapy is not clear. Using a CIN model of Kras-driven breast cancer, we demonstrate that aneuploid tumours acquire genetic modifications that facilitate the development of resistance to targeted therapy faster than euploid tumours. We further show that the few initially chromosomally stable cancers that manage to persist during treatment do so concomitantly with the acquisition of CIN. Whole-genome sequencing analysis revealed that the most predominant genetic alteration in resistant tumours, originated from either euploid or aneuploid primary tumours, was an amplification on chromosome 6 containing the cMet oncogene. We further show that these tumours are dependent on cMet since its pharmacological inhibition leads to reduced growth and increased cell death. Our results highlight that irrespective of the initial CIN levels, cancer genomes are dynamic and the acquisition of a certain level of CIN, either induced or spontaneous, is a mechanism to circumvent oncogene addiction.

Topics: Aneuploidy; Animals; Breast Neoplasms; Chromosomal Instability; Drug Resistance, Neoplasm; Female; Mice; Mice, Transgenic; Neoplasms, Experimental; Oncogene Addiction; Piperidines; Pyridazines; Pyrimidines

Metastatic medullary thyroid cancer (MTC) is incurable and FDA-approved kinase inhibitors that include oncogenic RET as a target do not result in complete responses. Association studies of human MTCs and murine models suggest that the CDK/RB pathway may be an alternative target. The objective of this study was to determine if CDKs represent therapeutic targets for MTC and to define mechanisms of activity. Using human MTC cells that are either sensitive or resistant to vandetanib, we demonstrate that palbociclib (CDK4/6 inhibitor) is not cytotoxic to MTC cells but that they are highly sensitive to dinaciclib (CDK1/2/5/9 inhibitor) accompanied by reduced CDK9 and RET protein and mRNA levels. CDK9 protein was highly expressed in 83 of 83 human MTCs and array-comparative genomic hybridization had copy number gain in 11 of 30 tumors. RNA sequencing demonstrated that RNA polymerase II-dependent transcription was markedly reduced by dinaciclib. The CDK7 inhibitor THZ1 also demonstrated high potency and reduced RET and CDK9 levels. ChIP-sequencing using H3K27Ac antibody identified a superenhancer in intron 1 of RET. Finally, combined inhibition of dinaciclib with a RET kinase inhibitor was synergistic. In summary, we have identified what we believe is a novel mechanism of RET transcription regulation that potentially can be exploited to improve RET therapeutic targeting.

Topics: Antineoplastic Agents; Bridged Bicyclo Compounds, Heterocyclic; Carcinoma, Neuroendocrine; Cell Line, Tumor; Cyclic N-Oxides; Cyclin-Dependent Kinases; Drug Resistance, Neoplasm; Drug Synergism; Enhancer Elements, Genetic; Gene Expression Regulation, Neoplastic; Humans; Indolizines; Introns; Molecular Targeted Therapy; Oncogene Addiction; Piperazines; Piperidines; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-ret; Pyridines; Pyridinium Compounds; Quinazolines; Thyroid Gland; Thyroid Neoplasms; Tissue Array Analysis; Transcription, Genetic