Topoisomerase-I inhibitors for human malignant glioma: Differential modulation of p53, p21, bax and bcl-2 expression and of CD95-mediated apoptosis by camptothecin and β-lapachone

Abstract

β‐lapachone and camptothecin are structurally unrelated agents thought to inhibit topoisomerase‐I activity through distinct mechanisms. We find that β‐lapachone is much more potent than camptothecin in inducing acute cytotoxic effects on human malignant glioma cells. Acute cytotoxicity induced by both drugs is apoptotic by electron microscopy, but not blocked by inhibitors of RNA or protein synthesis and not associated with changes in the expression of bcl‐2, bax, p53, p21 or GADD45 proteins. In contrast, prolonged exposure of glioma cells to both drugs for 72 hr results in growth inhibition and apoptosis, with EC50 values around 1 μM. None of 7 glioma cell lines tested were resistant to either drug. LN‐229 cells which have partial p53‐wild‐type activity show enhanced expression of p53, p21 and bax protein, whereas bcl‐2 levels decrease, after exposure to camptothecin. In contrast, β‐lapachone increases bax protein expression in the absence of p53 activation. T98G cells are mutant for p53. In these cells, p53 levels do not change and p21 is not induced. bax accumulation in T98G cells is induced by both drugs, with bcl‐2 levels unaltered. Surprisingly, ectopic expression of murine bcl‐2 fails to abrogate the toxicity of either drug. Camptothecin, but not β‐lapachone, sensitizes human malignant glioma cells to apoptosis induced by the cytotoxic cytokines, tumor necrosis factor‐α and CD95 ligand. Thus, both drugs have potent anti‐glioma activity that may be mediated by enhanced bax expression but is not inhibited by ectopic bcl‐2 expression. Camptothecin‐like agents are particularly promising for immunochemotherapy of malignant glioma using cytotoxic drugs and CD95 ligand. Int. J. Cancer 73:707–714, 1997. © 1997 Wiley‐Liss, Inc.

Intratumor murine interleukin-12 gene therapy suppressed the growth of local and distant Ewing's sarcoma

“…Several chemotherapeutic agents have also been shown to mediate cell death via the Fas/FasL pathway. [30][31][32][33] In the present study, intratumor Ad.mIL-12 gene therapy upregulated the expression of both Fas and FasL in the treated and untreated tumors (Table 2). This upregulation was specific for IL-12 as intratumor injection of Ad.b-gal had no effect ( Figure 7, Table 2).…”

Beta-lapachone inhibits proliferation and induces apoptosis in retinoblastoma cell lines

“…[17][18][19][20][21][22] We subsequently confirmed that growth inhibition was mediated, at least in part, by induction of apoptosis, as indicated by increased caspase 3/7 activity and intranucleosomal fragmentation. In addition, beta-lapachone-treated Y79 RB cells displayed cellular morphology characteristic of apoptosis, including chromatin condensation, nuclear fragmentation with bleb formation, and pyknotic bodies 28 (http:// www.cyto.purdue.edu/cdroms/flow/vol4/index.htm).…”

“…This agent induces potent cytotoxic effects in a wide variety of malignant human cell types, including colon, lung, prostate, breast, pancreatic, ovarian, and bone cancers, as well as leukaemia, melanoma, and malignant glioma. [17][18][19][20][21][22] Beta-lapachone appears to exert a spectrum of anticancer effects, resulting in both apoptotic 20,23,24 and necrotic 17,19 cell death. Beta-lapachone can directly inhibit DNA topoisomerases I and II, 25,26 and induce G1-and/or S-phase cell-cycle delay followed by apoptosis or necrosis.…”

Mn‐SOD antisense upregulates in vivo apoptosis of squamous cell carcinoma cells by anticancer drugs and γ‐rays regulating expression of the BCL‐2 family proteins, COX‐2 and p21

“…Such a relationship was reported in p53-induced growth arrest of glioma cells. 61 Including p53 expression, additional studies are recommended to clarify the roles of Mn-SOD and ROIs in apoptosis. However, the present study revealed the importance of ROIs in apoptosis induction and suggested Mn-SOD antisense transfection as a therapeutic tool for malignancies.…”