Octylcaffeate induced apoptosis in human leukemia U937 cells.

We found that octylcaffeate, a semisynthetic caffeic acid derivative, strongly inhibited the growth of human histiolytic lymphoma U937 cells in a dose- and time-dependent manner via apoptosis. Octylcaffeate induced the fragmentation of DNA into multiples of 180 bp (an apoptotic DNA ladder) and condensation of chromatin, and increased the percentage of hypodiploid cells detected with a flow cytometer. DNA fragmentation induced by octylcaffeate was inhibited by pretreatment with Z-DEVD-FMK and Z-Asp-CH(2)D-CB, an inhibitor of caspase, clearly showing that the mode of cell death is apoptotic. These findings suggest that the cytotoxicity of octylcaffeate involves the induction of apoptosis.

RU486-inducible retrovirus-mediated caspase-3 overexpression is cytotoxic to bcl-xL-expressing myeloma cells in vitro and in vivo.

The antiapoptotic protein bcl-x(L) is upregulated in a variety of solid tumors and in primary hematologic malignancies such as multiple myeloma. Activated caspase-3 cleaves proteins essential for cell survival, including bcl-x(L). To explore the potential of caspase-3 as a cytotoxic and immunostimulatory molecule in the treatment of malignancy, an RU486-inducible caspase-3 retrovirus was constructed, validated, and used to transduce first 3T3 and subsequently murine myeloma B9BM1 cells (creating the cell line B9BM-C3). After induction, apoptotic cell death of 3T3 and B9BM-C3 cells began by 4 h and was complete by 48 h postinduction, while nontransduced cells remained viable. Annexin V staining demonstrated 43, 76, and 98% apoptotic cell death at 12, 18, and 24 h postinduction. Activation of caspase-3 was evident in induced cells and cell death could be inhibited by the addition of a caspase-3-specific inhibitor. Overexpression of the myeloma-associated oncogene FGFR3, which upregulates bcl-x(L), delayed but did not prevent caspase-3-mediated killing. B9BM-C3 cells formed tumors after subcutaneous injection in mice. Early treatment with RU486 eradicated tumors; however, rechallenge of treated mice failed to demonstrate evidence of immunoprotection. These results indicate that therapeutic attempts to induce caspase-3 in malignant cells may prove useful in the treatment of bcl-x(L)-expressing tumors.

The caspase-derived C-terminal fragment of betaAPP induces caspase-independent toxicity and triggers selective increase of Abeta42 in mammalian cells.

During its physiopathological maturation, the beta-amyloid precursor protein undergoes several distinct proteolytic events by activities called secretases. In Alzheimer's disease, the main histological hallmark called senile plaque is clearly linked to the overproduction of the amyloid peptides Abeta40 and Abeta42, two highly aggregable betaAPP-derived fragments generated by combined cleavages by beta- and gamma-secretases. Recently, an alternative hydrolytic pathway was described, involving another category of proteolytic activities called caspases, responsible for the production of a 31 amino acids betaAPP C-terminal fragment called C31. C31 was reported to lower the viability of N2a cells but the exact mechanisms mediating C31-toxicity remained to be established. Here we show that the transient transfection of pSV2 vector encoding C31 lowers by about 80% TSM1 neuronal cells viability. Arguing against a C31-stimulated apoptotic response, we demonstrate by combined enzymatic and immunological approaches that C31 expression did not modulate basal or staurosporine-induced caspase 3-like activity and pro-caspase-3 activation. Furthermore, C31 did not modify Bax and p53 expressions, poly-(ADP-ribose)-polymerase cleavage and cytochrome c translocation into the cytosol. However, we established that C31 overexpression triggers selective increase of Abeta42 but not Abeta40 production by HEK293 cells expressing wild-type betaAPP751. Altogether, our data demonstrate that C31 induces a caspase-independent toxicity in TSM1 neurons and potentiates the pathogenic betaAPP maturation pathway by increasing selectively Abeta42 species in wild type-betaAPP-expressing human cells.

Caspases: more than just killers?

Proteases of the caspase family constitute the central executioners of apoptosis. Several recent observations suggest that caspases and apoptosis-regulatory molecules exert important functions beyond that of cell death, including the control of T-cell proliferation and cell-cycle progression. Here, Los and colleagues propose a model that directly connects cell suicide mechanisms to the regulation of cell-cycle progression.