RLIP76 in defense of radiation poisoning.

Purpose: To determine the role of RLIP76 in providing protection from radiation and chemotherapy. In the present report, we used RLIP76 to refer to both the mouse (Ralbp1) and the human (RLIP76) 76-kDa splice variant proteins (RLIP76) for convenience and to avoid confusion. In other reports, Ralbp1 refers to the mouse enzyme (encoded by the Ralbp1 gene), which is structurally and functionally homologous to RLIP76, the human protein encoded by the human RALBP1 gene.

Mitogen-activated protein kinase kinase 1/2 inhibitors and 17-allylamino-17-demethoxygeldanamycin synergize to kill human gastrointestinal tumor cells in vitro via suppression of c-FLIP-s levels and activation of CD95.

Prior studies have noted that inhibitors of mitogen-activated protein kinase (MAPK) kinase 1/2 (MEK1/2) enhanced geldanamycin lethality in malignant hematopoietic cells by promoting mitochondrial dysfunction. The present studies focused on defining the mechanism(s) by which these agents altered survival in carcinoma cells. MEK1/2 inhibitors [PD184352; AZD6244 (ARRY-142886)] interacted in a synergistic manner with geldanamycins [17-allylamino-17-demethoxygeldanamycin (17AAG) and 17-dimethylaminoethylamino-17-demethoxy-geldanamycin] to kill hepatoma and pancreatic carcinoma cells that correlated with inactivation of extracellular signal-regulated kinase 1/2 and AKT and with activation of p38 MAPK; p38 MAPK activation was reactive oxygen species dependent.

Vorinostat and sorafenib increase ER stress, autophagy and apoptosis via ceramide-dependent CD95 and PERK activation.

We recently noted that low doses of sorafenib and vorinostat interact in a synergistic fashion to kill carcinoma cells by activating CD95, and this drug combination is entering phase I trials. The present studies mechanistically extended our initial observations. Low doses of sorafenib and vorinostat, but not the individual agents, caused an acidic sphingomyelinase and fumonisin B1-dependent increase in CD95 surface levels and CD95 association with caspase 8.

Mechanism of in vitro pancreatic cancer cell growth inhibition by melanoma differentiation-associated gene-7/interleukin-24 and perillyl alcohol.

The death rate for pancreatic cancer approximates the number of new cases each year, and when diagnosed, current therapeutic regimens provide little benefit in extending patient survival. These dire statistics necessitate the development of enhanced single or combinatorial therapies to decrease the pathogenesis of this invariably fatal disease. Melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24) is a potent cancer gene therapeutic because of its broad-spectrum cancer-specific apoptosis-inducing properties as well as its multipronged indirect antitumor activities.

Vorinostat and sorafenib synergistically kill tumor cells via FLIP suppression and CD95 activation.

Purpose And Design: Mechanism(s) by which the multikinase inhibitor sorafenib and the histone deacetylase inhibitor vorinostat interact to kill hepatic, renal, and pancreatic adenocarcinoma cells has been defined.

Results: Low doses of sorafenib and vorinostat interacted in vitro in a synergistic fashion to kill hepatic, renal, and pancreatic adenocarcinoma cells in multiple short-term viability (24-96 h) and in long-term colony formation assays. Cell killing was suppressed by inhibition of cathepsin proteases and caspase-8 and, to a lesser extent, by inhibition of caspase-9.

Characterization of infectivity of knob-modified adenoviral vectors in glioma.

Malignant glioma continues to be a major target for gene therapy and virotherapy due to its aggressive growth and the current lack of effective treatment. However, these approaches have been hampered by inefficient infection of glioma cells by viral vectors,particularly vectors derived from serotype 5 adenoviruses (Ad5). This results from limited cell surface expression of the primary adenovirus receptor, coxsackie-adenovirus-receptor (CAR), on tumor cells.

Regulation of autophagy by ceramide-CD95-PERK signaling.

The manuscripts by Park et al. and Zhang et al. were initially planned as studies to understand the regulation of cell survival in transformed cells treated with sorafenib and vorinostat, and in primary hepatocytes treated with a bile acid+MEK1/2 inhibitor.

Searching for a cure: gene therapy for glioblastoma.

Glioblastoma multiforme (GBM) is an invariably fatal malignancy. The lethality of GBM has been linked to the highly invasive nature of GBM cells, their escape from immune cell oversight and their high degree of resistance to multiple established therapeutic modalities. The resistance of GBM cells to undergo death processes has, in part, been associated with mutations of specific oncogenes and altered expression of other signaling molecules that lead to reduced capacities to activate multiple apoptosis pathways as well as altered rates of DNA repair and autophagy in response to cytotoxic drugs and cellular stresses.

Chemoprevention by perillyl alcohol coupled with viral gene therapy reduces pancreatic cancer pathogenesis.

Pancreatic cancer is one of the deadliest of cancers. Even with aggressive therapy, the 5-year survival rate is <5%, mandating development of more effective treatments. Melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24) shows potent antitumor activity against most cancers displaying safety with significant clinical efficacy.

Interruption of the Ras/MEK/ERK signaling cascade enhances Chk1 inhibitor-induced DNA damage in vitro and in vivo in human multiple myeloma cells.

The role of the Ras/MEK/ERK pathway was examined in relation to DNA damage in human multiple myeloma (MM) cells exposed to Chk1 inhibitors in vitro and in vivo. Exposure of various MM cells to marginally toxic concentrations of the Chk1 inhibitors UCN-01 or Chk1i modestly induced DNA damage, accompanied by Ras and ERK1/2 activation. Interruption of these events by pharmacologic (eg, the farnesyltransferase inhibitor R115777 or the MEK1/2 inhibitor PD184352) or genetic (eg, transfection with dominant-negative Ras or MEK1 shRNA) means induced pronounced DNA damage, reflected by increased gammaH2A.

Multiple cyclin kinase inhibitors promote bile acid-induced apoptosis and autophagy in primary hepatocytes via p53-CD95-dependent signaling.

Previously, using primary hepatocytes residing in early G1 phase, we demonstrated that expression of the cyclin-dependent kinase (CDK) inhibitor protein p21Cip-1/WAF1/mda6 (p21) enhanced the toxicity of deoxycholic acid (DCA) + MEK1/2 inhibitor. This study examined the mechanisms regulating this apoptotic process. Overexpression of p21 or p27(Kip-1) (p27) enhanced DCA + MEK1/2 inhibitor toxicity in primary hepatocytes that was dependent on expression of acidic sphingomyelinase and CD95.

Autocrine regulation of mda-7/IL-24 mediates cancer-specific apoptosis.

A noteworthy aspect of melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24) as a cancer therapeutic is its ability to selectively kill cancer cells without harming normal cells. Intracellular MDA-7/IL-24 protein, generated from an adenovirus expressing mda-7/IL-24 (Ad.mda-7), induces cancer-specific apoptosis by inducing an endoplasmic reticulum (ER) stress response.

Lapatinib resistance in HCT116 cells is mediated by elevated MCL-1 expression and decreased BAK activation and not by ERBB receptor kinase mutation.

We have defined some of the mechanisms by which the kinase inhibitor lapatinib kills HCT116 cells. Lapatinib inhibited radiation-induced activation of ERBB1/2, extracellular signal-regulated kinases 1/2, and AKT, and radiosensitized HCT116 cells. Prolonged incubation of HCT116 cells with lapatinib caused cell killing followed by outgrowth of lapatinib-adapted cells.

A fiber-modified mesothelin promoter-based conditionally replicating adenovirus for treatment of ovarian cancer.

Purpose: Recently, virotherapy has been proposed as a new therapeutic approach for ovarian cancer. Conditionally replicative adenoviruses (CRAd) may contain tumor-specific promoters that restrict virus replication to cancer cells. Mesothelin, a cell surface glycoprotein, is overexpressed in ovarian cancer but not in normal ovarian tissues.

Vorinostat synergistically potentiates MK-0457 lethality in chronic myelogenous leukemia cells sensitive and resistant to imatinib mesylate.

Interactions between the dual Bcr/Abl and aurora kinase inhibitor MK-0457 and the histone deacetylase inhibitor vorinostat were examined in Bcr/Abl(+) leukemia cells, including those resistant to imatinib mesylate (IM), particularly those with the T315I mutation. Coadministration of vorinostat dramatically increased MK-0457 lethality in K562 and LAMA84 cells. Notably, the MK-0457/vorinostat regimen was highly active against primary CD34(+) chronic myelogenous leukemia (CML) cells and Ba/F3 cells bearing various Bcr/Abl mutations (ie, T315I, E255K, and M351T), as well as IM-resistant K562 cells exhibiting Bcr/Abl-independent, Lyn-dependent resistance.

Human chorionic gonadotropin (hCG) interacts with lovastatin and ionizing radiation to modulate prostate cancer cell viability in vivo.

The ability of human chorionic gonadotropin (hCG) to modify prostate carcinoma viability in vitro and in vivo when combined with the HMG CoA reductase inhibitor lovastatin and ionizing radiation was investigated. Treatment of PC-3 cells in vitro with hCG caused a modest increase in numbers of non-viable cells within 96 h. Treatment of cells with hCG followed by exposure to the HMG CoA reductase inhibitor lovastatin suppressed AKT phosphorylation and enhanced the cytotoxic effects of hCG.

MDA-7/IL-24 plus radiation enhance survival in animals with intracranial primary human GBM tumors.

Melanoma differentiation associated gene-7/interleukin 24 (mda-7/IL-24) is a cytokine displaying selective apoptosis-inducing activity in tumors, including glioblastoma (GBM), without damaging normal cells. The present studies focused on defining whether an adenovirus expressing MDA-7/IL-24, Ad.mda-7, infused into pre-formed invasive primary human GBM tumors growing in athymic mouse brains altered tumor cell growth and animal survival, and whether Ad.

Transcriptional and post-transcriptional mechanisms for lysophosphatidic acid-induced cyclooxygenase-2 expression in ovarian cancer cells.

Emerging evidence suggests that lysophosphatidic acid (LPA) is a physiological regulator of cyclooxygenase-2 (Cox-2) expression. Herein we used ovarian cancer cells as a model to investigate the molecular mechanisms that link the LPA G protein-coupled receptors (GPCRs) to Cox-2 expression. LPA stimulated Cox-2 expression and release of prostaglandins though the LPA(1), LPA(2), and LPA(5) receptors.

Transient exposure of carcinoma cells to RAS/MEK inhibitors and UCN-01 causes cell death in vitro and in vivo.

The present studies were initiated to determine in greater molecular detail how MEK1/2 inhibitors [PD184352 and AZD6244 (ARRY-142886)] interact with UCN-01 (7-hydroxystaurosporine) to kill mammary carcinoma cells in vitro and radiosensitize mammary tumors in vitro and in vivo and whether farnesyl transferase inhibitors interact with UCN-01 to kill mammary carcinoma cells in vitro and in vivo. Expression of constitutively activated MEK1 EE or molecular suppression of JNK and p38 pathway signaling blocked MEK1/2 inhibitor and UCN-01 lethality, effects dependent on the expression of BAX, BAK, and, to a lesser extent, BIM and BID. In vitro colony formation studies showed that UCN-01 interacted synergistically with the MEK1/2 inhibitors PD184352 or AZD6244 and the farnesyl transferase inhibitors FTI277 and R115,777 to kill human mammary carcinoma cells.

A cancer terminator virus eradicates both primary and distant human melanomas.

The prognosis and response to conventional therapies of malignant melanoma inversely correlate with disease progression. With increasing thickness, melanomas acquire metastatic potential and become inherently resistant to radiotherapy and chemotherapy. These harsh realities mandate the design of improved therapeutic modalities, especially those targeting metastases.

PERK-dependent regulation of MDA-7/IL-24-induced autophagy in primary human glioma cells.

Melanoma differentiation associated gene-7/interleukin 24 (mda-7/IL-24) is a novel cytokine displaying selective apoptosis-inducing activity in transformed cells without harming normal cells. The studies by Yacoub et al. (Mol Cancer Ther 2008; 7:314-29) further defines the mechanism(s) by which a GST-MDA-7 fusion protein inhibits cell survival of primary human glioma cells in vitro.

Regulation of GST-MDA-7 toxicity in human glioblastoma cells by ERBB1, ERK1/2, PI3K, and JNK1-3 pathway signaling.

The present studies defined the biological effects of a GST fusion protein of melanoma differentiation-associated gene-7 (mda-7), GST-MDA-7 (1 and 30 nmol/L), on cell survival and cell signaling in primary human glioma cells in vitro. GST-MDA-7, in a dose- and time-dependent fashion killed glioma cells with diverse genetic characteristics; 1 nmol/L caused arrest without death, whereas 30 nmol/L caused arrest and killing after exposure. Combined inhibition of extracellular signal-regulated kinase 1/2 (ERK1/2) and AKT function was required to enhance 1 nmol/L GST-MDA-7 lethality in all cell types, whereas combined activation of MEK1 and AKT was required to suppress 30 nmol/L GST-MDA-7 lethality; both effects are mediated in part by modulating c-Jun NH(2)-terminal kinase (JNK) 1-3 activity.

Acquired and innate resistance to the cancer-specific apoptosis-inducing cytokine, mda-7/IL-24: not insurmountable therapeutic problems.

Despite significant progress in early cancer detection and aggressive therapies, effective treatments for metastatic disease frequently fall short of producing the desired effect of engendering a 'cure.' This can be attributed in part to inherent and acquired resistance of primary and evolving tumor cells to conventional therapeutic approaches. Agents that can interfere with critical aberrant cell signaling and survival pathways in tumor cells while displaying minimal or preferably no toxicity to normal cells represent potentially powerful tools for cancer therapy.

Targeted combinatorial therapy of non-small cell lung carcinoma using a GST-fusion protein of full-length or truncated MDA-7/IL-24 with Tarceva.

Melanoma differentiation associated gene-7/interleukin-24 (mda-7/IL-24), a cytokine belonging to the IL-10 family, displays cancer-specific apoptosis-inducing properties when delivered by a replication-incompetent adenovirus (Ad.mda-7) or as a GST-tagged recombinant protein (GST-MDA-7). Previous studies demonstrated that an adenovirus expressing M4, a truncated version of MDA-7/IL-24 containing amino acid residues 104-206, also induced similar cancer-specific apoptosis.