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Oleanane triterpenoids are broad-spectrum antiproliferative and proapoptotic agents. In this study, we investigated whether reactive oxygen species (ROS) play a role in the antitumor activity of methyl-2-cyano-3, 12-dioxooleana-1, 9(11)-dien-28-oate (CDDO-Me) in OVCAR-5 and MDAH 2774 ovarian cancer cells. Treatment with CDDO-Me caused the generation of ROS (H(2)O(2)) and pre-treatment with N-acetylcysteine (NAC) prevented the generation of ROS. NAC also blocked the inhibition of cell proliferation by CDDO-Me. Likewise, NAC prevented the CDDO-Me-caused binding of fluorescein isothiocyanate (FITC)-tagged annexin V, cleavage of poly ADP-ribose polymerase-1 (PARP-1), procaspases-3, -8 and -9 and loss of mitochondrial membrane potential. CDDO-Me inhibited the expression of prosurvival phospho-AKT (p-AKT), phospho-mammalian target of rapamycin (p-mTOR) and nuclear factor-kappa B (NF-κB) (p65) signaling molecules and NF-κB-regulated antiapoptotic B-cell lymphoma-2 (BCL-2), B-cell lymphoma-extra large (BCL-xL), cellular inhibitor of apoptosis protein 1(c-IAP1) and survivin, but pre-treatment with NAC blocked the down-modulation of these signaling and antiapoptotic proteins by CDDO-Me. Together, these results indicate the pivotal role ROS play in the antiproliferative- and apoptosis-inducing activity of CDDO-Me in ovarian cancer cells; however, the role of ROS in the down-regulation of prosurvival AKT, mTOR, NF-κB and antiapoptotic BCL-2, BCL-xL, c-IAP1 and survivin warrants further investigation.

Synthetic oleanane triterpenoids are novel agents which have shown strong antitumorigenic activity against a wide range of cancer types in vitro. The objective of the present study was to determine the anticancer activity of methyl-2-cyano-3, 12-dioxooleana-1, 9(11)-dien-28-oate (CDDO-Me) derived from CDDO, a synthetic analog of oleanolic acid, and its mechanism of action in killing of human ovarian cancer cells. CDDO-Me strongly inhibited the growth of ovarian cancer cells by inducing apoptosis characterized by increased annexin V binding, cleavage of poly (ADP-ribose) polymerase (PARP-1) and procaspases-3, -8 and -9. In addition, CDDO-Me induced mitochondrial depolarization. Western blot analysis showed inhibition of prosurvival (antiapoptotic) phospho-AKT (p-AKT), nuclear factor kappa B (NF-κB) (p65) and phospho-mammalian target of rapamycin (p-mTOR) signaling proteins in cells treated with CDDO-Me. Abrogation of AKT which regulates both NF-κB and mTOR increased the sensitivity of tumor cells to CDDO-Me. Thus, these data showing strong growth-inhibitory and apoptosis-inducing activity of CDDO-Me for ovarian cancer cells through the inhibition of AKT/ NF-κB/mTOR signaling pathway provide basis for evaluation of CDDO-Me for ovarian cancer.

Promotion of apoptosis in cancer cells could potentially lead to the regression and improved prognosis of hormone-refractory prostate cancer. Xanthohumol (XN), a prenylated chalcone-derived from hops, has shown strong antitumorigenic activity towards diverse types of cancer cells. In the present study, the growth-inhibitory and apoptosis-inducing activity of XN was tested in hormone-sensitive and hormone-refractory human prostate cancer cells lines. Cell growth/viability assay (MTS) demonstrated that prostate cancer cells are highly sensitive to XN at a concentration range of 20-40 μM. The primary mode of tumor cell destruction was apoptosis as demonstrated by the binding of annexin V-FITC, cleavage of PARP-1, activation of procaspases -3, -8, and -9, mitochondrial depolarization and release of cytochrome c from mitochondria. Induction of apoptosis by XN was associated with the inhibition of prosurvival Akt, NF-κB and mTOR signaling proteins and NF-κB-regulated anti-apoptotic Bcl-2 and survivin. These studies provide a rationale for clinical evaluation of XN for the treatment of hormone-refractory metastatic prostate cancer.

Lack of apoptotic cell death has been implicated in malignant transformation and resistance to anticancer therapies. The promotion of apoptosis in cancer cells could potentially lead to the regression and improved prognosis of refractory colorectal cancer. Synthetic triterpenoids have shown strong antitumorigenic activity towards diverse cancer cell types, but have not been investigated for colorectal cancer. In the present study, we tested the apoptosis-inducing activity of oleanane triterpenoid 2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oic acid (CDDO) and its C-28 methyl ester (CDDO-Me) and C-28 imidazole (CDDO-Im) derivatives in colorectal cancer cells lines. Cell growth/viability assay (MTS) demonstrated that colorectal cancer cells are highly sensitive to CDDO-Me at concentrations of 1.25 to 10 microM. The primary mode of tumor cell destruction was apoptosis as demonstrated by the cleavage of PARP-1, activation of procaspases -3, -8, and -9 and mitochondrial depolarization. Induction of apoptosis by CDDO-Me was associated with the inhibition of pro-survival Akt, NF-kappaB and mTOR signaling proteins and NF-kappaB-regulated anti-apoptotic Bcl-2, Bcl-xL, Bad and survivin. These studies provide rationale for clinical evaluation of CDDO-Me for the treatment of advanced chemotherapy refractory colorectal cancer.

Background: Synthetic oleanolic acid triterpenoid 2-cyano-3,12-dioxooleana-, 9(11)-dien-28-oic acid (CDDO) and its methyl ester (CDDO-Me) and imidazole (CDDO-Im) derivatives exhibit potent antitumor activity against diverse types of tumor cell lines. However, the anticancer activity of these triterpenoids against prostate cancer cells has not been reported., Materials and Methods: The apoptosis-inducing activity of CDDO-Me in human prostate cancer cell lines was investigated using flow cytometry and immunoblotting., Results: Prostate cancer cells are highly sensitive to CDDO-Me at concentrations of 1.25 to 10 microM. The primary mode of tumor cell destruction was apoptosis as demonstrated by increase in annexin V-FITC binding, activation of procaspases, release of cytochrome c from mitochondria, and inhibition of anti-apoptotic proteins. Furthermore, CDDO-Me inhibited the levels of anti-apoptotic Akt, mTOR and NF-kappaB (p65) signaling molecules., Conclusion: These studies provide a rationale for clinical evaluation of CDDO-Me as adjuvant therapy for treatment of advanced and fatal form of prostate cancer.

Development of multidrug-resistance (MDR) remains a major cause of failure in the treatment of cancer with chemotherapeutic agents. In our efforts to explore alternative treatment regimens for multidrug-resistant tumors we have examined the sensitivity of MDR tumor cell lines to lymphokine activated killer (LAK) cells. Adriamycin (ADM) resistant B16-BL6 melanoma, L1210 and P388 leukemic cell lines were tested for sensitivity to lysis by LAK cells in vitro. While ADM-resistant B16-BL6 and L1210 sublines were found to exhibit at least 2-fold greater susceptibility to lysis by LAK cells, sensitivity of ADM-resistant P388 cell was similar to that of parental cells. Since ADM-resistant B16-BL6 cells were efficiently lysed by LAK cells in vitro, the efficacy of therapy with LAK cells against the ADM-resistant B16-BL6 subline in vivo was evaluated. Compared to mice bearing parental B16-BL6 tumor cells, the adoptive transfer of LAK cells and rIL2 significantly reduced formation of experimental metastases (P less than 0.009) and extended median survival time (P less than 0.001) of mice bearing ADM-resistant B16-BL6 tumor cells. Results suggest that immunotherapy with LAK cells and rIL2 may be a useful modality in the treatment of cancers with the MDR phenotype.

Earlier we have reported that the progressive growth of Lewis fibrosarcoma T241 in C57 BL/6J mice causes immunosuppression. Tumor-bearing mice were shown to possess suppressor T cells in the spleen and soluble immunosuppressive factors in the serum. The present study investigated the effect of supernatants from T241 cultures on the response of normal spleen cells to mitogens and antigens. When added to the cultures at time zero, these supernatants inhibited the proliferation responses induced with concanavalin A and phytohemagglutinin. The responses to allo-antigens in mixed lymphocyte cultures and cell-mediated lympholysis were also significantly suppressed (P less than 001). Each of these responses was suppressed in a dose-dependent manner. Predominantly associated with material possessing molecular weight of less than 10,000 daltons, the suppressive activity was completely lost by heating supernatants at 80 degrees C for 30 min. Thus, the presence of immunosuppressive materials in the culture fluids of T241 together with the occurrence of suppressor T cells and the humoral immuno-suppressive factor(s) in tumor-bearing mice are suggestive of a multifactorial mechanism whereby the growth of fibrosarcoma T241 causes immunodepression in the host.