Targeting BCR-ABL-Independent TKI Resistance in Chronic Myeloid Leukemia by mTOR and Autophagy Inhibition.

Background: Imatinib and second-generation tyrosine kinase inhibitors (TKIs) nilotinib and dasatinib have statistically significantly improved the life expectancy of chronic myeloid leukemia (CML) patients; however, resistance to TKIs remains a major clinical challenge. Although ponatinib, a third-generation TKI, improves outcomes for patients with BCR-ABL-dependent mechanisms of resistance, including the T315I mutation, a proportion of patients may have or develop BCR-ABL-independent resistance and fail ponatinib treatment. By modeling ponatinib resistance and testing samples from these CML patients, it is hoped that an alternative drug target can be identified and inhibited with a novel compound. Methods: Two CML cell lines with acquired BCR-ABL-independent resistance were generated following culture in ponatinib. RNA sequencing and gene ontology (GO) enrichment were used to detect aberrant transcriptional response in ponatinib-resistant cells. A validated oncogene drug library was used to identify US Food and Drug Administration-approved drugs with activity against TKI-resistant cells. Validation was performed using bone marrow (BM)-derived cells from TKI-resistant patients (n = 4) and a human xenograft mouse model (n = 4-6 mice per group). All statistical tests were two-sided. Results: We show that ponatinib-resistant CML cells can acquire BCR-ABL-independent resistance mediated through alternative activation of mTOR. Following transcriptomic analysis and drug screening, we highlight mTOR inhibition as an alternative therapeutic approach in TKI-resistant CML cells. Additionally, we show that catalytic mTOR inhibitors induce autophagy and demonstrate that genetic or pharmacological inhibition of autophagy sensitizes ponatinib-resistant CML cells to death induced by mTOR inhibition in vitro (% number of colonies of control[SD], NVP-BEZ235 vs NVP-BEZ235+HCQ: 45.0[17.9]% vs 24.0[8.4]%, P = .002) and in vivo (median survival of NVP-BEZ235- vs NVP-BEZ235+HCQ-treated mice: 38.5 days vs 47.0 days, P = .04). Conclusion: Combined mTOR and autophagy inhibition may provide an attractive approach to target BCR-ABL-independent mechanism of resistance.

Axl Blockade by BGB324 Inhibits BCR-ABL Tyrosine Kinase Inhibitor-Sensitive and -Resistant Chronic Myeloid Leukemia.

Purpose: BCR-ABL kinase inhibitors are employed successfully for chronic myeloid leukemia (CML) treatment. However, resistant disease and persistence of BCR-ABL1-independent leukemia stem and progenitor cells (LSPC) remain clinical challenges. The receptor tyrosine kinase Axl can mediate survival and therapy resistance of different cancer cells. We investigated the therapeutic potential of Axl inhibition in CML.Experimental Design: We used primary cells from patients with CML and TKI-sensitive and -resistant BCR-ABL1+ CML cell lines and a novel ponatinib-resistant cell line KCL-22 PonR. We analyzed the effects of genetic and pharmacologic Axl blockade by the small-molecule Axl inhibitor BGB324 in vitro and in vivo In BCR-ABL1-unmutated cells, we also investigated BGB324 in combination with imatinib.Results: We demonstrate overexpression of Axl receptor tyrosine kinase in primary cells of patients with CML compared with healthy individuals and a further increase of Axl expression in BCR-ABL TKI-resistant patients. We show that Axl blockage decreased growth of BCR-ABL TKI-sensitive CML cells including CD34+ cells and exerts additive effects with imatinib via inhibition of Stat5 activation. BGB324 also inhibits BCR-ABL TKI-resistant cells, including T315I-mutated and ponatinib-resistant primary cells. BGB324 exerted therapeutic effects in BCR-ABL1 T315I-mutated and ponatinib-resistant preclinical mouse models. Notably, BGB324 does not inhibit BCR-ABL1 and consequently inhibits CML independent of BCR-ABL1 mutational status.Conclusions: Our data show that Axl inhibition has therapeutic potential in BCR-ABL TKI-sensitive as well as -resistant CML and support the need for clinical trials. Clin Cancer Res; 23(9); 2289-300. ©2016 AACR.

Apoptotic index and proliferative index in premalignant and malignant squamous cell lesions of the oral cavity.

BACKGROUND: Oral squamous cell lesions are most commonly diagnosed lesions in India. Both premalignant and malignant lesions are frequently encountered. In this study, we evaluated the role and significance of apoptotic indices (AI) and proliferative indices (PI) in premalignant and malignant squamous cell lesions of the oral cavity. MATERIALS AND METHODS: A total of 62 histologically proven cases of premalignant and malignant oral squamous cell lesions were analyzed. The biopsies were stained with hematoxylin and eosin and also with monoclonal antibody Ki-67. AI and PI were assessed using a light microscope. RESULTS: AI was found to increase gradually from normal to dysplasia to carcinoma. The highest AI was seen in well-differentiated squamous cell carcinomas (SCCs). PI also was found to increase significantly from normal to dysplasia to carcinoma. The highest PI was seen in poorly differentiated SCC. CONCLUSION: AI in conjunction with the PI offers an accurate idea as to the nature and course of the lesion and may help to plan timely surgical intervention that results in better clinical prognosis and outcome.

Cytomegalovirus oesophagitis following treatment with fludarabine for refractory lymphoplasmacytic lymphoma.

A 64-year-old man with a 2-week history of fatigue and fever presented to the medical admissions unit. He had a background of lymphoplasmacytic lymphoma and had recently completed a course of fludarabine-based chemotherapy. CT of the abdomen demonstrated an increase in spleen size and it was thought that his fevers were most likely due to disease recurrence or high-grade transformation. A bone marrow trephine was organised, which showed no evidence of lymphoma and positron emission tomography-CT demonstrated an area of increased avidity at the gastro-oesophageal junction. An oesophagogastroduodenoscopy was recommended, which revealed ulceration within the oesophagus and stomach. Biopsy of the lesions and immunohistochemistry confirmed a diagnosis of cytomegalovirus oesophagitis. He was treated with intravenous ganciclovir followed by oral valganciclovir for a total of 3 weeks. His fever resolved and he was discharged home approximately 8 weeks after he first presented.