Characteristics and outcome of patients with low-/intermediate-risk acute promyelocytic leukemia treated with arsenic trioxide - an international collaborative study

The aim of this study was to characterize a large series of 154 patients with acute promyelocytic leukemia (median age, 53 years; range, 18-90 years) and evaluate real-life outcome after up-front treatment with arsenic trioxide and all-trans retinoic acid. All patients were included in the prospective NAPOLEON registry (NCT02192619) between 2013 and 2019. The acute promyelocytic leukemia was de novo in 91% (n=140) and therapy-related in 9% (n=14); 13% (n=20) of the patients were older than 70 years. At diagnosis bleeding/hemorrhage was present in 38% and thrombosis in 3%. Complete remission was achieved in 152 patients (99%), whereas two patients (1%) experienced induction death within 18 days after starting therapy. With a median follow-up of 1.99 years (95% confidence interval: 1.61-2.30 years) 1-year and 2-year overall survival rates were 97% (95% confidence interval: 94-100%) and 95% (95% confidence interval: 91-99%), respectively. Age above 70 years was associated with a significantly shorter overall survival (P<0.001) compared to that of younger patients. So far no relapses have been observed. Six patients (4%) died in complete remission at a median of 0.95 years after diagnosis (range, 0.18-2.38 years). Our data confirm the efficiency and durability of arsenic trioxide and all-trans retinoic acid therapy in the primary management of adults with low-/intermediate-risk acute promyelocytic leukemia in the real-life setting, irrespective of age.

A subgroup of pleural mesothelioma expresses ALK protein and may be targetable by combined rapamycin and crizotinib therapy

Malignant pleural mesothelioma (MPM) is a neoplasm with inferior prognosis and notorious chemotherapeutic resistance. Targeting aberrantly overexpressed kinases to cure MPM is a promising therapeutic strategy. Here, we examined ALK, MET and mTOR as potential therapeutic targets and determined the combinatorial efficacy of ALK and mTOR targeting on tumor cell growth in vivo.

First, ALK overexpression, rearrangement and mutation were studied in primary MPM by qRT-PCR, FISH, immunohistochemistry and sequence analysis; mTOR and MET expression by qRT-PCR and immunohistochemistry. Overexpression of full-length ALK transcripts was observed in 25 (19.5%) of 128 primary MPM, of which ten expressed ALK protein. ALK overexpression was not associated with gene rearrangement, amplification or kinase-domain mutation. mTOR protein was detected in 28.7% MPM, co-expressed with ALK or MET in 5% and 15% MPM, respectively. The ALK/MET inhibitor crizotinib enhanced the anti-tumor effect of the mTOR-inhibitor rapamycin in a patient-derived MPM xenograft with co-activated ALK/mTOR: combined therapy achieved tumor shrinkage in 4/5 tumors and growth stagnation in one tumor. Treatment effects on proliferation, apoptosis, autophagy and pathway signaling were assessed using Ki-67 immunohistochemistry, TUNEL assay, LC3B immunofluorescence, and immunoblotting. Co-treatment significantly suppressed cell proliferation and induced autophagy and caspase-independent, necrotic cell death. Rapamycin/crizotinib simultaneously inhibited mTORC1 (evidenced by S6 kinase and RPS6 dephosphorylation) and ALK signaling (ALK, AKT, STAT3 dephosphorylation), and crizotinib suppressed the adverse AKT activation induced by rapamycin.

In conclusion, co-treatment with rapamycin and crizotinib is effective in suppressing MPM tumor growth and should be further explored as a therapeutic alternative in mesothelioma.

Abstract 1224: Combination of rapamycin and crizotinib induces partial remission of pleural mesothelioma in a patient-derived xenograft model

Introduction: Malignant pleural mesothelioma (MPM) is a neoplasm with inferior prognosis and notorious chemotherapeutic resistance. New treatment approaches may be based on specific inhibitors against kinases that are overexpressed in MPM, such as mTOR and MET. Here we examined the tyrosine kinase ALK as a potential therapeutic target and the combinatorial efficacy of the ALK/MET inhibitor crizotinib and the mTOR inhibitor rapamycin.

Methods: We investigated the ALK status and the expression of mTOR and MET in 145 primary MPM and 8 murine patient-derived xenograft models. ALK overexpression, rearrangement and mutation were studied by qRT-PCR, FISH, immunohistochemistry and sequence analysis. Expression of mTOR and MET was analyzed by qRT-PCR and immunohistochemistry. The combined anti-tumor effect of crizotinib and rapamycin was evaluated in a patient derived xenograft model. Effects of single drug vs. combination treatment on proliferation, apoptosis and autophagy were assessed using Ki-67 immunohistochemistry, TUNEL assay and LC3B immunofluorescence, respectively.

Results: Overexpression of ALK transcripts was detected in 25 (19.5%) of 128 interpretable primary MPM and two xenograft tumors and was neither associated with ALK rearrangement nor with mutation of the kinase domain. ALK protein was expressed in 8.3% MPM and the two xenograft tumors expressing ALK transcript. mTOR protein expression was detected in 28.7% MPM, co-expressed with ALK and/or MET in 17.8% MPM. Applied to a patient derived MPM xenograft model that co-expressed ALK, MET and mTOR, crizotinib alone did not exert anti-tumor growth activity, but enhanced the anti-tumor effect of rapamycin: Rapamycin was effective in 3 of 5 tumors (pathological partial remission in 1, stable tumor in 2 cases). Combination treatment was active in all 5 tumors (partial remission in 4, stable tumor in 1 case). Simultaneous treatment with rapamycin and crizotinib, however, significantly suppressed tumor proliferation compared to rapamycin-single treatment. Autophagy was induced by both single drug treatments and distinctly enhanced by combination treatment, while apoptosis was not promoted.

Conclusion: Dual combinatory treatment of rapamycin and crizotinib is more effective than rapamycin as single agent in suppressing MPM tumor growth and therefore merits further investigation.

Citation Format: Dina Mönch, Sabine Bode-Erdmann, Jörg Kalla, Jörn Sträter, Carsten Schwänen, Roger-Fei Falkenstern-Ge, Martin Kimmich, Martin Kohlhäufl, Godehard Friedel, German Ott, Claudia Kalla. Combination of rapamycin and crizotinib induces partial remission of pleural mesothelioma in a patient-derived xenograft model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1224. doi:10.1158/1538-7445.AM2017-1224

CD30-induced up-regulation of the inhibitor of apoptosis genes cIAP1 and cIAP2 in anaplastic large cell lymphoma cells

OBJECTIVE

Expression of the cytokine receptor CD30 is a typical feature of anaplastic large cell lymphomas (ALCL). CD30-induced effects have a great impact on cell activation and viability.

MATERIALS AND METHODS

Using Karpas 299 cells, we performed differential display reverse transcriptase polymerase chain reaction (DDRT-PCR) to identify novel genes involved in CD30 signaling in ALCL. Activation of CD30 was induced by treatment with immobilized anti-CD30 antibody. RNA and protein expression were confirmed in different cell lines by Northern and Western blot analysis. Fluorescence-activated cell sorting (FACS) analysis was applied to examine cell viability. Nuclear factor kappaB (NFkappaB) pathways were blocked using a specific inhibitor.

RESULTS

We found strongly enhanced expression of the cellular inhibitor of apoptosis cIAP1 and cIAP2 in Karpas 299 cells stimulated with anti-CD30. Furthermore, we showed that CD30-regulated expression of cIAP1 and cIAP2 was mediated by NFkappaB. Induction of NFkappaB, cIAP1, and cIAP2 correlated with partial protection from apoptotic cell death caused by etoposide. Correspondingly, inhibition of the NFkappaB pathway not only prevented the prevalent antiapoptotic effects mediated by CD30, but even led to CD30-induced apoptosis. Finally, we found enhanced expression of cIAP1 and cIAP2 in several other ALCL cell lines and the HD-derived cell line HDLM-2 upon CD30 stimulation.

CONCLUSIONS

Our results indicate that CD30-mediated protection from apoptosis is a common feature of CD30(+) cells. Therefore, CD30-induced signaling may have a significant impact on the clinical outcome of patients with ALCL.

In vitro evaluation of bendamustine induced apoptosis in B-chronic lymphocytic leukemia

Bendamustine is a novel cytostatic agent, with activity in non-Hodgkin's lymphomas including B-chronic lymphocytic leukemia (B-CLL). The knowledge about its mode of action, however, is still limited. Here, we investigated the in vitro ability of bendamustine to induce apoptosis on freshly isolated peripheral lymphocytes in B-CLL and analyze the potential underlying mechanisms of action for inducing apoptosis. In CLL cells taken from 37 previously treated and untreated CLL patients, we investigated the influence of bendamustine alone, and in combination with fludarabine, on the induction of apoptosis and changes of Bcl-2 and Bax expression on mRNA and protein level using the RNase protection assay or flow cytometry, respectively. Apoptotic cells were determined with flow cytometry using the fluorescent DNA-binding agent 7-ADD. Using bendamustine alone in concentrations from 1 microg/ml to 50 microg/ml, a dose- and time-dependent manner of cytotoxicity from 30.4% to 94.8% after 48 h could be observed. The LD50 for untreated and pretreated CLL cells was 7.3 or 4.4 microg/ml, respectively. The median apoptotic rate was similar in both groups. The combination of bendamustine with fludarabine led to a highly synergistic effect in inducing apoptosis, which was 150% higher than expected for bendamustine plus fludarabine. The level of the initial Bcl-2 and Bax protein and the m-RNA expression remained unchanged during the incubation with bendamustine. In conclusion, this study demonstrates for the first time the in vitro efficacy of bendamustine in inducing apoptosis in B-CLL cells alone and in combination with fludarabine.