Fas-induced apoptosis of renal cell carcinoma is mediated by apoptosis signal-regulating kinase 1 via mitochondrial damage-dependent caspase-8 activation

Solute carrier family 35 member F2 is indispensable for papillary thyroid carcinoma progression through activation of transforming growth factor-β type I receptor/apoptosis signal-regulating kinase 1/mitogen-activated protein kinase signaling axis

Solute carrier family members control essential physiological functions and are tightly linked to human diseases. Solute carrier family 35 member F2 (SLC35F2) is aberrantly activated in several malignancies. However, the biological function and molecular mechanism of SLC35F2 in papillary thyroid carcinoma (PTC) are yet to be fully explored. Here, we showed that SLC35F2 was prominently upregulated in PTC tissues at both protein and mRNA expression level compared with matched adjacent normal tissues. Besides, the high expression of SLC35F2 was significantly associated with lymph node metastasis in patients with PTC. CRISPR/Cas9-mediated knockout of SLC35F2 attenuated the tumorigenic properties of PTC, including cell proliferation, migration and invasion and induced G1 phase arrest. In contrast, ectopic expression of SLC35F2 brought about aggressive malignant phenotypes of PTC cells. Moreover, SLC35F2 expedited the proliferation and migration of PTC cells by targeting transforming growth factor-β type I receptor (TGFBR1) and phosphorylation of apoptosis signal-regulating kinase 1 (p-ASK-1), thereby activating the mitogen-activated protein kinase signaling pathway. The malignant behaviors induced by overexpression of SLC35F2 could be abrogated by silencing of TGFBR1 using a specific inhibitor. We conducted the first study on SLC35F2 in thyroid cancer with the aim of elucidating the functional significance and molecular mechanism of SLC35F2. Our findings suggest that SLC35F2 exerts its oncogenic effect on PTC progression through the mitogen-activated protein kinase pathway, with dependence on activation of TGFBR-1 and apoptosis signal-regulating kinase 1.

Crosstalk between apoptosis and autophagy: molecular mechanisms and therapeutic strategies in cancer

Both apoptosis and autophagy are highly conserved processes that besides their role in the maintenance of the organismal and cellular homeostasis serve as a main target of tumor therapeutics. Although their important roles in the modulation of tumor therapeutic strategies have been widely reported, the molecular actions of both apoptosis and autophagy are counteracted by cancer protective mechanisms. While apoptosis is a tightly regulated process that is implicated in the removal of damaged or unwanted cells, autophagy is a cellular catabolic pathway that is involved in lysosomal degradation and recycling of proteins and organelles, and thereby is considered an important survival/protective mechanism for cancer cells in response to metabolic stress or chemotherapy. Although the relationship between autophagy and cell death is very complicated and has not been characterized in detail, the molecular mechanisms that control this relationship are considered to be a relevant target for the development of a therapeutic strategy for tumor treatment. In this review, we focus on the molecular mechanisms of apoptosis, autophagy, and those of the crosstalk between apoptosis and autophagy in order to provide insight into the molecular mechanisms that may be essential for the balance between cell survival and death as well as their role as targets for the development of novel therapeutic approaches.

Induction of apoptosis by luteolin involving akt inactivation in human 786-o renal cell carcinoma cells

There is a growing interest in the health-promoting effects of natural substances obtained from plants. Although luteolin has been identified as a potential therapeutic and preventive agent for cancer because of its potent cancer cell-killing activity, the molecular mechanisms have not been well elucidated. This study provides evidence of an alternative target for luteolin and sheds light on the mechanism of its physiological benefits. Treatment of 786-O renal cell carcinoma (RCC) cells (as well as A498 and ACHN) with luteolin caused cell apoptosis and death. This cytotoxicity was caused by the downregulation of Akt and resultant upregulation of apoptosis signal-regulating kinase-1 (Ask1), p38, and c-Jun N-terminal kinase (JNK) activities, probably via protein phosphatase 2A (PP2A) activation. In addition to being a concurrent substrate of caspases and event of cell death, heat shock protein-90 (HSP90) cleavage might also play a role in driving further cellular alterations and cell death, at least in part, involving an Akt-related mechanism. Due to the high expression of HSP90 and Akt-related molecules in RCC and other cancer cells, our findings suggest that PP2A activation might work in concert with HSP90 cleavage to inactivate Akt and lead to a vicious caspase-dependent apoptotic cycle in luteolin-treated 786-O cells.

Matrix metalloproteinase-1 contribution to sarcoma cell invasion

Matrix metalloproteinase-1 (MMP-1) activity has been linked to numerous disease processes from arthritis to ulcer. Its proteolytic activity has been implicated inconsistently in different steps of tumourigenesis and metastasis. The discrepancies may be attributable to our limited understanding of MMP-1 production, cellular trafficking, secretion and local activation. Specifically, regulation of MMP-1 directional delivery versus its general extracellular matrix secretion is largely unknown. Inhibition of prenylation by farnesyl transferase inhibitor (FTI-276) decreased extracellular MMP-1 and subsequently reduced invasiveness by 30%. Parallel, stable cell line RNAi knockdown of MMP-1 confirmed its role in cellular invasiveness. The prenylation agonist farnesyl pyrophosphate (FPP) partially normalized FTI-276 inhibited extracellular MMP-1 levels and invasion capacity while transiently delayed its cellular podia distribution. MMP-1 directional delivery to these structures were confirmed by combination of a MMP-1–specific fluorogenic substrate, a MMP1-Ds-Red fusion protein construct expression and DQ-collagen degradation, which demonstrated coupling of directional delivery and activation. MetaMorph analysis of cellular lamellipodia structures indicated that FTI-276 inhibited formation and delivery to these structures. Farnesyl pyrophosphate partially restored lamellipodia area but not MMP-1 delivery under the time frame investigated. These results indicate that MMP-1 directional delivery to podia structures is involved in the invasive activity of sarcoma cells, and this process is prenylation sensitive.

Hepatitis C virus-host interactions: Etiopathogenesis and therapeutic strategies

Hepatitis C virus (HCV) is a significant health problem facing the world. This virus infects more than 170 million people worldwide and is considered the major cause of both acute and chronic hepatitis. Persons become infected mainly through parenteral exposure to infected material by blood transfusions or injections with nonsterile needles. Although the sexual behavior is considered as a high risk factor for HCV infection, the transmission of HCV infection through sexual means, is less frequently. Currently, the available treatment for patients with chronic HCV infection is interferon based therapies alone or in combination with ribavirin and protease inhibitors. Although a sustained virological response of patients to the applied therapy, a great portion of patients did not show any response. HCV infection is mostly associated with progressive liver diseases including fibrosis, cirrhosis and hepatocellular carcinoma. Although the focus of many patients and clinicians is sometimes limited to that problem, the natural history of HCV infection (HCV) is also associated with the development of several extrahepatic manifestations including dermatologic, rheumatologic, neurologic, and nephrologic complications, diabetes, arterial hypertension, autoantibodies and cryglobulins. Despite the notion that HCV-mediated extrahepatic manifestations are credible, the mechanism of their modulation is not fully described in detail. Therefore, the understanding of the molecular mechanisms of HCV-induced alteration of intracellular signal transduction pathways, during the course of HCV infection, may offer novel therapeutic targets for HCV-associated both hepatic and extrahepatic manifestations. This review will elaborate the etiopathogenesis of HCV-host interactions and summarize the current knowledge of HCV-associated diseases and their possible therapeutic strategies.

Inhibition of IGF-1R-dependent PI3K activation sensitizes colon cancer cells specifically to DR5-mediated apoptosis but not to rhTRAIL

BACKGROUND

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) initiates apoptosis in tumor cells upon binding to its cognate agonistic receptors, death receptors 4 and 5 (DR4 and DR5). The activity of the insulin-like growth factor 1 (IGF-1) survival pathway is often increased in cancer, influencing both cell proliferation and apoptosis. We hypothesized that inhibiting the IGF-1 receptor (IGF-1R) using NVP-AEW541, a small molecular weight tyrosine kinase inhibitor of the IGF-1R, could increase death receptor (DR)-mediated apoptosis in colon cancer cells.

METHODS

The analyses were performed by caspase assay, flow cytometry, Western blotting, immunoprecipitation and fluorescent microscopy.

RESULTS

Preincubation with NVP-AEW541 surprisingly decreased apoptosis induced by recombinant human TRAIL (rhTRAIL) or an agonistic DR4 antibody while sensitivity to an agonistic DR5 antibody was increased. NVP-AEW541 could inhibit IGF-1-induced activation of the phosphatidylinositol 3-kinase (PI3K) pathway. The effects of the PI3K inhibitor LY294002 on TRAIL-induced apoptosis were similar to those of NVP-AEW541, further supporting a role for IGF-1R-mediated activation of PI3K. We show that PI3K inhibition enhances DR5-mediated caspase 8 processing but also lowers DR4 membrane expression and DR4-mediated caspase 8 processing. Inhibition of PI3K reduced rhTRAIL sensitivity independently of the cell line preference for either DR4- or DR5-mediated apoptosis signaling.

CONCLUSIONS

Our study indicates that individual effects on DR4 and DR5 apoptosis signaling should be taken into consideration when combining DR-ligands with PI3K inhibition.

Identification of candidate genes with pro-apoptotic properties by functional screening of randomly fragmented cDNA libraries

The sequences of many genomes are available; therefore, relevant methods are needed for rapid and efficient identification of functional genes. The ability of tumour cells to resist apoptosis induced by anticancer agents may decide the success of failure of tumour elimination. Although the CD95-signalling pathway is functional in tumour cells, the increased resistance of tumour cells to CD95-mediated apoptosis has been widely reported. In order to identify genes that might determine the response of tumour cells to CD95-mediated apoptosis, we modified the conventional technical knock out (TKO) strategy for isolation of genes that function in CD95-mediated apoptosis. Due to the fact that multiple different plasmids are usually introduced into the same cells, the effectiveness of the conventional TKO strategies is low. To overcome this obstacle, we replaced the conventional TKO strategy (based on stably expressed randomly fragmented cDNA libraries) with a multi-cycle selection procedure (based on transiently expressed randomly fragmented cDNA libraries with multi-cycle selection). Using this approach we could rapidly and significantly identify small numbers of antisense mRNA molecules, whose re-introduction into different tumour types confirmed their ability to block the pro-apoptotic function of their cognate genes. Thus, our modified TKO strategy provides a generally applicable procedure for the identification of functional genes with pro-apoptotic properties that may be clinically relevant to tumor therapy.