Decreased PARP and procaspase-2 protein levels are associated with cellular drug resistance in childhood acute lymphoblastic leukemia

Abstract

Drug resistance in childhood acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML) is associated with impaired ability to induce apoptosis. To elucidate causes of apoptotic defects, we studied the protein expression of Apaf-1, procaspases-2, -3, -6, -7, -8, -10, and poly(adenosine diphosphate [ADP]-ribose) polymerase (PARP) in cells from children with acute lymphoblastic leukemia (ALL; n ‫؍‬ 43) and acute myeloid leukemia (AML; n ‫؍‬ 10). PARP expression was present in all B-lineage samples, but absent in 4 of 15 T-lineage ALL samples and 3 of 10 AML cases, which was not caused by genomic deletions. PARP expression was a median 7-fold lower in T-lineage ALL (P < .001) and 10-fold lower in AML (P < .001) compared with B-lineage ALL. PARP expression was 4-fold lower in prednisolone, vincristine and L-asparaginase (PVA)-resistant compared with PVA-sensitive ALL patients (P < .001). Procaspase-2 expression was 3-fold lower in T-lineage ALL (P ‫؍‬ .022) and AML (P ‫؍‬ .014) compared with B-lineage ALL. In addition, procaspase-2 expression was 2-fold lower in PVA-resistant compared to PVA-sensitive ALL patients (P ‫؍‬ .042). No relation between apoptotic protease-activating factor 1 (Apaf-1), procaspases-3, -6, -7, -8, -10, and drug resistance was found. In conclusion, low baseline expression of PARP and procaspase-2 is related to cellular drug resistance in childhood acute lymphoblastic leukemia. IntroductionThe treatment of pediatric acute leukemia has greatly improved in the past 4 decades, resulting in long-term disease-free survival of approximately 80% 1 for acute lymphoblastic leukemia (ALL) and 60% for acute myeloid leukemia (AML). 2 Despite this progress, therapy resistance in a significant number of children still forms a major obstacle to successful treatment. We and others have previously shown that ALL patients whose leukemia cells exhibit in vitro resistance to antileukemic agents have a significantly worse prognosis than patients whose leukemic cells are sensitive. [3][4][5][6] Compared with ALL, leukemic cells of children with AML have a less favorable prognosis and are in vitro more resistant to several antileukemic agents. 7 Apoptosis is the predominant form of cell death triggered in vivo and in vitro by chemotherapeutic agents in hematologic malignancies. 8 There are 2 major routes by which apoptosis can be induced: the intrinsic and the extrinsic apoptosis pathways. The intrinsic pathway is initiated by mitochondrial damage that leads to release of cytochrome c from the mitochondrial intermembrane space. 9 Upon entry in the cytoplasm, cytochrome c interacts with apoptotic protease-activating factor 1 (Apaf-1), deoxyadenosine triphosphate (dATP), and procaspase-9 to form a complex known as the apoptosome. 10 In the apoptosome, caspase-9 is activated, which in turn induces processing and activation of downstream effector caspases such as caspases-2, -3, -6, and -7. 11,12 Activation of the effector caspases results in the cleavage of a number of structural and regulatory cellular prot...

Caspase-2 is required for cell death induced by cytoskeletal disruption

“…In contrast, Vinc acts to depolymerize microtubule filaments, whereas cyto D inhibits polymerization of actin filaments and has been shown to activate p53-dependent death (Bhalla, 2003). In addition, there is a correlation between low levels of caspase-2 and resistance to apoptosis in ALL patients treated with drugs such as Vinc (Holleman et al, 2005). Together with our findings these studies further enforce a role for caspase-2 in cytoskeletal damage-induced cell death.…”

“…Lovastatin is an inhibitor of HMG-CoA reductase, an important enzyme in the mevalonate pathway responsible for the synthesis of cholesterol and protein isoprenylation, which includes the isoprenylation of Ras family of GTPases, which are involved in multiple signalling pathways including the control of cell architecture (Green, 2005;Wennerberg et al, 2005). A correlation between low levels of caspase-2 and resistance to apoptosis induced by prednisolone, Vinc and asparagines has been shown in acute lymphoblastic leukaemia (ALL) patients suggesting that caspase-2 might be required for apoptosis induced by these drugs (Holleman et al, 2005).…”

Caspase-2 as a tumour suppressor

“…11 In addition to the identification of caspase-2 somatic mutations in gastric and colorectal cancers, 28 reduced expression of caspase-2 has been correlated with chemotherapeutic drug resistance in childhood acute lymphoblastic leukaemia (ALL). 29 In line with these findings, reduced caspase-2 protein levels have been associated with poor prognosis and outcome in patients with acute myelogenous leukaemia (AML) and ALL. 12,14 Further, analysis of caspase-2 expression from publicly available microarray data demonstrates that, in addition to various haematological malignancies, caspase-2 is downregulated in multiple solid tumours such as hepatocellular and invasive breast carcinomas, ovarian adenocarcinomas and glioblastomas.…”

“…12,14 Reduced levels associated with drug resistance in childhood ALL 29 Chromosomal locus containing caspase-2 gene frequently deleted in cancer 11 Somatic mutations in some gastric tumours 28 Somatic mutations rare in human tumours 31 Not all tumour types show reduced expression of caspase-2…”

Old, new and emerging functions of caspases

“…A tumor suppressor function for caspase-2 was first proposed based on an evidence that the human CASP2 gene region on chromosome 7q is commonly deleted in leukemia. 137 Although somatic mutations of CASP2 are not common in acute leukemia or solid cancers, 138 the reduced expression of caspase-2 is correlated with poor prognosis in some cancers, 139,140 and high caspase-2 levels are associated with remission and survival in adults with ALL and AML. 141 Furthermore, reduced expression and somatic missense mutations in CASP2 have been identified in some gastric and colorectal cancers.…”