pci-32765 and olaparib

The deletion of 11q (del(11q)) invariably comprises ATM gene in chronic lymphocytic leukemia (CLL). Concomitant mutations in this gene in the remaining allele have been identified in 1/3 of CLL cases harboring del(11q), being the biallelic loss of ATM associated with adverse prognosis. Although the introduction of targeted BCR inhibition has significantly favored the outcomes of del(11q) patients, responses of patients harboring ATM functional loss through biallelic inactivation are unexplored, and the development of resistances to targeted therapies have been increasingly reported, urging the need to explore novel therapeutic approaches. Here, we generated isogenic CLL cell lines harboring del(11q) and ATM mutations through CRISPR/Cas9-based gene-editing. With these models, we uncovered a novel therapeutic vulnerability of del(11q)/ATM-mutated cells to dual BCR and PARP inhibition. Ex vivo studies in the presence of stromal stimulation on 38 CLL primary samples confirmed a synergistic action of the combination of olaparib and ibrutinib in del(11q)/ATM-mutated CLL patients. In addition, we showed that ibrutinib produced a homologous recombination repair impairment through RAD51 dysregulation, finding a synergistic link of both drugs in the DNA damage repair pathway. Our data provide a preclinical rationale for the use of this combination in CLL patients with this high-risk cytogenetic abnormality.

Topics: Adenine; Animals; Antineoplastic Combined Chemotherapy Protocols; Ataxia Telangiectasia Mutated Proteins; Cell Line, Tumor; Chromosome Deletion; Chromosomes, Human, Pair 11; CRISPR-Cas Systems; Drug Synergism; Humans; Leukemia, Lymphocytic, Chronic, B-Cell; Mice; Mutagenesis, Site-Directed; Mutation; Phthalazines; Piperazines; Piperidines; Poly (ADP-Ribose) Polymerase-1; Poly(ADP-ribose) Polymerase Inhibitors; Proto-Oncogene Proteins c-bcr; Pyrazoles; Pyrimidines; Xenograft Model Antitumor Assays

Mantle cell lymphoma (MCL) presents a therapeutic challenge. The B cell targeting agent, ibrutinib, is currently one of the most effective second-line therapies for MCL, but frequently leads to development of drug resistance, and short overall survival time upon relapse. Olaparib targets tumor cells with deficiencies in single-strand DNA break repair and thus may slow the development of genetic drug resistance. We found that the olaparib-ibrutinib combination significantly inhibits cell culture growth compared to either drug alone in two genetically distinct MCL cell lines. Moreover, these inhibitory effects are either additive or synergistic, depending on genetic background. Culture growth is inhibited due to increases in apoptosis, cell death, and cell cycle arrest, and the magnitude of each is cell line dependent. The additive and synergistic inhibition of this combination additionally supports a therapeutic strategy involving lower dosing of each drug to reduce potential side effects.

Topics: Adenine; Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; Cell Proliferation; Drug Resistance, Neoplasm; Drug Synergism; Humans; Lymphoma, Mantle-Cell; Phthalazines; Piperazines; Piperidines; Pyrazoles; Pyrimidines; Tumor Cells, Cultured