PAP Modulations in Daudi Cells and Molt-3 Cells Treated with Etoposide are Mutually Associated with Morphological Evidence of Apoptosis

The effect of the polyadenylation inhibitor cordycepin on human Molt-4 and Daudi leukaemia and lymphoma cell lines

PURPOSE

Posttranscriptional modifications, such as polyadenylation, are very often implicated in the regulation and dysregulation of cell death, through regulation of the expression of specific genes. Based on the fact that an increasing number of adenosine analogues show their antiproliferative and cytotoxic activity via induction of apoptosis, we assessed the effect of cordycepin, a polyadenylation specific inhibitor, an adenosine analogue and a well-known chemotherapeutic drug, on two human leukemia and lymphoma cell lines.

METHODS

Cells were treated with the anticancer drug cordycepin and assessed for poly(A) polymerase (PAP) activity and isoforms by the highly sensitive PAP activity assay and western blotting, respectively. Induction of apoptosis was determined by endonucleosomal DNA cleavage, DAPI staining and Deltapsi(m) reduction, whereas cytotoxicity and cell cycle status were assessed by Trypan blue staining, MTT assay and flow cytometry.

RESULTS AND CONCLUSIONS

The results showed that the differentiated modulations of PAP in the two cell lines may be a result of the additive effect of the changes in cell cycle and apoptotic pathway induced.

The role of cordycepin in cancer treatment via induction or inhibition of apoptosis: implication of polyadenylation in a cell type specific manner

PURPOSE

Most anticancer drugs show their antiproliferative and cytotoxic activity via induction of apoptosis. In the present study we assessed the implication and role of cordycepin, a polyadenylation-specific inhibitor and a well-known chemotherapeutic drug, in apoptosis, induced by the anticancer drug etoposide.

METHODS

For this purpose, a variety of leukemia and lymphoma cell lines (U937, K562, HL-60, Daudi, Molt-4) were treated with the anticancer drugs etoposide and/or cordycepin and assessed for poly(A) polymerase (PAP) activity and isoforms by the highly sensitive PAP activity assay and western blotting, respectively. Induction of apoptosis was determined by endonucleosomal DNA cleavage, DAPI staining, caspase-6 activity assay and DeltaPsi m reduction, whereas cytotoxicity and cell cycle status were assessed by Trypan blue staining, MTT assay and flow cytometry.

RESULTS AND CONCLUSIONS

The results showed that PAP changes in all cell lines, in response to apoptosis induced by etoposide, in many cases even prior to hallmarks of apoptosis (endonucleosomal cleavage of DNA, DeltaPsi(m) reduction). A further elucidation to this apoptosis-polyadenylation correlation was added, by cell treatment with cordycepin, resulting in either suppression (U937, K562) or induction (HL-60) of the apoptotic process, according to the cell type. However, inhibition of polyadenylation did not influence the cell lines Daudi and Molt-4 used, where alternative apoptotic pathways are induced through cleavage of DNA into high molecular weight fragments.