Protease Activation in Apoptosis Induced by MAL

Köhler, Camilla; Håkansson, Anders; Svanborg, Catharina; Orrenius, Sten; Zhivotovsky, Boris

doi:10.1006/excr.1999.4472

Cited by 69 publications

(85 citation statements)

References 23 publications

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“…A previous study reported that cytochrome c release and caspase activation are involved in MAL-induced apoptosis in transformed cells [8]. MAL was internalized into the cytoplasm and co-localized with mitochondria.…”

Section: Discussionmentioning

confidence: 85%

“…However, the exact mechanisms of apoptosis induction by MAL are unknown. Previous data have shown that release of cytochrome c and activation of the caspase cascade are early events during MAL-induced killing [8]. Co-localization of MAL with mitochondria suggested that MAL may induce apoptosis via a direct interaction with mitochondria, which leads to the release of cytochrome c into the cytosol.…”

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confidence: 93%

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A folding variant of human α‐lactalbumin induces mitochondrial permeability transition in isolated mitochondria

Köhler

Gogvadze

Håkansson

et al. 2001

European Journal of Biochemistry

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A human milk fraction containing multimeric a-lactalbumin (MAL) is able to kill cells via apoptosis. MAL is a protein complex of a folding variant of a-lactalbumin and lipids. Previous results have shown that upon treatment of transformed cells, MAL localizes to the mitochondria and cytochrome c is released into the cytosol. This is followed by activation of the caspase cascade. In this study, we further investigated the involvement of mitochondria in apoptosis induced by the folding variant of a-lactalbumin. Addition of MAL to isolated rat liver mitochondria induced a loss of the mitochondrial membrane potential (DC m ), mitochondrial swelling and the release of cytochrome c. These changes were Ca 21 -dependent and were prevented by cyclosporin A, an inhibitor of mitochondrial permeability transition. MAL also increased the rate of state 4 respiration in isolated mitochondria by exerting an uncoupling effect. This effect was due to the presence of fatty acids in the MAL complex because it was abolished completely by BSA. BSA delayed, but failed to prevent, mitochondrial swelling as well as dissipation of DC m , indicating that the fatty acid content of MAL facilitated, rather than caused, these effects. Similar results were obtained with HAMLET (human a-lactalbumin made lethal to tumour cells), which is native a-lactalbumin converted in vitro to the apoptosis-inducing folding variant of the protein in complex with oleic acid. Our findings demonstrate that a folding variant of a-lactalbumin induces mitochondrial permeability transition with subsequent cytochrome c release, which in transformed cells may lead to activation of the caspase cascade and apoptotic death.Keywords: a-lactalbumin; cytochrome c; mitochondria; mitochondrial permeability transition; tumour cells.Diverse physiological and pathological stimuli can induce apoptosis by distinct pathways that converge in a common programme of cell suicide. Upon apoptotic triggering, a unique family of cysteine aspartate proteases, caspases, becomes activated [1]. In many models of apoptosis, caspase activation requires the release of apoptogenic factors, such as cytochrome c, from the mitochondrial intermembrane space. Once released into the cytosol, cytochrome c binds to Apaf-1, and together with pro-caspase-9 and dATP, forms the so-called apoptosome complex [2]. This association leads to the activation of pro-caspase-9 which, in turn, initiates the caspase cascade by activating pro-caspase-3. Although cytochrome c release has been observed in many experimental models of apoptosis, the precise mechanism responsible for its movement across the outer mitochondrial membrane remains unclear. Different hypotheses have been proposed [3]. Cytochrome c may be released via specific channels in the outer mitochondrial membrane or the release may be a consequence of mitochondrial swelling leading to the rupture of the outer mitochondrial membrane. Mitochondrial swelling may be due to opening of the mitochondrial permeability transition (MPT) pore, a polyprotein complex fo...

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Section: Discussionmentioning

confidence: 85%

mentioning

confidence: 93%

A folding variant of human α‐lactalbumin induces mitochondrial permeability transition in isolated mitochondria

Köhler

Gogvadze

Håkansson

et al. 2001

European Journal of Biochemistry

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“…HAMLET has been reported to induce apoptotic cell death characterized by cytochrome c release and caspase-dependent chromatin condensation (13). However, further studies have revealed that ectopic expression of the antiapoptotic protein Bcl-2 and inhibition of caspases by zVAD-fmk fail to rescue the cells from HAMLETinduced cytotoxicity (12).…”

Section: Bamlet Induces Caspase-independent Apoptosislike Cell Death mentioning

confidence: 99%

“…Although HAMLET can activate apoptotic caspases in some target cells, these enzymes are not required for its cytotoxic effect (12,13). The nonapoptotic nature of HAMLETinduced cytotoxicity is further emphasized by its ability to kill tumor cells that have acquired resistance to classic apoptosis pathway either by overexpressing the antiapoptotic protein Bcl-2 or by carrying mutations in the p53 tumor suppressor protein (12).…”

Section: Introductionmentioning

confidence: 99%

BAMLET Activates a Lysosomal Cell Death Program in Cancer Cells

Rammer

Groth‐Pedersen

Kirkegaard

et al. 2010

Molecular Cancer Therapeutics

120

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A complex of human α-lactalbumin and oleic acid (HAMLET) was originally isolated from human milk as a potent anticancer agent. It kills a wide range of transformed cells of various origins while leaving nontransformed healthy cells largely unaffected both in vitro and in vivo. Importantly, purified α-lactalbumins from other mammals form complexes with oleic acid that show biological activities similar to that of HAMLET. The mechanism by which these protein-lipid complexes kill tumor cells is, however, largely unknown. Here, we show that complex of bovine α-lactalbumin and oleic acid (BAMLET), the bovine counterpart of HAMLET, kills tumor cells via a mechanism involving lysosomal membrane permeabilization. BAMLET shows potent cytotoxic activity against eight cancer cell lines tested, whereas nontransformed NIH-3T3 murine embryonic fibroblasts are relatively resistant. BAMLET accumulates rapidly and specifically in the endolysosomal compartment of tumor cells and induces an early leakage of lysosomal cathepsins into the cytosol followed by the activation of the proapoptotic protein Bax. Ectopic expression of three proteins known to stabilize the lysosomal compartment, i.e. heat shock protein 70 (Hsp70), Hsp70-2, and lens epithelium-derived growth factor, confer significant protection against BAMLET-induced cell death, whereas the antiapoptotic protein Bcl-2, caspase inhibition, and autophagy inhibition fail to do so. These data indicate that BAMLET triggers lysosomal cell death pathway in cancer cells, thereby clarifying the ability of α-lactalbumin:oleate complexes to kill highly apoptosis-resistant tumor cells. Mol Cancer Ther; 9(1); 24-32. ©2010 AACR.

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“…This complex has been reported to induce cell death in a plethora of cancer cell lines, whereas normal cells are resistant Hallgren et al, 2008). It has been postulated that HAMLET might interact and perturb the functioning of the mitochondria (Kohler et al, 1999), proteosome ) and histones , inducing features of multimembrane autophagosomes and suggesting that macroautophagy might contribute to tumor cell death . Although it has been demonstrated that normal and tumor cells display different features for the subcellular localization and internalization of HAMLET (suggesting the existence of active shuttling mechanisms), neither the receptors involved nor the mechanisms orchestrating the protein uptake have been identified.…”

Section: Strategies To Selectively Kill Tumor Cellsmentioning

confidence: 99%

Towards novel paradigms for cancer therapy

et al. 2010

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Cancer is a complex progressive multistep disorder that results from the accumulation of genetic and epigenetic abnormalities, which lead to the transformation of normal cells into malignant derivatives. Despite enormous progress in the understanding of cancer biology including the decryption of multiple regulatory networks governing cell growth and death, and despite the possibility of analyzing (epi)genetic deregulation at the genome-wide scale, cancertargeted therapy is still the exception. In fact, to date there are still far too few examples of therapies leading to cure; treatment-derived toxicity is a major issue, and cancer remains to be one of the largest causes of death worldwide. The purpose of this review is to discuss the state of the art of cancer therapy with respect to the key issue of any treatment, namely its target selectivity. Therefore, we recapitulate and discuss current concepts and therapies targeting tumorspecific features, including oncofusion proteins, aberrant kinase activities and epigenetic tumor makeup. We analyze strategies designed to induce tumor-selective death such as the use of oncolytic virus, tumoricidal proteins (NS1, Eorf4, apoptin, HAMLET (human a-lactalbumin made lethal to tumor cells)) and activation of signaling pathways involved in tumor surveillance. We emphasize the potential of the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) pathway, an essential component of the evolutionary developed defense systems that eradicate malignant cells. Finally, we discuss the necessity of targeting tumor-initiating cells (TICs) to avoid relapse and increase the chances of complete remission, and describe emerging concepts that might provide novel avenues for cancer therapy.

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Protease Activation in Apoptosis Induced by MAL

Cited by 69 publications

References 23 publications

A folding variant of human α‐lactalbumin induces mitochondrial permeability transition in isolated mitochondria

A folding variant of human α‐lactalbumin induces mitochondrial permeability transition in isolated mitochondria

BAMLET Activates a Lysosomal Cell Death Program in Cancer Cells

Towards novel paradigms for cancer therapy

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