Role of Smac in determining the chemotherapeutic response of esophageal squamous cell carcinoma

POLE2 Regulates Apoptosis of Oral Squamous Cell Carcinoma Cells through the PI3K/AKT Signaling Pathway

OBJECTIVE

Oral squamous cell carcinoma (OSCC) is the most common malignant tumor of the head and neck, but its occurrence and progression mechanisms remain unclear. In addition-there is a lack of effective targeting drugs. The second major subunit of DNA polymerase (POLE2) catalyzes the prolongation of new strand replication and modifies exonuclease domain activity. Our previous study found that POLE2 was associated with OSCC progression, but the mechanism remains unclear.

METHODS

The expression of POLE2 in OSCC tissues was detected using immunological assays. Mann-Whitney U analysis was used to investigate the relationship between POLE2 gene expression and tumor classification and prognosis of OSCC. POLE2 expression was inhibited in OSCC cells, and the effects of gene and protein expression were detected using RT-PCR and Western blotting. The POLE2 knockout model was constructed by transfecting a lentiviral vector. Cell proliferation, apoptosis, and migration were detected using various assays including colony formation, MTT, flow cytometry, wound healing assay, Transwell assay, and the Human Apoptosis Antibody Array. The animal model of OSCC was established by subcutaneous injection of transfected HN6 into 4-week-old female nude mice. After 30 days, tumors were removed under anesthesia and tumor weight and dimension were recorded. Tumor cell proliferation was analyzed using Ki67 staining.

RESULTS

POLE2 gene levels were significantly higher in the OSCC tissues than in the normal tissues. In addition, POLE2 gene levels were statistically correlated with tumor classification and prognosis. Silencing POLE2 inhibited the proliferation of oral cancer cells and promoted apoptosis in vitro. Animal experiments also supported a positive correlation between POLE2 and OSCC tumor formation. We further demonstrated that POLE2 could upregulate the expression of apoptosis-related proteins such as caspase-3, CD40, CD40L, DR6, Fas, IGFBP-6, p21, and SMAC. In addition, POLE2 regulated OSCC development by inhibiting the PI3K/AKT signaling pathway.

CONCLUSION

POLE2 is closely related to the progression of OSCC. Thus, POLE2 may be a potential target for OSCC treatment.

Silencing POLE2 promotes apoptosis and inhibits proliferation of oral squamous cell carcinomas by inhibiting PI3K/AKT signaling pathway

Oral squamous cell carcinoma is the most common malignant tumor in the head and neck at present, but the mechanism of its occurrence and development is still unclear, and there is still a lack of effective targeting drugs. The second major subunit of DNA polymerase (POLE2) has exonuclease activity and can catalyze the replication and modification of new chains. Our previous studies have found that it is associated with OSCC progression, but the mechanism is unclear.The expression of POLE2 in OSCC was detected by immunological method. The expression of POLE2 was inhibited in OSCC cells, and the biological function of the cells was detected by RT-PCR and Western Blot. Cell proliferation, apoptosis and migration were detected by colony formation, MTT, flow cytometry, wound healing and Transwell. The expression level of POLE2 gene in OSCC was significantly higher than that in normal tissues. In addition, the expression level of POLE2 gene was significantly different from the tumor type and prognosis. During the development of oral squamous cell carcinoma, silencing POLE2 inhibits the proliferation of oral cancer cells and promotes apoptosis. The results of animal experiments also support the positive correlation between POLE2 and OSCC progression. We further demonstrated that POLE2 can up-regulate the downregulation of apoptosis-related proteins such as Caspase3, CD40, CD40L, DR6, Fas, IGFBP-6, P21, and SMAC. In addition, POLE2 regulates OSCC progression by inhibiting the PI3K/AKT pathway. POLE2 is closely related to the progression of OSCC, and POLE2 may be a potential target for OSCC treatment.

The GSTP1/MAPKs/BIM/SMAC modulatory actions of nitazoxanide: Bioinformatics and experimental evidence in subcutaneous solid Ehrlich carcinoma-inoculated mice

AIMS

Ehrlich ascites carcinoma and its subcutaneous inoculated solid tumour form (SEC) are reliable models for chemotherapeutic molecular targets exploration. Novel chemotherapeutic approaches are identified as molecular targets for intrinsic apoptosis, like the modulation of the second mitochondria-derived activator of caspases (SMAC). SMAC is a physiological substrate of mitogen-activated protein kinases (MAPKs). Glutathione-S-transferase P1 (GSTP1) and its close association with MAPKs play an important role in malignant cell proliferation, metastasis, and resistance to chemotherapeutics. Nitazoxanide (NTZ) is an emerging cancer therapy and its targeted GSTP1 evidence remains a knowledge need.

MAIN METHODS

In the present mice-established SEC, the chemotherapeutic roles of oral NTZ (200 mg/kg/day) and 5-fluorouracil (5-FU; 20 mg/kg/day, intraperitoneally) regimens were evaluated by measuring changes in tumour mass, the tumour MAPKs, cytochrome c, Bcl-2 interacting mediator of cell death (BIM), and SMAC signalling pathway in addition to its molecular downstream; caspases 3 and 9.

KEY FINDINGS

Computational analysis for these target protein interactions showed direct-ordered interactions. After individual therapy with NTZ and 5-FU regimens, the histological architecture of the extracted tumour discs revealed decreases in viable tumour regions with significant necrosis surrounds. These findings were consistent with gross tumour sizes. Each separate regimen lowered the remarkable GSTP1 and elevated the low MAPKs expressions, cytochrome c, BIM, SMAC, and caspases 3, and 9 in EST tissues.

SIGNIFICANCE

The chemotherapeutic activity of NTZ in SEC was proven. Additionally, NTZ possesses a SMAC modulatory activity that, following thorough research, should be taken into consideration as a chemotherapeutic approach in solid tumours.

SMAC exhibits anti-tumor effects in ECA109 cells by regulating expression of inhibitor of apoptosis protein family

BACKGROUND

The poor prognosis and rising incidence of esophageal cancer highlight the need for improved therapeutics that are essential prior to treatment. LCL161 is an SMAC (second mitochondrial activator of caspases) mimic and inhibitor of apoptosis protein (IAP) antagonist which exhibits anti-tumor effects and improves the chemical sensitivity of many cancers.

AIM

To ascertain the effects and mechanisms of the SMAC analog LCL161 on esophageal cancer cells.

METHODS

MTT assay and TUNEL assay were used to detect cell proliferation and apoptosis, respectively. Western blot analysis was used to study the molecular mechanisms of LCL161-induced death of ECA109 cells.

RESULTS

LCL161 decreased ECA109 cell proliferation in dose- and time-dependent manner and induced apoptosis of ECA109 cells in a dose-dependent manner. Also, LCL161 induced a significant decrease in the expression of the XIAP and significant increase in the expression of Caspase-3. In addition, Bax increased significantly with increasing concentrations of LCL161, and the relative expression of Bax was significantly different between groups.

CONCLUSION

These findings support the hypothesis that LCL161 can inhibit proliferation and induce apoptosis in esophageal cancer cells by regulating the expression of IAP family members, suggesting that it has potential to be an effective treatment for esophageal squamous cell carcinoma.

Screening and identification of key biomarkers in alimentary tract cancers: A bioinformatic analysis

BACKGROUND

Alimentary tract cancers (ATCs) are the most malignant cancers in the world. Numerous studies have revealed the tumorigenesis, diagnosis and treatment of ATCs, but many mechanisms remain to be explored.

METHODS

To identify the key genes of ATCs, microarray datasets of oesophageal cancer, gastric cancer and colorectal cancer were obtained from the Gene Expression Omnibus (GEO) database. In total, 207 differentially expressed genes (DEGs) were screened. KEGG and GO function enrichment analyses were conducted, and a protein-protein interaction (PPI) network was generated and gene modules analysis was performed using STRING and Cytoscape.

RESULTS

Five hub genes were screened, and the associated biological processes indicated that these genes were mainly enriched in cellular processes, protein binding and metabolic processes. Clinical survival analysis showed that COL10A1 and KIF14 may be significantly associated with the tumorigenesis or pathology grade of ATCs. In addition, relative human ATC cell lines along with blood samples and tumour tissues of ATC patients were obtained. The data proved that high expression of COL10A1 and KIF14 was associated with tumorigenesis and could be detected in blood.

CONCLUSION

In conclusion, the identification of hub genes in the present study helped us to elucidate the molecular mechanisms of tumorigenesis and identify potential diagnostic indicators and targeted treatment for ATCs.

Long non-coding RNAs MACC1-AS1 and FOXD2-AS1 mediate NSD2-induced cisplatin resistance in esophageal squamous cell carcinoma

The nuclear receptor-binding SET domain (NSD) protein family encoding histone lysine methyltransferases is involved in cancer progression. However, the role of NSDs in esophageal squamous cell carcinoma (ESCC) remains unclear. Here we examined the expression of NSDs in cisplatin-resistant and parental ESCC cells and revealed the upregulation of NSD2 in cisplatin-resistant cells. Ectopic expression of NSD2 increased cisplatin resistance and attenuated cisplatin-induced apoptosis. Colony formation assay indicated that NSD2 overexpression enhanced long-term survival of ESCC cells after treatment with cisplatin. In contrast, knockdown of NSD2 inhibited ESCC cell proliferation and sensitized ESCC cells to cisplatin. Depletion of NSD2 augmented the cytotoxic effect of cisplatin on EC109 xenograft tumors. NSD2 stimulated long non-coding RNA MACC1-AS1 in ESCC cells. Knockdown of MACC1-AS1 impaired NSD2-induced cisplatin resistance. Moreover, MACC1-AS1 overexpression promoted ESCC cell proliferation and cisplatin resistance. Clinically, MACC1-AS1 was upregulated in ESCC relative to adjacent noncancerous tissues. High MACC1-AS1 levels were significantly associated with reduced overall survival of ESCC patients. There was a positive correlation between MACC1-AS1 and NSD2 expression in ESCC specimens. Taken together, MACC1-AS1 induced by NSD2 mediates resistance to cisplatin in ESCC and may represent a novel target to improve cisplatin-based chemotherapy.

Role of Smac, survivin, XIAP, and Omi/HtrA2 proteins in determining the chemotherapeutic response of patients with cervical cancer treated with neoadjuvant chemotherapy

Neoadjuvant chemotherapy (NACT) followed by radical surgical hysterectomy and pelvic lymph node dissection is considered an effective method to treat patients with bulky stage IB-IIA cervical cancer, but not all patients benefit from NACT. Apoptotic proteins play important roles in the progression of chemotherapy, and second mitochondria-derived activator of caspase (Smac) may have a cooperative relationship with Omi/HtrA2, leading to carcinogenesis and chemotherapy resistance. Chemosensitivity is an important prognostic factor for cervical cancer patients. The aim of this study was to evaluate the significance of Smac, survivin, X-linked inhibitor-of-apoptosis protein (XIAP), and Omi/HtrA2 expression in predicting the response to neoadjuvant chemotherapy and the prognostic significance of te expression of these proteins in cervical cancer patients. Our findings showed that low expression levels of survivin and high expression levels of Omi/HtrA2 in chemotherapy-responsive cervical carcinoma patients significantly increased chemosensitivity.

RYBP inhibits esophageal squamous cell carcinoma proliferation through downregulating CDC6 and CDC45 in G1-S phase transition process

AIMS

RING1 and YY1-binding protein (RYBP) is an epigenetic regulator and plays crucial roles in embryonic development. The anti-tumor effect of RYBP has been reported in several cancers recently, but the role of RYBP in esophageal squamous cell carcinoma (ESCC) has not been fully elucidated. The present study aimed to investigate the biological function and the underlying molecular mechanisms of RYBP in ESCC.

MATERIALS AND METHODS

We detected the expression of RYBP in ESCC tissue microarrays (TMA) by immunohistochemistry. Cell proliferation was assessed by CCK8 and colony formation assays. Cell cycle was analyzed by flow cytometry. Gene expression was determined by transcriptome arrays, quantitative real-time PCR (qRT-PCR) and Western blot. Four-week-old male nude mice were used to evaluate the effect of RYBP in ESCC growth.

KEY FINDINGS

We found that RYBP was downregulated in ESCC compared with adjacent normal tissues. A high level of RYBP expression predicted a better outcome of ESCC patients. Furthermore, overexpression of RYBP inhibited ESCC growth both in vitro and in vivo. Transcriptome arrays and functional studies showed that RYBP decreased the expression of genes related to cell cycles, especially CDC6 and CDC45, which were essential to initiate the DNA replication and G1-S transition.

SIGNIFICANCE

Taken together, our study suggests that RYBP suppresses ESCC proliferation by downregulating CDC6 and CDC45, thus inhibiting the G1-S transition.

Metformin induces human esophageal carcinoma cell pyroptosis by targeting the miR-497/PELP1 axis

Evasion of apoptosis is a major contributing factor to the development of chemo- and radiotherapy resistance. Therefore, activation of non-apoptotic programmed cell death (PCD) could be an effective alternative against apoptosis-resistant cancers. In this study, we demonstrated in vitro and in vivo that metformin can induce pyroptosis, a non-apoptotic PCD, in esophageal squamous cell carcinoma (ESCC), a commonly known chemo-refractory cancer, especially at its advanced stages. Proline-, glutamic acid- and leucine-rich protein-1 (PELP1) is a scaffolding oncogene and upregulated PELP1 in advanced stages of ESCC is highly associated with cancer progression and patient outcomes. Intriguingly, metformin treatment leads to gasdermin D (GSDMD)-mediated pyroptosis, which is abrogated by forced expression of PELP1. Mechanistically, metformin induces pyroptosis of ESCC by targeting miR-497/PELP1 axis. Our findings suggest that metformin and any other pyroptosis-inducing reagents could serve as alternative treatments for chemo- and radiotherapy refractory ESCC or other cancers sharing the same pyroptosis mechanisms.

Gemcitabine combined with an engineered oncolytic vaccinia virus exhibits a synergistic suppressive effect on the tumor growth of pancreatic cancer

Pancreatic cancer (PC) is a lethal solid malignancy with resistance to traditional chemotherapy. Recently, considerable studies have demonstrated the ubiquitous antitumor properties of gene therapy mediated by the oncolytic vaccinia virus. The second mitochondrial-derived activator of caspase (Smac) has been identified as an innovative tumor suppressor that augments the chemosensitivity of cancer cells. However, the therapeutic value of oncolytic vaccinia virus (oVV)-mediated Smac gene transfer in pancreatic cancer is yet to be elucidated. In the present study, oncolytic vaccinia virus expressing Smac (second mitochondrial-derived activator of caspase) (oVV-Smac) was used to examine its beneficial value when used alone or with gemcitabine in pancreatic cancer in vitro and in vivo. The expression of Smac was evaluated by western blot analysis and quantitative polymerase chain reaction, oVV-Smac cytotoxicity by MTT assay, and apoptosis by flow cytometry and western blot analysis. Furthermore, the inhibitory effect of oVV-Smac combined with gemcitabine was also evaluated. The results indicated that oVV-Smac achieved high levels of Smac, greater cytotoxicity, and potentiated apoptosis. Moreover, co-treatment with oVV-Smac and gemcitabine resulted in a synergistic effect in vitro and in vivo. Therefore, our findings advance oVV-Smac as a potential therapeutic candidate in pancreatic cancer and indicated the synergistic effects of co-treatment with oVV-Smac and gemcitabine.

Predictive biomarkers for response of esophageal cancer to chemo(radio)therapy: A systematic review and meta-analysis

BACKGROUND

Esophageal cancer remains a major public health issue worldwide. In clinical practice, chemo(radio)therapy is an important approach to patients with esophageal cancer. Only the part of patients who respond to chemo(radio)therapy achieve better long-term outcome. In this case, predictive biomarkers for response of esophageal cancer patients treated with chemo(radio)therapy are of importance. Meta-analysis of P53 for predicting esophageal cancer response has been reported before and is not included in our study. We performed a systematic review and meta-analysis to summarize and evaluate the biomarkers for predicting response to chemo(radio)therapy.

METHOD

PubMed, Web of Science and the Ovid databases were searched to identify eligible studies published in English before March 2017. The risk ratio (or relative risk, RR) was retrieved in articles regarding biomarkers for predicting response of esophageal cancer patients treated with neoadjuvant therapy or chemo(radio)therapy. Fixed and random effects models were used to undertake the meta-analysis as appropriate.

RESULT

Forty-six articles reporting 56 biomarkers correlated with the response were finally included. Meta-analyses were carried out when there was more than one study related to the reported biomarker. Results indicated that low expression of (or IHC-negative) COX2, miR-200c, ERCC1 and TS was individually associated with prediction of response. The RR was 1.64 (n = 202, 95% CI 1.22-2.19, P < 0.001), 1.96 (n = 162, 95% CI 1.36-2.83, P < 0.001), 2.55 (n = 206, 95% CI 1.80-3.62, P < 0.001) and 1.69 (n = 144, 95% CI 1.10-2.61, P = 0.02), respectively. High expression of (or IHC-positive) CDC25B and p16 was individually related to prediction of response. The RR was 0.62 (n = 159, 95% CI 0.43-0.89, P = 0.01) and 0.62 (n = 142, 95% CI 0.43-0.91, P = 0.01), respectively.

CONCLUSION

Low expression of (or IHC-negative) COX2, miR-200c, ERCC1 and TS, or high expression of (or IHC-positive) CDC25B and p16 are potential biomarkers for predicting the response of esophageal cancer patients treated with chemo(radio)therapy.

Overexpression of stathmin plays a pivotal role in the metastasis of esophageal squamous cell carcinoma

Purpose

Esophageal squamous cell carcinoma (ESCC) is a serious malignant tumor that affects human health. We analyzed the correlation between serum stathmin level and ESCC and elucidated the molecular mechanisms of stathmin's promotion of ESCC cell invasion and metastasis.

Methods

Stathmin level in ESCC and healthy control serum were detected by enzyme-linked immunosorbent assay (ELISA), and the clinical parameters were analyzed. We established ESCC cells with stathmin overexpression or knockdown and then evaluated the effects of stathmin on invasion and metastasis in ESCC. Differentially expressed genes were analyzed by Human Transcriptome Array and confirmed by RT-PCR. The expression levels of the integrin family, focal adhesion kinase (FAK) and extracellular signal-regulated kinase (ERK) were detected by immunoblotting.

Results

Serum levels of stathmin were significantly higher in ESCC than in control serum and associated with lymph node metastasis, tumor stage and size. Furthermore, we found that stathmin promoted migration and invasion of ESCC cells in vitro and in vivo. In addition, we confirmed that the activation of the integrinα5β1/FAK/ERK pathway is increased in stathmin-overexpression cells and accelerates cell motility by enhancing cell adhesion ability.

Conclusion

Stathmin may predict a potential metastasis biomarker for ESCC.

Protein and gene expression characteristics of heterogeneous nuclear ribonucleoprotein H1 in esophageal squamous cell carcinoma

AIM

To investigate the expression characteristics of heterogeneous nuclear ribonucleoprotein H1 (HNRNPH1) mRNA and protein in cell lines and tissues of esophageal squamous cell carcinoma (ESCC).

METHODS

Western blotting was used to assess the expression of HNRNPH1 protein in seven ESCC cell lines and 30 paired fresh tissue specimens. The subcellular localization of HNRNPH1 was determined by immunofluorescence in ESCC cells. The RNA sequencing data from 87 patients with ESCC were obtained from the cancer genome atlas (TCGA), and the expression and clinical characteristics analysis of different transcript variants of HNRNPH1 were evaluated in this dataset. In addition, immunohistochemistry was carried out to detect the expression of HNRNPH1 protein in 125 patients.

RESULTS

The expression of HNRNPH1 protein varied across different ESCC cell lines. It was exclusively restricted to the nucleus of the ESCC cells. There are two transcript variants of the HNRNPH1 gene. Variant 1 was constitutively expressed, and its expression did not change during tumorigenesis. In contrast, levels of variant 2 were low in non-tumorous tissues and were dramatically increased in ESCC (P = 0.0026). The high levels of variant 2 were associated with poorer differentiated tumors (P = 0.0287). Furthermore, in paired fresh tissue specimens, HNRNPH1 protein was overexpressed in 73.3% (22/30) of neoplastic tissues. HNRNPH1 was significantly upregulated in ESCC, with strong staining in 43.2% (54/125) of tumor tissues and 22.4% (28/125) of matched non-cancerous tissues (P = 0.0005). Positive HNRNPH1 expression was significantly associated with poor tumor differentiation degree (P = 0.0337).

CONCLUSION

The different alternative transcript variants of HNRNPH1 exhibited different expression changes during tumorigenesis. Its mRNA and protein were overexpressed in ESCC and associated with poorer differentiation of tumor cells. These findings highlight the potential of HNRNPH1 in the therapy and diagnosis of ESCC.

NDRG1 overexpression promotes the progression of esophageal squamous cell carcinoma through modulating Wnt signaling pathway

N-myc down-regulated gene 1 (NDRG1) has been shown to regulate tumor growth and metastasis in various malignant tumors and also to be dysregulated in esophageal squamous cell carcinoma (ESCC). Here, we show that NDRG1 overexpression (91.9%, 79/86) in ESCC tumor tissues is associated with poor overall survival of esophageal cancer patients. When placed in stable transfectants of the KYSE 30 ESCC cell line generated by lentiviral transduction with the ectopic overexpression of NDRG1, the expression of transducin-like enhancer of Split 2 (TLE2) was decreased sharply, however β−catenin was increased. Mechanistically, NDRG1 physically associates with TLE2 and β−catenin to affect the Wnt pathway. RNA interference and TLE2 overexpression studies demonstrate that NDRG1 fails to active Wnt pathway compared with isogenic wild-type controls. Strikingly, NDRG1 overexpression induces the epithelial mesenchymal transition (EMT) through activating the Wnt signaling pathway in ESCC cells, decreased the expression of E-cadherin and enhanced the expression of Snail. Our study elucidates a mechanism of NDRG1-regulated Wnt pathway activation and EMT via affecting TLE2 and  β-catenin expression in esophageal cancer cells. This indicates a pro-oncogenic role for NDRG1 in esophageal cancer cells whereby it modulates tumor progression.

YM155, a survivin suppressant, triggers PARP-dependent cell death (parthanatos) and inhibits esophageal squamous-cell carcinoma xenografts in mice

Here we demonstrated that sepantronium bromide (YM155), a survivin suppressant, inhibited esophageal squamous-cell carcinoma (ESCC) growth in mice bearing human ESCC xenografts without affecting body weight. In cell culture, YM155 decreased survivin levels and caused PARP-1 activation, poly-ADP polymer formation, and AIF translocation from the cytosol to the nucleus. Genetic knockdown of PARP-1 or AIF abrogated YM155-induced parthanatos cell death. Furthermore, FOS, JUN and c-MYC gene transcription, which is stimulated by activated PARP-1, was increased following YM155 treatment. Our data demonstrate that YM155 did not trigger apoptosis, but induced parthanatos, a cell death dependent on PARP-1 hyper-activation, and support clinical development of YM155 in ESCC.

Apollon modulates chemosensitivity in human esophageal squamous cell carcinoma

Patients with esophageal squamous cell carcinoma (ESCC) are often diagnosed with advanced diseases that respond poorly to chemotherapy. Here we reported that Apollon, a membrane-associated inhibitor of apoptosis protein, was overexpressed in ESCC cell lines and clinical ESCC tissues, and Apollon overexpression clinically correlated with poor response to chemotherapy (P = 0.001), and short overall survival (P = 0.021). Apollon knockdown increased cisplatin/docetaxel-induced apoptosis, mitochondrial dysfunction and cytochrome c release in two ESCC cell lines. Apollon knockdown potentiated cisplatin/docetaxel-induced long-term cell growth inhibition, and enhanced chemosensitivity of ESCC cells to cisplatin/docetaxel in xenograft tumor models. Apollon knockdown also enhanced cisplatin/docetaxel-induced activation of caspase-8 (extrinsic pathway) and caspase-9 (intrinsic pathway) in ESCC cells and xenograft tumor models. Mechanism studies revealed that the effect of Apollon on chemosensitivity is mainly mediated by Smac. Apollon expression strongly and negatively correlated with Smac expression in clinical ESCC tissues (P = 0.001). Apollon targeted Smac for degradation in ESCC cells. The effect of Apollon on chemosensitivity was reversed by Smac knockdown in ESCC cells. Taken together, our data show association of Apollon expression with chemotherapeutic response in ESCC, and provide a strong rationale for combining Apollon antagonism with chemotherapy to treat ESCC.

Indomethacin induces apoptosis in the EC109 esophageal cancer cell line by releasing second mitochondria-derived activator of caspase and activating caspase-3

The use of non‑steroidal anti‑inflammatory drugs (NSAIDs) has been associated with a reduced risk of various types of cancer, including esophageal cancer. However, the mechanisms underlying the antineoplastic effects of NSAIDs in esophageal cancer remain to be elucidated. In the present study, a significant inhibition in cell viability was observed in the EC109 cells following treatment with different concentrations of indomethacin, and these effects occurred in a dose‑ and time‑dependent manner. This inhibition was due to the release of second mitochondria‑derived activator of caspase (Smac) into the cytosol and the activation of caspase‑3. Subsequently, flow cytometry was performed to investigate indomethacin‑induced apoptosis following the overexpression or knockdown of Smac, and western blot analysis was performed to determine the expression of Smac and the activation of caspase‑3. Overexpression of Smac was promoted apoptosis, while downregulation of Smac significantly inhibited apoptosis. Western blot analysis demonstrated that indomethacin induced apoptosis through releasing Smac into the cytosol and activating caspase‑3. These results indicated that Smac is essential for the apoptosis induced by indomethacin in esophageal cancer cells.

Differential response of head and neck cancer cell lines to TRAIL or Smac mimetics is associated with the cellular levels and activity of caspase-8 and caspase-10

Background:

Current treatment strategies for head and neck cancer are associated with significant morbidity and up to 50% of patients relapse, highlighting the need for more specific and effective therapeutics. Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) and Smac mimetics (SMs) are promising anticancer agents, but their effect on head and neck squamous cell carcinoma (HNSCC) remains unknown.

Methods:

We examined the response of a panel of nine HNSCC cell lines to TRAIL and SMs and investigated the mechanism of cell type-specific response by functional analysis.

Results:

Head and neck cancer cell lines revealed a converse response pattern with three cell lines being highly sensitive to Smac-164 (SM) but resistant to TRAIL, whereas the other six were sensitive to TRAIL but resistant to SM. Distinct protein expression and activation patterns were found to be associated with susceptibility of HNSCC cell lines to TRAIL and SM. Tumour necrosis factor-related apoptosis-inducing ligand sensitivity was associated with high caspase-8 and Bid protein levels, and TRAIL-sensitive cell lines were killed via the type II extrinsic apoptotic pathway. Smac mimetic-sensitive cells expressed low levels of caspase-8 and Bid but had high TNF-α expression. Smac mimetic-induced cell death was associated with caspase-10 activation, suggesting that in the absence of caspase-8, caspase-10 mediates response to SM. Cotreatment with TNF-α sensitised the resistant cells to SM, demonstrating a decisive role for TNF-α-driven feedback loop in SM sensitivity.

Conclusions:

Tumour necrosis factor-related apoptosis-inducing ligand and SMs effectively kill HNSCC cell lines and therefore represent potential targeted therapeutics for head and neck cancer. Distinct molecular mechanisms determine the sensitivity to each agent, with levels of TNF-α, caspase-8, Bid and caspase-10 providing important predictive biomarkers of response to these agents.

Receptor interactive protein kinase 3 promotes Cisplatin-triggered necrosis in apoptosis-resistant esophageal squamous cell carcinoma cells

Cisplatin-based chemotherapy is currently the standard treatment for locally advanced esophageal cancer. Cisplatin has been shown to induce both apoptosis and necrosis in cancer cells, but the mechanism by which programmed necrosis is induced remains unknown. In this study, we provide evidence that cisplatin induces necrotic cell death in apoptosis-resistant esophageal cancer cells. This cell death is dependent on RIPK3 and on necrosome formation via autocrine production of TNFα. More importantly, we demonstrate that RIPK3 is necessary for cisplatin-induced killing of esophageal cancer cells because inhibition of RIPK1 activity by necrostatin or knockdown of RIPK3 significantly attenuates necrosis and leads to cisplatin resistance. Moreover, microarray analysis confirmed an anti-apoptotic molecular expression pattern in esophageal cancer cells in response to cisplatin. Taken together, our data indicate that RIPK3 and autocrine production of TNFα contribute to cisplatin sensitivity by initiating necrosis when the apoptotic pathway is suppressed or absent in esophageal cancer cells. These data provide new insight into the molecular mechanisms underlying cisplatin-induced necrosis and suggest that RIPK3 is a potential marker for predicting cisplatin sensitivity in apoptosis-resistant and advanced esophageal cancer.

SMAC-armed vaccinia virus induces both apoptosis and necroptosis and synergizes the efficiency of vinblastine in HCC

Hepatocellular carcinoma (HCC) has particularly high incidence rate in Asia and its resistance to the chemotherapeutic drugs and cell death make it intractable. Vaccinia virus (VV) is a potential vehicle and has been widely used in cancer therapy. SMAC/DIABLO is a critical factor in activating caspases and eliminating inhibition of IAPs when the programmed cell death is promoted. In this study, we constructed a tumor-targeted vaccinia virus carrying SMAC/DIABLO gene that was knocked in the region of viral thymidine kinase gene (VV-SMAC). Our results showed that VV-SMAC efficiently infected and destroyed HCC cells via triggering both caspase-dependent apoptosis and necroptosis with depletion of IAPs. Furthermore, ripoptosome, a prerequisite complex of necroptosis, was assembled and induced by VV-SMAC. In addition, the combination of VV-SMAC and vinblastine represented a synergistic effect on HCC cells. In summary, our data suggest that VV-SMAC is a potential candidate and combination of VV-SMAC and vinblastine may provide a new avenue in treatment of HCC.

Clinical significance of Smac and survivin expression in breast cancer patients treated with anthracycline‑based neoadjuvant chemotherapy

The second mitochondria‑derived activator of caspases (Smac), an antagonist of the inhibitor of apoptosis protein (IAP), increases chemosensitivity in vitro. Survivin, an IAP family member, mediates cancer cell survival and chemoresistance. The present study investigated the correlation between Smac and survivin expression in primary breast cancer, and the sensitivity to anthracycline during neoadjuvant chemotherapy (NAC). Pre‑treatment biopsies and post‑anthracycline treatment tumor sections were analyzed from 98 cases. Biomarker expression was evaluated by immunohistochemistry in tumor samples from clinical stage II and III anthracycline‑based NAC‑treated breast cancer. A univariate analysis indicated that the estrogen receptor (ER), Smac and survivin were significantly predictive of a pathological complete response (pCR) (P=0.004, 0.001 and 0.037, respectively) in pre‑chemotherapy samples. ER, Smac and survivin expression was also significant for pCR on the multivariate analysis (P=0.001, 0.031 and 0.012, respectively). An inverse association was identified between survivin and Smac expression (r=‑0.217, P=0.032; and r=‑0.335, P=0.003, respectively) prior to and following NAC. The patients with low survivin expression or high Smac expression had significantly longer disease‑free survival (DFS; P=0.012 and P=0.020, respectively) and overall survival (OS; P=0.01 and P=0.033, respectively) compared with the patients with high survivin or low Smac expression. Cox regression analyses demonstrated that survivin, Smac and clinical stage were independent predictors for DFS and OS. The present study indicated the significance of Smac and survivin in determining the breast cancer response to anthracycline‑based chemotherapy, and may permit further stratifying of pre‑chemotherapy patients to undertake more tailored treatments.

IAP proteins as targets for drug development in oncology

The inhibitors of apoptosis (IAPs) constitute a family of proteins involved in the regulation of various cellular processes, including cell death, immune and inflammatory responses, cell proliferation, cell differentiation, and cell motility. There is accumulating evidence supporting IAP-targeting in tumors: IAPs regulate various cellular processes that contribute to tumor development, such as cell death, cell proliferation, and cell migration; their expression is increased in a number of human tumor samples, and IAP overexpression has been correlated with tumor growth, and poor prognosis or low response to treatment; and IAP expression can be rapidly induced in response to chemotherapy or radiotherapy because of the presence of an internal ribosome entry site (IRES)-dependent mechanism of translation initiation, which could contribute to resistance to antitumor therapy. The development of IAP antagonists is an important challenge and was subject to intense research over the past decade. Six molecules are currently in clinical trials. This review focuses on the role of IAPs in tumors and the development of IAP-targeting molecules for anticancer therapy.

Metallopanstimulin-1 regulates invasion and migration of gastric cancer cells partially through integrin β4

MPS-1 (metallopanstimulin-1), also known as ribosomal protein S27, was overexpressed in gastric cancer cells. However, how MPS-1 contributes to gastric carcinogenesis has not been well characterized. Here, we show that high expression of MPS-1 was observed in gastric cancer tissues and associated with gastric cancer cell metastasis. Alteration of MPS-1 expression regulates invasion and migration of gastric cancer cells both in vitro and in vivo. Furthermore, by using Signal-Net and cluster analyses of microarray data we identified integrin β4 (ITGB4) as a downstream target of MPS-1 that mediates its effects on cell metastasis. Knockdown of MPS-1 expression in gastric cancer cells led to significant reduction of ITGB4 expression at both the RNA and protein levels. Mechanically, we found that overexpression of ITGB4 in MPS-1 knockdown cells largely recovers the ability of invasion and migration. Conversely, knockdown of ITGB4 partially reduced cell invading/migrating ability induced by MPS-1 overexpression. Moreover, MPS-1 and ITGB4 expressions are positively correlated in gastric cancer cell lines and tissues. Finally, the survival analyses show that the expression of MPS-1 and ITGB4 is associated with poor outcomes in gastric cancer patients. Collectively, our findings suggest that MPS-1 regulates cell invasiveness and migration partially through ITGB4 and that MPS-1/ITGB4 signaling axis may serve as therapeutic targets in the treatment of gastric cancer.

Overexpression of Smac promotes Cisplatin-induced apoptosis by activating caspase-3 and caspase-9 in lung cancer A549 cells

Second mitochondrial-derived activator of caspase (Smac) plays crucial roles in mitochondrial apoptosis pathways and promotes chemotherapy-induced apoptosis. In this study, Smac levels were examined in various lung cancer cell lines, and the effects of overexpressed Smac in the nonsmall-cell lung cancer cell line A549 were assayed by stable transfection of Smac. Subsequently, MTT assays, cell counting, and flow cytometry were applied to show that overexpression of Smac inhibits cell viability and cell growth and enhances apoptosis after cisplatin treatment. Western blotting was performed before and after cisplatin treatment to demonstrate that drug treatment could release Smac from mitochondria into the cytosol and promote apoptosis by activating caspase-3 and caspase-9. Promotion of apoptosis by cytosolic Smac could be blocked by pretreating cells with the caspase-9 inhibitor z-LEHD-FMK. Our findings indicate that overexpressed Smac significantly inhibited A549 cell growth and promoted apoptosis following cisplatin treatment due to the release of Smac from mitochondria into the cytosol, which increased the activities of caspase-3 and caspase-9.

Progress in understanding the role of inhibitor of apoptosis proteins in molecular targeted therapy of esophageal cancer

The apoptosis and antiapoptotic signaling pathways play a critical role in the embryonic and lymphocyte development, immune system modulation, and tissue homeostasis, as well as carcinogenesis. As inhibitor of apoptosis proteins (IAPs) are highly expressed in several neoplasms and are closely related to carcinogenesis, cancer progression, radiochemotherapeutic resistance, and prognosis, therapies targeting IAPs have become a research hotspot for molecular targeted therapy of tumors. In recent years, many agents targeting IAPs which are being evaluated in clinical trials are showing promising prospect for neoplastic therapy. As such, the identification of key roles of IAPs in esophageal cancer has revealed their potential value as therapeutic targets. This report reviews the progress in understanding the role of IAPs in molecular targeted therapy of esophageal cancer.

An apoptosis-independent role of SMAC in tumor suppression

Reduced expression of the pro-apoptotic protein SMAC (second mitochondria-derived activator of caspase) has been reported to correlate with cancer progression, while its significance and underlying mechanisms are poorly understood. In this study, we investigated the role of SMAC in intestinal tumorigenesis using both human samples and animal models. Decreased SMAC expression was found to correlate with increased cIAP2 expression and higher grades of human colon cancer. In mice, SMAC deficiency significantly increased the incidence and size of colon tumors induced by azoxymethane (AOM)/dextran sulfate sodium salt (DSS), and highly enriched β-catenin hot spot mutations. SMAC deficiency also significantly increased the incidence of spontaneous intestinal polyps in APC(Min/+) mice. Loss of SMAC in mice led to elevated levels of cIAP1 and cIAP2, increased proliferation and activation of the NF-κB p65 subunit in normal and tumor tissues. Unexpectedly, SMAC deficiency had little effect on the incidence of precursor lesions, or apoptosis induced by AOM or DSS, or in established tumors in mice. Furthermore, SMAC knockout enhanced TNFα-mediated NF-κB activation via cIAP2 in HCT 116 colon cancer cells. These results demonstrate an essential and apoptosis-independent function of SMAC in tumor suppression and provide new insights into the biology and targeting of colon cancer.

A small molecule SMAC mimic LBW242 potentiates TRAIL- and anticancer drug-mediated cell death of ovarian cancer cells

Background

Ovarian cancer remains a leading cause of death in women and development of new therapies is essential. Second mitochondria derived activator of caspase (SMAC) has been described to sensitize for apoptosis. We have explored the pro-apoptotic activity of LBW242, a mimic of SMAC/DIABLO, on ovarian cancer cell lines (A2780 cells and its chemoresistant derivative A2780/ADR, SKOV3 and HEY cells) and in primary ovarian cancer cells. The effects of LBW242 on ovarian cancer cell lines and primary ovarian cancer cells was determined by cell proliferation, apoptosis and biochemical assays.

Principal Findings

LBW242 added alone elicited only a moderate pro-apoptotic effect; however, it strongly synergizes with tumor necrosis factor-related apoptosis inducing ligand (TRAIL) or anticancer drugs in inducing apoptosis of both ovarian cancer cell lines and primary ovarian cancer cells. Mechanistic studies show that LBW242-induced apoptosis in ovarian cancer cells is associated with activation of caspase-8. In line with this mechanism, c-FLIP overexpression inhibits LBW242-mediated apoptosis.

Conclusion

LBW242 sensitizes ovarian cancer cells to the antitumor effects of TRAIL and anticancer drugs commonly used in clinic. These observations suggest that the SMAC/DIABLO mimic LBW242 could be of value for the development of experimental strategies for treatment of ovarian cancer.