New therapeutic strategy for Acute Promyelocytic Leukemia & novel mutations

12 Oct 2016

New therapeutic strategy for Acute Promyelocytic Leukemia & novel mutations

Novel therapeutic strategy for Acute Promyelocytic Leukemia (APL) and  novel mutations in APL patients

By Dr Vikram Mathews, Senior Fellow

CMC Vellore

Acute promyelocytic leukemia (APL), a type of cancer of the white blood cells, is characterized by mutations in a novel PML-RARA  oncogene (1-4). Arsenic trioxide (ATO) has proven efficacy as first line therapy in the treatment of acute promyelocytic leukemia (APL) (5). The relative specificity of ATO in the treatment of APL results from the ability of ATO to bind directly to the PML (promyelocytic leukemia) and chimeric PML-RARA (promyelocytic leukemia–retinoic acid receptor-α) protein which in turn leads to its degradation inside the cell. The existing literature suggests that this degradation is mediated by intra-cellular organelles called proteasomes (6, 7). Based on the current understanding of the mechanism of action of ATO in APL, proteasomal inhibition would be antagonistic to the action of ATO.

We had previously reported, in an in vitro model, that there was evidence of significant microenvironment mediated de novo drug resistance (EM-DR) to ATO (8). This suggests that malignant cells residing in specific micro-environments as in the bone marrow were likely to be more resistant to treatment than when they were removed from this environment. We had also demonstrated that co-culturing malignant cells with stromal cells in vitro (mimicking the effect of the micro-environment in vitro) resulted in upregulation of the NF-κB pathway in malignant cells and inhibiting this pathway could overcome the micro-environment mediated drug resistance to ATO. Further, we had recently reported that by using a proteasome inhibitor (bortezomib)(9)we could overcome such drug resistance and that this drug synergizes with ATO in the treatment of APL.

On a separate note there has been a recent concern of ATO resistance in patients treated with upfront ATO (10). The focus of ATO resistance has centered on mutations in PML-RARA gene (10-12), specifically missense or point mutations in the B2 domain of the PML gene that results in the inability of ATO to directly bind to the PML and PML-RARA oncoprotein leading to resistance (12). While additional mutations have been noted in up to a third of relapsed APL patients in the PML-RARA gene it is not clear whether such mutations are associated with secondary ATO  resistance as described for those in the PML B2 domain (10). However, the published data suggests that patients with such mutations have an unfavorable clinical outcome (10-12). There is a need to address novel strategies and therapeutic modalities to treat relapsed APL, especially those that have received ATO as upfront therapy.

Our in vitro observation of a possible synergistic cytotoxic effect of combining bortezomib, a proteasome inhibitor, and ATO on malignant promyelocyte in a stromal co-culture system was contradictory to existing dogma on the mechanism of action of ATO.  The mechanism of such a synergy has not been previously evaluated and the theoretical antagonism of combining these two agents on PML and PML-RARA degradation, which is central to clearance of the leukemia initiating compartment in APL and achieving cure (12, 13)has not been previously addressed. In this study we evaluated the mechanism of bortezomib induced cytotoxicity against malignant promyelocytes, its potential mechanism of synergy with ATO and the fate of PML-RARA when this combination was used.

We demonstrate an alternative mechanism of PML-RARA degradation following treatment with ATO and bortezomib and also demonstrate synergy between these two agents. Through a series of in-vitro experiments, animal models and preliminary clinical trial data we have validated the beneficial effect of this combination in the management of APL. Most interestingly this combination is highly effective against ATO resistant APL cell lines and in patients with relapsed APL (14).

The overall management of APL has evolved into a de-escalation strategy from intensive myelo-toxic combination chemotherapy to non myelo-toxic regimens (15). This evolution has been achieved by remarkable progress in the understanding of the biology of the disease and the mechanism of action of agents, such as ATO and ATRA, used to treat this condition. Data in this research publication along the same lines, demonstrates the potential of the use of another non-myelotoxic agent (proteasome inhibitor) in combination with ATO being effective even in ATO resistant and relapsed APL. The potential is that this group of drugs could replace potent myelo-toxic anthracylines even in high risk and relapsed APL where they continue to be used in standard of care.

These observations bring to the forefront novel biology, illustrate new therapeutic targets and have significant translational potential which could have a bearing on other leukemia’s and cancers beyond APL.

In another study, in collaboration with Dr. Phillip Koeffler’s laboratory at National University of Singapore, we did an international multi-center co-operative study to comprehensively analyze the spectrum of mutations in newly diagnosed and relapsed APL. As previously reported we also noted the frequent mutations in the PML and PML-RARA genes in relapsed APL patients in comparison to newly diagnosed patients. Additionally, we demonstrated an increased frequency of previously unidentified mutations in the ARID1B and ARID1A genes in relapsed patients and the potential mechanism by which they mediate drug resistance in relapsed patients(16).

These two publications together address the pathological mechanisms of drug resistance and relapse in acute promyelocytic leukemia along with a novel combination of approved drugs to overcome such resistance and improve clinical outcomes in these patients.  

Rationale and efficacy of proteasome inhibitor combined with arsenic trioxide in the treatment of acute promyelocytic leukemia. Ganesan S1, Alex AA1, Chendamarai E, Balasundaram N, Palani HK, David S, Kulkarni U, Aiyaz M, Mugasimangalam R, Korula A, Abraham A,Srivastava A, Padua RA, Chomienne C, George B, Balasubramanian P, Mathews V.Leukemia. 2016 Sep 2. doi: 10.1038/leu.2016.227

Comprehensive mutational analysis of primary and relapse acute promyelocytic leukemia.
Madan V, Shyamsunder P, Han L, Mayakonda A, Nagata Y, Sundaresan J, Kanojia D, Yoshida K, Ganesan S, Hattori N, Fulton N, Tan KT,Alpermann T, Kuo MC, Rostami S, Matthews J, Sanada M, Liu LZ, Shiraishi Y, Miyano S, Chendamarai E, Hou HA, Malnassy G, Ma T, Garg M, Ding LW, Sun QY, Chien W, Ikezoe T, Lill M, Biondi A, Larson RA, Powell BL, Lübbert M, Chng WJ, Tien HF, Heuser M,Ganser A, Koren-Michowitz M, Kornblau SM, Kantarjian HM, Nowak D, Hofmann WK, Yang H, Stock W, Ghavamzadeh A, Alimoghaddam K, Haferlach T, Ogawa S, Shih LY, Mathews V, Koeffler HP. Leukemia. 2016 Aug;30(8):1672-81. doi: 10.1038/leu.2016.69. Epub 2016 Apr 11.



1.            de The H, Chomienne C, Lanotte M, Degos L, Dejean A. The t(15;17) translocation of acute promyelocytic leukaemia fuses the retinoic acid receptor alpha gene to a novel transcribed locus. Nature. 1990;347(6293):558-61.

2.            Borrow J, Goddard AD, Sheer D, Solomon E. Molecular analysis of acute promyelocytic leukemia breakpoint cluster region on chromosome 17. Science. 1990;249(4976):1577-80.

3.            Kakizuka A, Miller WH, Jr., Umesono K, Warrell RP, Jr., Frankel SR, Murty VV, et al. Chromosomal translocation t(15;17) in human acute promyelocytic leukemia fuses RAR alpha with a novel putative transcription factor, PML. Cell. 1991;66(4):663-74.

4.            Longo L, Pandolfi PP, Biondi A, Rambaldi A, Mencarelli A, Lo Coco F, et al. Rearrangements and aberrant expression of the retinoic acid receptor alpha gene in acute promyelocytic leukemias. J Exp Med. 1990;172(6):1571-5.

5.            Mathews V, George B, Chendamarai E, Lakshmi KM, Desire S, Balasubramanian P, et al. Single-agent arsenic trioxide in the treatment of newly diagnosed acute promyelocytic leukemia: long-term follow-up data. J Clin Oncol. 2010;28(24):3866-71.

6.            Lallemand-Breitenbach V, Jeanne M, Benhenda S, Nasr R, Lei M, Peres L, et al. Arsenic degrades PML or PML-RARalpha through a SUMO-triggered RNF4/ubiquitin-mediated pathway. Nat Cell Biol. 2008;10(5):547-55.

7.            Zhang XW, Yan XJ, Zhou ZR, Yang FF, Wu ZY, Sun HB, et al. Arsenic trioxide controls the fate of the PML-RARalpha oncoprotein by directly binding PML. Science. 2010;328(5975):240-3.

8.            Chendamarai E, Ganesan S, Alex AA, Kamath V, Nair SC, Nellickal AJ, et al. Comparison of newly diagnosed and relapsed patients with acute promyelocytic leukemia treated with arsenic trioxide: insight into mechanisms of resistance. PLoS One. 2015;10(3):e0121912.

9.            Ganesan S, Chendamarai E, Rao JG, Hareendran S, Alex AA, Ahmed R, et al. Rationale and Efficacy of Bortezomib in the Treatment of Acute Promyelocytic Leukemia in Combination with Arsenic Trioxide: In-Vitro and Phase I Data. ASH Annual Meeting Abstracts. 2011;118(21):947-.

10.          Zhu HH, Qin YZ, Huang XJ. Resistance to arsenic therapy in acute promyelocytic leukemia. N Engl J Med. 2014;370(19):1864-6.

11.          Goto E, Tomita A, Hayakawa F, Atsumi A, Kiyoi H, Naoe T. Missense mutations in PML-RARA are critical for the lack of responsiveness to arsenic trioxide treatment. Blood. 2011;118(6):1600-9.

12.          Lehmann-Che J, Bally C, de The H. Resistance to therapy in acute promyelocytic leukemia. N Engl J Med. 2014;371(12):1170-2.

13.          Nasr R, Guillemin MC, Ferhi O, Soilihi H, Peres L, Berthier C, et al. Eradication of acute promyelocytic leukemia-initiating cells through PML-RARA degradation. Nat Med. 2008;14(12):1333-42.

14.          Ganesan S, Alex AA, Chendamarai E, Balasundaram N, Palani HK, David S, et al. Rationale and efficacy of proteasome inhibitor combined with arsenic trioxide in the treatment of acute promyelocytic leukemia. Leukemia. 2016.

15.          Mathews V. De-escalation of treatment for acute promyelocytic leukaemia? The Lancet Haematology. 2015;2(9):e348-e9.

16.          Madan V, Shyamsunder P, Han L, Mayakonda A, Nagata Y, Sundaresan J, et al. Comprehensive mutational analysis of primary and relapse acute promyelocytic leukemia. Leukemia. 2016;30(8):1672-81.


Image Credit Wellcome Photo Library, Wellcome Images. Photomicrograph of peripheral blood in acute promyelocytic leukaemia. Shows abnormal immature myeloblastic and promyelocytic white cells.