Restoration of XAF1 expression induces apoptosis and inhibits tumor growth in gastric cancer

XAF1 (XIAP‐associated factor 1) is a novel XIAP binding protein that can antagonize XIAP and sensitize cells to other cell death triggers. Our previous results have shown that aberrant hypermethylation of the CpG sites in XAF1 promoter is strongly associated with lower expression of XAF1 in gastric cancers. In our study, we investigated the effect of restoration of XAF1 expression on growth of gastric cancers. We found that the restoration of XAF1 expression suppressed anchorage‐dependent and ‐independent growth and increased sensitivity to TRAIL and drug‐induced apoptosis. Stable cell clones expressing XAF1 exhibited delayed tumor initiation in nude mice. Restoration of XAF1 expression mediated by adenovirus vector greatly increased apoptosis in gastric cancer cell lines in a time‐ and dose‐dependent manner and sensitized cancer cells to TRAIL and drugs‐induced apoptosis. Adeno‐XAF1 transduction induced cell cycle G2/M arrest and upregulated the expression of p21 and downregulated the expression of cyclin B1 and cdc2. Notably, adeno‐XAF1 treatment significantly inhibited tumor growth, strongly enhanced the antitumor activity of TRAIL in a gastric cancer xenograft model in vivo, and significantly prolonged the survival time of animals bearing tumor xenografts. Complete eradication of established tumors was achieved on combined treatment with adeno‐XAF1 and TRAIL. Our results document that the restoration of XAF1 inhibits gastric tumorigenesis and tumor growth and that XAF1 is a promising candidate for cancer gene therapy. © 2009 UICC     

Adenovirus‐mediated expression of truncated E2F‐1 suppresses tumor growth in vitro and in vivo

BACKGROUND:

Adenovirus (Ad)‐mediated E2F‐1 gene transfer induces apoptosis in cancer cells in vitro and in vivo, but clinical application of E2F‐1 in cancer gene therapy remains controversial because of the oncogenic potential of E2F‐1. This barrier can be circumvented by using the truncated form of the E2F‐1 gene (E2Ftr) (amino acids 1 through 375), which lacks the E2F‐1 transactivation domain and cell cycle‐promoting effects.

METHODS:

The authors constructed 3 adenoviral vectors that expressed E2Ftr under regulation of the tetracycline (Tet)‐off system (AdTet‐E2Ftr1, AdTet‐E2Ftr2, and AdTet‐E2Ftr3). These vectors were compared for E2Ftr expression and apoptosis induction in cancer cells and normal cells. E2Ftr antitumor activity in vivo also was assessed in a melanoma xenograft model.

RESULTS:

One of the 3 vectors, AdTet‐E2Ftr3, had the highest E2Ftr protein expression levels, which were correlated with the greatest induction of apoptosis and inhibition of cancer cell growth. E2Ftr induced apoptosis in a variety of cancer cell lines independent of p53 status with little cytotoxicity in normal cell lines. In a mouse melanoma xenograft model, AdTet‐E2Ftr3 exhibited an approximately 80% decrease in tumor size compared with controls in vivo.

CONCLUSIONS:

The current results indicated that AdTet‐E2Ftr3 is a novel anticancer agent that has significant therapeutic activity in vitro and in vivo. Cancer 2010. © 2010 American Cancer Society.     

Gold (III) porphyrin complexes induce apoptosis and cell cycle arrest and inhibit tumor growth in colon cancer

BACKGROUND:

Gold (III) compounds have exhibited favorable antitumor properties both in vitro and in vivo. In a previous study, the authors reported that the novel gold (III) complex 1a (gold 1a) exhibited strong cytotoxicity in some tumor cell lines. In the current study, the effect of gold 1a was investigated on colon cancer cells.

METHODS:

The cytotoxicity of gold 1a was determined by using the 3‐(4,5‐dimethyl‐2‐thihazyl)‐2,5‐diphenyl‐2H‐tetrazolium bromide method. Flow cytometry was used to detect apoptosis and cell cycle. The expression of protein was evaluated by Western blot assay. Tumor growth in vivo was evaluated in nude mice.

RESULTS:

Gold 1a exhibited marked cytotoxic effects in vitro to human colon cancer, and the concentration of drug required to inhibit cell growth by 50% compared with control (IC₅₀) values ranged from 0.2 μM to 3.4 μM, which represented 8.7‐fold to 20.8‐fold greater potency than that of cisplatin. Gold 1a significantly induced apoptosis and cell cycle arrest and cleaved caspase 3, caspase 7, and poly(ADP‐ribose) polymerase; released cytochrome C, and up‐regulated p53, p21, p27, and Bax. In vivo, intraperitoneal injection of gold 1a at doses of 1.5 mg/kg and 3.0 mg/kg significantly inhibited tumor cell proliferation, induced apoptosis, and suppressed colon cancer tumor growth. An acute toxicology study indicated that gold 1a at effective antitumor concentrations did not cause any toxic side effects in mice.

CONCLUSIONS:

The current results suggested that gold 1a may be a new potential therapeutic drug for colon cancer. Cancer 2009. © 2009 American Cancer Society.     

Recurrence-free survival in prostate cancer is related to increased stromal TRAIL expression

BACKGROUND:

TRAIL (tumor necrosis factor related apoptosis‐inducing ligand) is involved in tumor immune surveillance and, thus, may be a potential cancer therapy. TRAIL expression in the tumor microenvironment has been shown to impact cancer survival in multiple tumor types, including ovarian cancer. We studied TRAIL expression and outcomes in patients with prostate cancer.

METHODS:

A tissue microarray (TMA) of 200 prostate cancer patients and benign prostate tissue controls was used to assess the epithelial and stromal protein expression of TRAIL, death receptors (DR4 and DR5), decoy receptors (DcR1 and DcR2), and the FLICE inhibitory protein (FLIP_L). We correlated these expression patterns with clinicopathological parameters and determined its impact on recurrence‐free survival.

RESULTS:

Nearly all (99.5%) prostate cancer tissues examined displayed either decreased expression of pro‐apoptotic TRAIL receptors, increased FLIP_L expression, or both. We observed elevated death receptor, decoy receptor, FLIP_L, and epithelial TRAIL expression in prostate cancer epithelium. TRAIL expression in the stromal tumor microenvironment surrounding the prostate cancer was markedly lower. Elevated TRAIL expression in the tumor microenvironment was also significantly associated with increased recurrence‐free survival (P = .014), after controlling for other prognostic markers. In contrast, epithelial expression of TRAIL did not have an effect on overall survival.

CONCLUSIONS:

Expression of the components of the pro‐apoptotic TRAIL pathway is altered in prostate cancer. Moreover, TRAIL expression in the tumor microenvironment may affect recurrence‐free survival rate of prostate cancer patients. Consequently, these results may be useful in devising future therapeutic strategies targeting the TRAIL pathway in prostate cancer. Cancer 2011. © 2010 American Cancer Society.     

Tumor suppressor XAF1 induces apoptosis,inhibits angiogenesis and inhibits tumor growth in hepatocellular carcinoma

X-linked inhibitor of apoptosis (XIAP)-associated factor 1 (XAF1), a XIAP-binding protein, is a tumor suppressor gene. XAF1 was silent or expressed lowly in most human malignant tumors. However, the role of XAF1 in hepatocellular carcinoma (HCC) remains unknown. In this study, we investigated the effect of XAF1 on tumor growth and angiogenesis in hepatocellular cancer cells. Our results showed that XAF1 expression was lower in HCC cell lines SMMC-7721, Hep G2 and BEL-7404 and liver cancer tissues than that in paired non-cancer liver tissues. Adenovirus-mediated XAF1 expression (Ad5/F35-XAF1) significantly inhibited cell proliferation and induced apoptosis in HCC cells in dose- and time- dependent manners. Infection of Ad5/F35-XAF1 induced cleavage of caspase -3, -8, -9 and PARP in HCC cells. Furthermore, Ad5/F35-XAF1 treatment significantly suppressed tumor growth in a xenograft model of liver cancer cells. Western Blot and immunohistochemistry staining showed that Ad5/F35-XAF1 treatment suppressed expression of vascular endothelial growth factor (VEGF), which is associated with tumor angiogenesis, in cancer cells and xenograft tumor tissues. Moreover, Ad5/F35-XAF1 treatment prolonged the survival of tumor-bearing mice. Our results demonstrate that XAF1 inhibits tumor growth by inducing apoptosis and inhibiting tumor angiogenesis. XAF1 may be a promising target for liver cancer treatment.     

A galectin-3 sequence polymorphism confers TRAIL sensitivity to human breast cancer cells

BACKGROUND:

A common polymorphism, rs4644, coding for Pro64 or His64 of the carbohydrate‐binding protein galectin‐3, influences the susceptibility of galectin‐3 to cleavage by matrix metalloproteinases and is associated with breast cancer incidence. Because forced expression of galectin‐3 in a galectin‐3 null breast cancer cell line confers sensitivity to tumor necrosis factor‐related apoptosis‐inducing ligand (TRAIL), the authors sought to determine whether the His64/Pro64 polymorphism of galectin‐3 affects the sensitivity to TRAIL.

METHODS:

Genomic DNA of breast cell lines was analyzed for the single nucleotide polymorphism rs4644, and cytotoxicity was determined with the MTT assay.

RESULTS:

When a collection of 9 breast cancer cell lines that express galectin‐3 was examined for lectin, galactoside‐binding, soluble, 3 (LGALS3) genotype and sensitivity to doxorubicin and TRAIL, doxorubicin sensitivity was not found to be related to LGALS3 genotype. In contrast, none of the 5 cell lines that were homozygous for Pro64 galectin‐3 were found to be sensitive to TRAIL, but 2 of 2 homozygous His64 cell lines and 1 of 2 heterozygous His64 cell lines were sensitive to TRAIL. Forced expression of galectin‐3 of defined genotype in galectin‐3 null cells was used to more directly test the effect of the Pro64His mutation on TRAIL sensitivity. High levels of expression of His64 galectin‐3 rendered BT549 cells sensitive to TRAIL and resistant to doxorubicin, but cells expressing Pro64 galectin‐3 remained resistant to TRAIL and sensitive to doxorubicin.

CONCLUSIONS:

The results of the current study indicate that the naturally occurring Pro64His mutation in galectin‐3 increases sensitivity to death receptor‐mediated apoptosis. This finding could be relevant to disparities in breast cancer outcomes across population groups, and could guide the design of future clinical trials of TRAIL‐based therapies. Cancer 2011;. © 2011 American Cancer Society.     

XAF1 as a prognostic biomarker and therapeutic target in pancreatic cancer

XAF1 (X chromosome‐linked inhibitor of apoptosis [XIAP]‐associated factor 1) is a novel XIAP modulator that negatively regulates the anti‐apoptotic effects of XIAP and sensitizes cells to other cell death triggers. It has been reported to be downregulated in a variety of human cancer cell lines. However, the role of XAF1 in pancreatic carcinogenesis remains unclear. In the present study, we investigated the prognostic values of XAF1 expression and its regulation in cancer cell growth and apoptosis both in vitro and in vivo. From the immunohistochemistry staining of tissue microarray, 40 of 89 (44.9%) pancreatic specimens showed low levels of XAF1 expression. Statistical analysis suggested the downregulation of XAF1 was significantly correlated with tumor staging (P = 0.047) and those patients with low XAF1 levels had shorter survival times (P = 0.0162). Multivariate analysis indicated that XAF1 expression was an independent prognostic indicator of the survival of patients with pancreatic cancer (P = 0.007). Furthermore, we found that restoration of XAF1 expression mediated by Ad5/F35 virus suppressed cell proliferation and induced cell cycle arrest and apoptosis, accompanied by the activation of caspases 3, 8, and 9 and poly(ADP‐ribose) polymerase as well as increased level of cytochrome c and Bid cleavage. Notably, XAF1 restoration robustly decreased survivin expression rather than XIAP. In addition, in vivo s.c. xenografts from Ad5/F35‐XAF1 treatment, which showed less cellular proliferation and enhanced apoptosis, were significantly smaller than those from control groups. Our findings document that XAF1 is a valuable prognostic marker in pancreatic cancer and could be a potential candidate for cancer gene therapy. (Cancer Sci 2009)     

Putative tumor suppressor miR‐145 inhibits colon cancer cell growth by targeting oncogene friend leukemia virus integration 1 gene

BACKGROUND:

Tumor suppressor microRNA miR‐145 is commonly down‐regulated in colon carcinoma tissues, but its specific role in tumors remains unknown.

METHODS:

In this study, the authors identified the Friend leukemia virus integration 1 gene (FLI1) as a novel target of miR‐145. FLI1 is involved in t(11;22)(q24:q12) reciprocal chromosomal translocation in Ewing sarcoma, and its expression appears to be associated with biologically more aggressive tumors.

RESULTS:

The authors demonstrated that miR‐145 targets a putative microRNA regulatory element in the 3′‐untranslated region (UTR) of FLI1, and its abundance is reversely associated with FLI1 expression in colon cancer tissues and cell lines. By using a luciferase/FLI1 3′‐UTR reporter system, they found that miR‐145 down‐regulated the reporter activity, and this down‐regulation was reversed by anti–miR‐145. Mutation of the miR‐145 microRNA regulatory element sequence in the FLI1 3′‐UTR abolished the activity of miR‐145. miR‐145 decreased FLI1 protein but not FLI1 mRNA, suggesting a mechanism of translational regulation. Furthermore, the authors demonstrated that miR‐145 inhibited cell proliferation and sensitized LS174T cells to 5‐fluorouracil–induced apoptosis.

CONCLUSIONS:

Taken together, these results suggest that miR‐145 functions as a tumor suppressor by down‐regulating oncogenic FLI1 in colon cancer. Cancer 2011. © 2010 American Cancer Society.     

The XAF1 tumor suppressor induces autophagic cell death via upregulation of Beclin-1 and inhibition of Akt pathway

Autophagy is designated as type II programmed cell death and may confer a tumor-suppressive function. Our previous studies have shown that XIAP-associated factor 1 (XAF1) induced apoptosis and inhibited tumor growth in gastric cancer cells. In this study, we investigated the effect of XAF1 on the induction of autophagy in gastric cancer cells. We found that adenovirus vector-mediated XAF1 (adeno-XAF1) expression markedly induced autophagy, upregulated the level of Beclin-1 and inhibited phospho-Akt and phospho-p70S6K in gastric cancer cells. The downregulation of Beclin 1 or 3-methyladenine treatment suppressed adeno-XAF1-induced autophagy, but significantly enhanced adeno-XAF1-induced apoptosis. A pan-caspase inhibitor prevented adeno-XAF1-induced apoptosis, but significantly increased adeno-XAF1-induced autophagy. Furthermore, adeno-XAF1 induced autophagy in xenograft tumor and inhibited tumor growth. Our results document that adeno-XAF1 induces autophagy through upregulation of Beclin 1 expression and inhibition of Akt/p70S6K pathway, and reveal a new mechanism of XAF1 tumor suppression.     

Loss of SM22 is a characteristic signature of colon carcinogenesis and its restoration suppresses colon tumorigenicity in vivo and in vitro

BACKGROUND:

We previously found the down‐expression of SM22 in an experimental animal model of colorectal cancer by performing a proteomic analysis. In this study, we addressed the expression and molecular mechanisms of SM22 in human colorectal cancer.

METHODS:

To evaluate the expression of SM22 in colon cancers, Western blot and immunohistochemistry were performed in 13 normal, 14 adenomas, and 44 adenocarcinomas. To address the role of SM22 in colon carcinogenesis, SM22 was restored in the colon cancer cells by the transfection with the pIRES2 vector containing full‐length SM22 cDNA and tested for tumorigenicity in vivo and in vitro.

RESULTS:

SM22 was found to be significantly down‐regulated in adenocarcinoma (58%) compared with adenoma (21.4%) and normal (15.3%). The loss of SM22 correlated with poor differentiation of tumor (P = 0.009) and lymph node metastasis (P = 0.029). Restoration of SM22 expression inhibited cell migration, colony‐forming ability of cancer cells, and induced retardation of in vivo tumor growth in a xenograft model.

CONCLUSIONS:

Loss of SM22 is a molecular signature of colon cancer and is closely associated with progression, differentiation, and metastasis of colon cancer. The restoration of SM22 leads to an inhibition of colon carcinogenesis in vivo and in vitro, suggesting that SM22 might potentially function as a novel tumor suppressor. Cancer 2010. © 2010 American Cancer Society.     

Dasatinib induces autophagic cell death in human ovarian cancer

BACKGROUND:

Dasatinib, an inhibitor of Src/Abl family kinases, can inhibit tumor growth of several solid tumors. However, the effect and mechanism of action of dasatinib in human ovarian cancer cells remains unknown.

METHODS:

Dasatinib‐induced autophagy was determined by acridine orange staining, punctate localization of GFP‐LC3, LC3 protein blotting, and electron microscopy. Significance of beclin 1, AKT, and Bcl‐2 in dasatinib‐induced autophagy and growth inhibition was assayed by small interfering RNA (siRNA) silencing and/or overexpression of the gene of interest.

RESULTS:

Dasatinib inhibited cell growth by inducing little apoptosis, but substantial autophagy in SKOv3 and HEY ovarian cancer cells. In vivo studies showed dasatinib inhibited tumor growth and induced both autophagy and apoptosis in a HEY xenograft model. Knockdown of beclin 1 and Atg12 expression with their respective siRNAs diminished dasatinib‐induced autophagy, whereas knockdown of p27Kip1 with specific siRNAs did not. Small hairpin RNA knockdown of beclin 1 expression reduced dasatinib‐induced autophagy and growth inhibition. Dasatinib reduced the phosphorylation of AKT, mTOR, p70S6K, and S6 kinase expression. Constitutive expression of AKT1 and AKT2 inhibited dasatinib‐induced autophagy in both HEY and SKOv3 cells. Dasatinib also reduced Bcl‐2 expression and activity. Overexpression of Bcl‐2 partially prevented dasatinib‐induced autophagy.

CONCLUSIONS:

Dasatinib induces autophagic cell death in ovarian cancer that partially depends on beclin 1, AKT, and Bcl‐2. These results may have implications for clinical use of dasatinib. Cancer 2010. © 2010 American Cancer Society.     

Flavokawain B,a kava chalcone,induces apoptosis via up‐regulation of death‐receptor 5 and Bim expression in androgen receptor negative,hormonal refractory prostate cancer cell lines and reduces tumor growth

Limited success has been achieved in extending the survival of patients with metastatic and hormone‐refractory prostate cancer (HRPC). There is a strong need for novel agents in the treatment and prevention of HRPC. We have shown that flavokawain B (FKB), a kava chalcone, is about 4‐ to 12‐fold more effective in reducing the cell viabilities of androgen receptor (AR)‐negative, HRPC cell lines DU145 and PC‐3 than AR‐positive, hormone‐sensitive prostate cancer cell lines LAPC4 and LNCaP, with minimal effect on normal prostatic epithelial and stromal cells. FKB induces apoptosis with an associated increased expression of proapoptotic proteins: death receptor‐5, Bim and Puma and a decreased expression of inhibitors of apoptosis protein: XIAP and survivin. Among them, Bim expression was significantly induced by FKB as early as 4 hr of the treatment. Knockdown of Bim expression by short‐hairpin RNAs attenuates the inhibitory effect on anchorage‐dependent and ‐independent growth and caspase cleavages induced by FKB. These findings suggest that the effect of FKB, at least in part, requires Bim expression. In addition, FKB synergizes with TRAIL for markedly enhanced induction of apoptosis. Furthermore, FKB treatment of mice bearing DU145 xenograft tumors results in tumor growth inhibition and increases Bim expression in tumor tissues. Together, these results suggest robust mechanisms for FKB induction of apoptosis preferentially for HRPC and the potential usefulness of FKB for prevention and treatment of HRPC in an adjuvant setting.     

Loss of XIAP sensitizes rosiglitazone-induced growth inhibition of colon cancer in vivo

Ligands for peroxisome proliferator-activated receptor gamma (PPAR gamma) possess anticancer properties. However, the efficacy of PPAR gamma ligands varies in different cancers. In colon cancer, the role of PPAR gamma and its ligands is controversial. We recently showed that downregulation of X-linked inhibitor of apoptosis protein (XIAP) could sensitize colon cancer cells to troglitazone, and 15-deoxy-D12,14-prostaglandin J2 (15-PGJ2) induced cell killing. In our study, we aimed to examine whether rosiglitazone, another more clinically relevant PPAR gamma ligand, has any synergistic anticancer effect with XIAP downregulation in colon cancer. Human colon cancer cell lines HCT116-XIAP(+/+) cells and HCT116-XIAP(-/-) cells were treated with various concentrations of rosiglitazone. The effects of rosiglitazone on cell proliferation, apoptosis and growth of xenograft colon cancers were studied. Rosiglitazone barely suppressed the growth and only very weakly induced apoptosis in HCT116 cells in vitro. Loss of XIAP did not sensitize HCT116 cells to rosiglitazone-induced growth inhibition or apoptosis. In vivo studies revealed that rosiglitazone strongly suppressed the growth of xenograft colon cancer, especially tumors derived from HCT116-XIAP(-/-) cells. The rosiglitazone-treated tumor had reduced expression of ki-67 and lowered mitotic rate. Downregulation of XIAP was associated with an impaired activation of PPAR gamma by its ligand. Rosiglitazone induced marked upregulation of PTEN in HCT116-XIAP(-/-) cells, as well as in xenograft tumors derived from HCT116-XIAP(-/-) cells. We concluded that rosiglitazone significantly suppresses the growth of xenograft colon cancer, and downregulation of XIAP sensitizes the xenograft tumors to rosiglitazone-induced tumor suppression in vivo via upregulation of PTEN.     

CD66c is a novel marker for colorectal cancer stem cell isolation,and its silencing halts tumor growth in vivo

BACKGROUND:

Despite the well recognized expression of the cell surface markers cluster of differentiation 44 (homing cell adhesion molecule) and CD133 (Prominin 1) on human colorectal cancer stem cells (CCSCs), these molecules do not appear to be effective targets for stem cell‐directed therapies. Because the surface marker CD66c (also known as carcinoembryonic antigen‐related cell adhesion molecule 6) has demonstrated promise as a therapeutic target in pancreatic malignancy, the authors evaluated its potential as a target for stem cell‐directed treatment of colorectal cancer.

METHODS:

First, the authors characterized CD66c expression by flow cytometry and immunohistochemistry in colon cancer samples and in normal colon tissues. Then, the coexpression of CD66c and CD133 was evaluated on putative CCSCs. CD66c expression also was measured in stem cell‐enriched colon spheres. Finally, the effects of small‐interfering RNA‐mediated CD66c silencing on the in vitro and in vivo growth of Caco2 colon cancer cells were evaluated.

RESULTS:

CD66c expression was significantly higher in colon cancers than in contiguous normal colon tissues and paralleled cancer stage. CD66c was absent in CD133‐positive cells that were isolated from normal colon, whereas its expression was brightest (CD66c^bright) in CD133‐positive cells from colon cancer samples. In vitro experiments demonstrated that colon spheres were considerably enriched in a CD66c^bright population in a fashion comparable to the enrichment observed in fresh liver metastases. In vitro proliferation and clonogenic potential were hampered when CD66c was silenced in Caco2 cells. Finally, in vivo xenograft experiments demonstrated that CD66c silencing almost completely abrogated the tumorigenic potential of Caco2 cells.

CONCLUSIONS:

CD66c^bright expression was associated with colon cancer stem cells and CD66c silencing blocked tumor growth, thereby opening the way to a potential new treatment for colon cancer. Cancer 2013. © 2012 American Cancer Society.     

Novel targets for sensitizing breast cancer cells to TRAIL‐induced apoptosis with siRNA delivery

Tumor necrosis factor‐related apoptosis‐inducing ligand (TRAIL) induces apoptosis in variety of cancer cells without affecting most normal cells, which makes it a promising agent for cancer therapy. However, TRAIL therapy is clinically not effective due to resistance induction. To identify novel regulators of TRAIL that can aid in therapy, protein targets whose silencing sensitized breast cancer cells against TRAIL were screened with an siRNA library against 446 human apoptosis‐related proteins in MDA‐231 cells. Using a cationic lipopolymer (PEI‐αLA) for delivery of library members, 16 siRNAs were identified that sensitized the TRAIL‐induced death in MDA‐231 cells. The siRNAs targeting BCL2L12 and SOD1 were further evaluated based on the novelty and their ability to sensitize TRAIL induced cell death. Silencing both targets sensitized TRAIL‐mediated cell death in MDA‐231 cells as well as TRAIL resistant breast cancer cells, MCF‐7. Combination of TRAIL and siRNA silencing BCL2L12 had no effect in normal human umbilical vein cells and human bone marrow stromal cell. The silencing of BCL2L12 and SOD1 enhanced TRAIL‐mediated apoptosis in MDA‐231 cells via synergistically activating capsase‐3 activity. Hence, here we report siRNAs targeting BCL2L12 and SOD1 as a novel regulator of TRAIL‐induced cell death in breast cancer cells, providing a new approach for enhancing TRAIL therapy for breast cancer. The combination of siRNA targeting BCL2L12 and TRAIL can be a highly effective synergistic pair in breast cancer cells with minimal effect on the non‐transformed cells.     

Combining TRAIL with PI3 Kinase or HSP90 inhibitors enhances apoptosis in colorectal cancer cells via suppression of survival signaling

TRAIL has been shown to induce apoptosis in cancer cells, but in some cases they fail to respond to this ligand. We explored the ability of representative phosphatidylinositol-3-kinase (PI3 Kinase)/mTOR and HSP90 inhibitors to overcome TRAIL resistance by increasing apoptosis in colorectal cancer models. We determined the sensitivity of 27 human colorectal cancer and 2 non-transformed colon epithelial cell lines to TRAIL treatment. A subset of the cancer cell lines with a range of responses to TRAIL was selected from the panel for treatment with TRAIL combined with the PI3 Kinase/mTOR inhibitor PI-103 or the HSP90 inhibitor 17-AAG (tanespimycin). Two TRAIL-resistant cell lines were selected for in vivo combination studies with TRAIL and 17-AAG. We found that 13 colorectal cancer cell lines and the 2 non-transformed colon epithelial cell lines were resistant to TRAIL. We demonstrated that co-treatment of TRAIL and PI-103 or 17-AAG was synergistic or additive and significantly enhanced apoptosis in colorectal cancer cells. This was associated with decreased expression or activity of survival protein biomarkers such as ERBB2, AKT, IKKα and XIAP. In contrast, the effect of the combination treatments in non-transformed colon cells was minimal. We show here for the first time that co-treatment in vivo with TRAIL and 17-AAG in two TRAIL-resistant human colorectal cancer xenograft models resulted in significantly greater tumor growth inhibition compared to single treatments. We propose that combining TRAIL with PI3 Kinase/mTOR or HSP90 inhibitors has therapeutic potential in the treatment of TRAIL-resistant colorectal cancers.     

NV‐128, a novel isoflavone derivative,induces caspase‐independent cell death through the Akt/mammalian target of rapamycin pathway

BACKGROUND:

Resistance to apoptosis is 1 of the key events that confer chemoresistance and is mediated by the overexpression of antiapoptotic proteins, which inhibit caspase activation. The objective of this study was to evaluate whether the activation of an alternative, caspase‐independent cell death pathway could promote death in chemoresistant ovarian cancer cells. The authors report the characterization of NV‐128 as an inducer of cell death through a caspase‐independent pathway.

METHODS:

Primary cultures of epithelial ovarian cancer (EOC) cells were treated with increasing concentration of NV‐128, and the concentration that caused 50% growth inhibition (GI₅₀) was determined using a proprietary assay. Apoptotic proteins were characterized by Western blot analyses, assays that measured caspase activity, immunohistochemistry, and flow cytometry. Protein‐protein interactions were determined using immunoprecipitation. In vivo activity was measured in a xenograft mice model.

RESULTS:

NV‐128 was able to induce significant cell death in both paclitaxel‐resistant and carboplatin‐resistant EOC cells with a GI₅₀ between 1 μg/mL and 5 μg/mL. Cell death was characterized by chromatin condensation but was caspase‐independent. The activated pathway involved the down‐regulation of phosphorylated AKT, phosphorylated mammalian target of rapamycin (mTOR), and phosphorylated ribosomal p70 S6 kinase, and the mitochondrial translocation of beclin‐1 followed by nuclear translocation of endonuclease G.

CONCLUSIONS:

The authors characterized a novel compound, NV‐128, which inhibits mTOR and promotes caspase‐independent cell death. The current results indicated that inhibition of mTOR may represent a relevant pathway for the induction of cell death in cells resistant to the classic caspase‐dependent apoptosis. These findings demonstrate the possibility of using therapeutic drugs, such as NV‐128, which may have beneficial effects in patients with chemoresistant ovarian cancer. Cancer 2009. © 2009 American Cancer Society.