Functional analysis of apoptosis induction in acute myeloid leukaemia‐relevance of karyotype and clinical treatment response

Abstract

Summary Deficiencies or structural defects of the apoptotic machinery have been postulated as a potential mechanism for a broad resistance of acute myeloid leukaemia (AML) blasts towards cytotoxic therapy comprising chemotherapeutic agents with diverse pharmacodynamic principles but also cell‐mediated cytotoxicity of the graft‐versus‐leukaemia effect, for example, in the setting of allogeneic transplantation. This hypothesis was systematically tested by functionally analysing the early, intermediate and late events of the apoptotic process in primary AML (n = 31) blasts following activation of the intrinsic and extrinsic pathway of apoptosis (etoposide and cytarabine as DNA damaging agents, FAS‐ligand as an activator of the death receptor pathway). Activation of the extrinsic pathway by FAS‐ligand did not induce apoptosis in primary AML, instead the proapoptotic signal was shown to ‘fade’, even in the early phase of the apoptotic sequence. However, activation of the intrinsic pathway induced severe cytotoxicity in all samples that showed the characteristic features of typical apoptosis, with a prominent apoptotic volume decrease (blebbing) in the early phase, significant increases in caspase 3 activity (intermediate or effector phase) and breakdown of cellular energy production in the late phase of apoptosis. These characteristics did not differ between prognostically favourable versus unfavourable AML karyotypes or between clinically responding versus refractory AML – indicating that a functional apoptotic apparatus is present even in the unfavourable AML subgroups . Our data indicate that the mechanism for a broad clinical resistance is not a dysfunctional apparatus per se but rather the consequence of anti‐apoptotic regulation impeding otherwise functional apoptotic machinery.

Early prediction of therapy response in patients with acute myeloid leukemia by nucleosomal DNA fragments

“…Antileukemic drugs like cytarabine in combination with daunorubicine and 6-thioguanine (TAD), or with mitoxantrone (HAM) cause DNA damage or inhibit DNA synthesis and, thus, kill tumor cells mainly by apoptosis [ 30 ]. The activation of caspases-3 and caspases-8 was already detected 12–24 hours after the application of the chemotherapeutic drugs [ 31 , 32 ]. Also morphologically, increasing numbers of apoptotic cells were observed after application of the cytotoxic therapy; for example mitoxantrone induced early apoptosis and showed a high rate of cell death of blast cells during the initial 24 hours [ 14 ].…”

“…Also morphologically, increasing numbers of apoptotic cells were observed after application of the cytotoxic therapy; for example mitoxantrone induced early apoptosis and showed a high rate of cell death of blast cells during the initial 24 hours [ 14 ]. Another study reported cytarabine to induce cytotoxicity and to reduce the viability of bone marrow blasts by two thirds 24 hours and almost completely 96 hours after application of the drug [ 32 ].…”

Glyceraldehyde 3-Phosphate Dehydrogenase Depletion Induces Cell Cycle Arrest and Resistance to Antimetabolites in Human Carcinoma Cell Lines

“…Caspase 3 activation is not required for necrosis, and occurs very late or not at all in autophagy; it might therefore differentiate between these modes of cell death (Braess et al, 2004;Levine and Yuan, 2005). An intriguing feature of GAPDH is its intranuclear accumulation in response to nongenotoxic and genotoxic stimuli.…”

Remission induction chemotherapy induces in vivo caspase‐dependent apoptosis in bone marrow acute myeloid leukemia blast cells and spares lymphocytes

“…Each case was classified according to the FrenchAmerican-British (FAB) system (23). Cytogenetic abnormalities were classified as follows (24,25): favorable, inv (16) and t (8,21); unfavorable, abnormalities of chromosomes 5 and/or 7 and abnormalities involving 11q23 and complex abnormalities; intermediate, all other abnormalities. The hematological characteristics are summarized in Table 1 …”

“…The mechanisms of resistance are complex (1,(8)(9)(10)(11)(12) and do not clearly come from a dysfunctional apoptotic apparatus per se, but rather from a regulation impeding otherwise functional apoptotic machinery. These adaptive phenomena could impair the ability to achieve a durable complete remission (CR) with chemotherapy, leading to a relapse following CR, indicating that a part of the initial leukemic cells was withdrawn from the chemotherapy-induced cell death.…”