RABL6A promotes G1-S phase progression and pancreatic neuroendocrine tumor cell proliferation in an Rb1-dependent manner.

Mechanisms of neuroendocrine tumor (NET) proliferation are poorly understood, and therapies that effectively control NET progression and metastatic disease are limited. We found amplification of a putative oncogene, RABL6A, in primary human pancreatic NETs (PNET) that correlated with high-level RABL6A protein expression. Consistent with those results, stable silencing of RABL6A in cultured BON-1 PNET cells revealed that it is essential for their proliferation and survival.

Caspase-2-Based Regulation of the Androgen Receptor and Cell Cycle in the Prostate Cancer Cell Line LNCaP.

Caspase-2 can induce apoptosis in response to extrinsic and intrinsic signals. Unlike other caspases, this protein is not expressed solely in nonnuclear compartments; a subpopulation is constitutively localized in the nucleus. As one of the most evolutionarily conserved caspases, caspase-2 may have roles in multiple cellular processes.

Mechanisms of ascorbate-induced cytotoxicity in pancreatic cancer.

Purpose: Pharmacologic concentrations of ascorbate may be effective in cancer therapeutics. We hypothesized that ascorbate concentrations achievable with i.v.

KN-93 inhibits androgen receptor activity and induces cell death irrespective of p53 and Akt status in prostate cancer.

It has been suggested that the downregulation of AR expression should be considered the principal strategy for the treatment of hormone-refractory prostate cancer. We have previously shown that inhibition of AR induced PI3K-independent activation of Akt that was mediated by CaMKII. In this study, we found that the CaMKII inhibitor KN-93 has a broader effect on apoptosis than just inhibition of CaMKII: first, KN-93 inhibits AR activity and induces cell death in PCa cells after androgen deprivation when many other drugs fail to kill prostate cancer cells; second, KN-93 inhibits expression of the anti-apoptotic protein Mcl-1 and induces expression of the pro-apoptotic protein PUMA; third, KN-93-mediated cell death is p53-independent; and fourth, KN-93 induces the generation of ROS.

MicroRNA-34 mediates AR-dependent p53-induced apoptosis in prostate cancer.

We investigated whether knocking down AR expression effects apoptosis after treatment with different apoptosis-inducing agents. We found that siRNA AR (si-AR) significantly decreased apoptosis induced by topoisomerase inhibitors doxorubicin (DOX) and camptothecin (Campt). It is known that DNA double-strand break inducing agents leads to activation (phosphorylation) of p53 that in turn regulates the expression of a variety of apoptosis-related genes including microRNA(miR)-34a and 34b/c.

Unique resistance of breast carcinoma cell line T47D to TRAIL but not anti-Fas is linked to p43cFLIP(L).

The majority of breast cancer cell lines are resistant to tumor necrosis factor -related apoptosis inducing ligand (TRAIL) induced apoptosis. TRAIL and Fas receptor death-inducing signaling complex (DISCs) formation are similar and involve ligand-dependent recruitment of FADD and caspase-8. We have found that the breast carcinoma cell line T47D is an unusual example of selective sensitivity to anti-Fas mAb treatment but resistant to TRAIL.

Calcium/calmodulin-dependent kinase II plays an important role in prostate cancer cell survival.

It has recently been shown that the androgen receptor (AR) is the main factor that required for prostate cancer cells survival. We show that knocking down AR expression by siRNA induces PI3K-independent activation of Akt, which was mediated by calcium/calmodulin-dependent kinase II (CaMKII). We further show, for the first time, that prostate cancer cells express beta,gamma and delta CaMKII genes, and the expression of these genes is under the control of AR activity: active AR in the presence of androgens inhibits CaMKII gene expression whereas inhibition of AR activity results in elevated level of kinase activity and in enhanced expression of CaMKII-beta and -gamma genes.

TSA-induced cell death in prostate cancer cell lines is caspase-2 dependent and involves the PIDDosome.

The histone deacetylase inhibitor Trichostatin A (TSA) has previously been found to induce caspase activity in the human prostate cancer cell lines DU145 and LNCaP. TSA treatment resulted in the release of cytochrome c and Smac/DIABLO from mitochondria in DU145, and activation of caspase-9 in both cell lines. We concluded that TSA mediated its effect via the mitochondrial pathway.

Mechanisms of cell death induced by histone deacetylase inhibitors in androgen receptor-positive prostate cancer cells.

Histone deacetylase inhibitors (HDACI) are potential therapeutic agents that inhibit tumor cell growth and survival. Although there are several publications regarding the effects of HDACIs on prostate cancer cell growth, their mechanism(s) of action remains undefined. We treated several human prostate cancer cell lines with the HDACI trichostatin A and found that trichostatin A induced cell death in androgen receptor (AR)-positive cell lines to higher extent compared with AR-negative cell lines.

Androgen regulates apoptosis induced by TNFR family ligands via multiple signaling pathways in LNCaP.

It has been suggested in many studies that combined treatment with chemotherapeutic agents and apoptosis-inducing ligands belonging to TNFR family is a more effective strategy for cancer treatment. However, the role of androgen regulation of TNFR family-induced apoptosis in prostate cancer is poorly understood. In this study, we investigated the dose-dependent effects of androgen on TNF-alpha and TRAIL-mediated apoptosis in LNCaP.

Trichostatin A (TSA) sensitizes the human prostatic cancer cell line DU145 to death receptor ligands treatment.

The human prostatic carcinoma cell line DU145 has previously been found to be resistant to treatment with TNF-family ligands. However, TRAIL, TNF-alpha and anti-Fas antibodies (Ab) treatment in combination with the histone deacetylase inhibitor Trichostatin A (TSA) converted the phenotype of DU145 from resistant to sensitive. TSA induced 15% cell death but simultaneous treatment with TRAIL, TNF-alpha and anti-Fas Ab resulted in 55%, 70% and 40% cell death, respectively.

Tumor necrosis factor-related apoptosis-inducing ligand-mediated activation of mitochondria-associated nuclear factor-kappaB in prostatic carcinoma cell lines.

It has been suggested that some nuclear transcription factors may participate in the regulation of mitochondrial functions through transcriptional control of mitochondrial DNA. Very little is known about the response of transcription factors within mitochondria to the activation of death receptors. Recent publications indicate that nuclear factor-kappaB (NF-kappaB) is localized in mitochondria of mammalian cells.

Multiple effects of N-alpha-tosyl-L-phenylalanyl chloromethyl ketone (TPCK) on apoptotic pathways in human prostatic carcinoma cell lines.

TPCK is widely used as an inhibitor of chymotrypsin-like proteases but has recently been identified as an inhibitor of the PDK1/Akt pathway. In this study, we show that TPCK inhibits TRAIL-induced caspase activity but potentiates wortmannin-dependent caspase activity in prostatic carcinoma cell lines. The inhibitory activity of TPCK was found to be death ligand-specific since TPCK inhibits TRAIL-mediated caspase activity but does not affect Fas-induced caspase activity.

Death receptor-induced cell death in prostate cancer.

Prostate cancer mortality results from metastasis and is often coupled with progression from androgen-dependent to androgen-independent growth. Unfortunately, no effective treatment for metastatic prostate cancer increasing patient survival is available. The absence of effective therapies reflects in part a lack of knowledge about the molecular mechanisms involved in the development and progression of this disease.

Overexpression of BAD potentiates sensitivity to tumor necrosis factor-related apoptosis-inducing ligand treatment in the prostatic carcinoma cell line LNCaP.

Here we show that LNCaP, which is resistant to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis, becomes sensitive to TRAIL after overexpression of full-length, wild-type BAD (BAD WT). TRAIL induces caspase-dependent cleavage of BAD WT that results in generation of a M(r) 15,000 protein. LNCaP stably expressing truncated BAD (tBAD) and cells expressing mutated BAD at the caspase cleavage site were less sensitive to TRAIL treatment when compared to LNCaP expressing BAD WT.

TRAIL-DISC formation is androgen-dependent in the human prostatic carcinoma cell line LNCaP.

We and others have previously described that the androgen-responsive human prostatic carcinoma cell line LNCaP is resistant to TRAIL and that TRAIL-mediated apoptosis in LNCaP is PI3K/Akt-dependent. In this study, we found that LNCaP remained resistant to treatment with TRAIL after androgen deprivation even in the presence of the PI3K/Akt pathway inhibitor wortmannin. This resistance was determined by failure to form the TRAIL-DISC and by decreased TRAIL-R1 and TRAIL-R2 levels after androgen deprivation; the capacity of TRAIL to induce DISC formation was completely restored in the presence of DHT.

Bisindolylmaleimide IX facilitates tumor necrosis factor receptor family-mediated cell death and acts as an inhibitor of transcription.

Bisindolylmaleimides (Bis) were originally described as protein kinase C inhibitors. Several studies have shown that Bis potentiate tumor necrosis factor (TNF) receptor family-mediated apoptosis in lymphoid and dendritic cells, but the inhibition of protein kinase C cannot account for these effects (Zhou, T., Song, L.

Contribution of death receptor and mitochondrial pathways to Fas-mediated apoptosis in the prostatic carcinoma cell line PC3.

Background: Two main pathways of apoptosis in mammalian cells have been described: the death receptor pathway and the mitochondrial pathway. Two different cell types have been identified for Fas-mediated apoptosis, each using almost exclusively one of two different signaling pathways. Human prostatic carcinoma cell line, PC3 is sensitive to Fas-mediated apoptosis, but relation of receptor and mitochondrial pathways is not clear.