Chemoresistance Mechanisms in Non-Small Cell Lung Cancer-Opportunities for Drug Repurposing

Globally, lung cancer contributes significantly to the public health burden-associated mortality. As this form of cancer is insidious in nature, there is an inevitable diagnostic delay leading to chronic tumor development. Non-small cell lung cancer (NSCLC) constitutes 80-85% of all lung cancer cases, making this neoplasia form a prevalent subset of lung carcinoma. One of the most vital aspects for proper diagnosis, prognosis, and adequate therapy is the precise classification of non-small cell lung cancer based on biomarker expression profiling. This form of biomarker profiling has provided opportunities for improvements in patient stratification, mechanistic insights, and probable druggable targets. However, numerous patients have exhibited numerous toxic side effects, tumor relapse, and development of therapy-based chemoresistance. As a result of these exacting situations, there is a dire need for efficient and effective new cancer therapeutics. De novo drug development approach is a costly and tedious endeavor, with an increased attrition rate, attributed, in part, to toxicity-related issues. Drug repurposing, on the other hand, when combined with computer-assisted systems biology approach, provides alternatives to the discovery of new, efficacious, and safe drugs. Therefore, in this review, we focus on a comparison of the conventional therapy-based chemoresistance mechanisms with the repurposed anti-cancer drugs from three different classes-anti-parasitic, anti-depressants, and anti-psychotics for cancer treatment with a primary focus on NSCLC therapeutics. Certainly, amalgamating these novel therapeutic approaches with that of the conventional drug regimen in NSCLC-affected patients will possibly complement/synergize the existing therapeutic modalities. This approach has tremendous translational significance, since it can combat drug resistance and cytotoxicity-based side effects and provides a relatively new strategy for possible application in therapy of individuals with NSCLC.

SMAC Mimetics for the Treatment of Lung Carcinoma: Present Development and Future Prospects

BACKGROUND

Uncontrolled cell growth and proliferation, which originate from lung tissue often lead to lung carcinoma and are more likely due to smoking as well as inhaled environmental toxins. It is widely recognized that tumour cells evade the ability of natural programmed death (apoptosis) and facilitates tumour progression and metastasis. Therefore investigating and targeting the apoptosis pathway is being utilized as one of the best approaches for decades.

OBJECTIVE

This review describes the emergence of SMAC mimetic drugs as a treatment approach, its possibilities to synergize the response along with current limitations as well as future perspective therapy for lung cancer.

METHOD

Articles were analysed using search engines and databases namely Pubmed and Scopus.

RESULT

Under cancerous circumstances, the level of Inhibitor of Apoptosis Proteins (IAPs) gets elevated, which suppresses the pathway of programmed cell death, plus supports the proliferation of lung cancer. As it is a major apoptosis regulator, natural drugs that imitate the IAP antagonistic response like SMAC mimetic agents/Diablo have been identified to trigger cell death. SMAC i.e. second mitochondria activators of caspases is a molecule produced by mitochondria, stimulates apoptosis by neutralizing/inhibiting IAP and prevents its potential responsible for the activation of caspases. Various preclinical data have proven that these agents elicit the death of lung tumour cells. Apart from inducing apoptosis, these also sensitize the cancer cells toward other effective anticancer approaches like chemo, radio, or immunotherapies. There are many SMAC mimetic agents such as birinapant, BV-6, LCL161, and JP 1201, which have been identified for diagnosis as well as treatment purposes in lung cancer and are also under clinical investigation.

CONCLUSION

SMAC mimetics acts in a restorative way in the prevention of lung cancer.

The roles of E3 ubiquitin ligases in cancer progression and targeted therapy

Ubiquitination is one of the most important post-translational modifications which plays a significant role in conserving the homeostasis of cellular proteins. In the ubiquitination process, ubiquitin is conjugated to target protein substrates for degradation, translocation or activation, dysregulation of which is linked to several diseases including various types of cancers. E3 ubiquitin ligases are regarded as the most influential ubiquitin enzyme owing to their ability to select, bind and recruit target substrates for ubiquitination. In particular, E3 ligases are pivotal in the cancer hallmarks pathways where they serve as tumour promoters or suppressors. The specificity of E3 ligases coupled with their implication in cancer hallmarks engendered the development of compounds that specifically target E3 ligases for cancer therapy. In this review, we highlight the role of E3 ligases in cancer hallmarks such as sustained proliferation via cell cycle progression, immune evasion and tumour promoting inflammation, and in the evasion of apoptosis. In addition, we summarise the application and the role of small compounds that target E3 ligases for cancer treatment along with the significance of targeting E3 ligases as potential cancer therapy.

TRAF6 Promoted Tumor Glycolysis in Non-Small-Cell Lung Cancer by Activating the Akt-HIFα Pathway

TRAF6 has been reported to be associated with poor prognosis in non-small-cell lung cancer (NSCLC). However, its precise role in tumor development has not been elaborated. In the present study, the function and the mechanism by which TRAF6 contributes to development were intensively investigated. TRAF6 was found to be overexpressed in primary NSCLC tumor tissue and all tested cell lines. Knockdown of TRAF6 with shRNA substantially attenuated NSCLC cell proliferation and anchorage-independent growth. Moreover, tumor glycolysis, such as glucose consumption and lactate production, also significantly impaired. In TRAF6-deficient cells, hexokinase-2 expression was significantly reduced, which was caused by the decrease of HIF-1α transcriptional activity. Further investigations demonstrated that TRAF6 played an important role in the regulation of Akt activation, and exogenous overexpression of constitutively activated Akt substantially rescued glycolysis suppression in TRAF6 knockdown cells. The results of the xenograft model confirmed that downregulation of TRAF6 in NSCLC tumor cells dramatically restrained tumor growth in vivo. Taken together, our studies revealed the mechanism by which TRAF6 exerts its role in NSCLC development and suggested TRAF6 maybe was a promising candidate target for lung cancer prevention and therapy.

Identification of a new TRAF6 inhibitor for the treatment of hepatocellular carcinoma

Tumor necrosis factor (TNF) receptor-associated factor 6 (TRAF6) is an E3 ubiquitin ligase that plays a crucial role in signal transduction. Previous studies have demonstrated that TRAF6 is overexpressed in hepatocellular carcinoma (HCC) and that TRAF6 knockdown dramatically attenuates tumor cell growth. Thus, TRAF6 may represent a potential therapeutic target for the treatment of HCC. Herein, we identified bis (4-hydroxy-3,5-dimethylphenyl) sulfone (TMBPS) as a novel inhibitor that can directly bind to and downregulate the level of TRAF6. In vitro experimental results showed that TMBPS arrests the cell cycle in the G2/M phase by inactivating the protein kinase B (AKT) and extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathways and induces apoptosis by activating the p38/mitogen-activated protein kinase (MAPK) signaling pathway. In addition, TMBPS exhibited significant tumor growth inhibition in mouse xenograft models. In summary, our findings offer a proof-of-concept for the use of TMBPS as a novel chemotherapy drug for the prevention or treatment of HCC.

miR-146a-5p Plays an Oncogenic Role in NSCLC via Suppression of TRAF6

Non-small cell lung cancer (NSCLC) is the most deadly cancer in the world due to its often delayed diagnosis. Identification of biomarkers with high sensitivity, specificity, and accessibility for early detection, such as circulating microRNAs, is therefore of utmost importance. In the present study, we identified a significantly higher expression of miR-146a-5p in the serum and tissue samples of NSCLC patients than that of the healthy controls. In parallel, miR-146a-5p was also highly expressed in three human NSCLC adenocarcinoma-cell lines (A549, H1299, and H1975) compared to the human bronchial epithelium cell line (HBE). By dual-luciferase reporter assay and manipulation of the expressions of miR-146a-5p and its target gene, tumor necrosis factor receptor-associated factor 6 (TRAF6), we showed that the functional effects of miR-146a-5p on NSCLC cell survival and migration were mediated by direct binding to and suppression of TRAF6. Overexpression of TRAF6 sufficiently reversed miR-146a-5p-induced cancer cell proliferation, migration, and apoptosis resistance. Our data implied that miR-146a-5p/TRAF6/NF-κB-p65 axis could be a promising diagnostic marker and a therapeutic target for NSCLC.

TRAF6 promotes the progression and growth of colorectal cancer through nuclear shuttle regulation NF-kB/c-jun signaling pathway

AIMS

TRAF6 is an intracellular signal adapter molecule plays a significant role in tumor development. However, the specific mechanism causes and promotes of colorectal cancer keep largely unknown. Therefore, we sought to investigate the roles and the molecular mechanisms of TRAF6 in regulation colorectal cancer.

MATERIAL AND METHODS

The immunohistochemistry analyzed the expression of TRAF6 in colorectal cancer samples and analyzed the effects of expression of TRAF6 on the prognosis in colorectal cancer. The roles of TRAF6 in regulating colorectal cancer cell proliferation, colony formation, cell migration, cell wound healing and cell invasion were evaluated in vitro. Animal studies were performed to investigate the effects of TRAF6 on tumor growth. mRNA abundance of key genes was analyzed via qPCR. Protein level of TRAF6 and NF-κB/AP-1 signaling pathways was examined by Western blot. Luciferase reporter and Immunofluorescence assays were used to identify the activities NF-κB/AP-1 signaling pathways.

KEY FINDINGS

TRAF6 high expression in colorectal cancer tissues. And colorectal cancer patients with high expression of TRAF6 had a poor survival rate. TRAF6 knockdown can inhibit proliferation, migration, and invasion of colorectal cancer cells in vitro and in vivo experiments. TRAF6 activates the TRAF6-NF-κB/AP-1 signaling pathway by entering the nucleus, causing biobehavioral changes in colorectal cancer cells.

SIGNIFICANCE

TRAF6 plays a vital role in the progression of colorectal cancer. What's more, research elucidating the biological mechanisms of TRAF6 can treated as potential therapeutic target for colorectal cancer.

In vitro and in vivo cancer cell apoptosis triggered by competitive binding of Cinchona alkaloids to the RING domain of TRAF6

TRAF6 is highly expressed in many tumors and plays an important role in the immune system. The aim of this study is to confirm anti-tumor activities of all naturally occurring Cinchona alkaloids that have been screened using computational docking program, and to validate the accuracy and specificity of the RING domain of TRAF6 as a potential anti-tumor target, and to explore their effect on the immune system. Results reported herein would demonstrate that Cinchona alkaloids could induce apoptosis in HeLa cells, inhibit the ubiquitination and phosphorylation of both AKT and TAK1, and up-regulate the ratio of Bax/Bcl-2. In addition, these compounds could induce apoptosis in vivo, and increase the secretion of TNF-α, IFN-γ, and IgG, while not significantly impacting the ratio of CD4+T/CD8+T. These investigations suggest that the RING domain of TRAF6 could serve as a de novo biological target for therapeutic treatment in cancers.

miR‑146a‑5p targets TCSF and influences cell growth and apoptosis to repress NSCLC progression

Several studies have indicated that microRNAs (miRs) mediate multiple pathways associated with tumorigenesis and progression. Our preliminary study experimentally verified that miR-146a-5p has a role in the biological behavior of non-small cell lung cancer (NSCLC) cells. To perform further investigation of miR-146a-5p, the present study evaluated miR-146a-5p by targeting its downstream gene tumor collagenase stimulatory factor (TCSF) to influence cell viability, proliferation and apoptosis in NSCLC. Online sequence prediction, a thorough search of the open source database The Cancer Genome Atlas (TCGA), immunohistochemistry (IHC) of TCSF in clinical lung cancer tissues, and a dual-luciferase assay, as well as assays to test viability, proliferation and apoptosis in vitro, were conducted to explain the targeted regulation association between miR-146a-5p and TCSF in NSCLC. The miRanda and TargetScanHuman database revealed that TCSF and miR-146a-5p had target binding sites. A luciferase reporter assay demonstrated that miR-146a-5p and TCSF did have complementary sequences (P<0.05). From the TCGA database, TCSF was highly expressed in lung adenocarcinoma and lung squamous cell carcinoma tissues when compared with normal lung tissues (P<0.05). Furthermore, the protein level of TCSF in cancerous lung tissues was determined by IHC, and it was concluded that TCSF protein was also upregulated in NSCLC tissues (P<0.001). A significant difference was identified following in vitro experiments for the NSCLC cell line A549, which revealed that miR-146a-5p and TCSF regulated cell viability, proliferation and apoptosis. In conclusion, the present study verified the target action association between TCSF and miR-146a-5p with high throughput data analysis and experimental results in NSCLC.

Emodin suppresses angiogenesis and metastasis in anaplastic thyroid cancer by affecting TRAF6‑mediated pathways in vivo and in vitro

Emodin has been recognized to be an anti‑cancer agent against a number of types of human cancer. It was demonstrated that TNF receptor‑associated factor 6 (TRAF6) was correlated with cancer angiogenesis and metastasis. The present study confirmed the association between TRAF6 and the angiogenesis/metastasis of anaplastic thyroid cancer (ATC). The anti‑angiogenesis and metastatic effects of emodin, in addition to its molecular mechanisms in ATC, were investigated. A total of two ATC cell lines, namely 8505c and SW1736, were studied. ATC cells were implanted into nude mice to form xenografts or to establish lung metastasis models. Emodin was used to incubate ATC cells or to treat animals orally. An MTT assay was used to assess cell proliferation. A wound healing assay was employed to evaluate cell migration. ELISA analysis was used to detect the vascular endothelial growth factor (VEGF) content. Western blotting was used to determine the protein expression levels. In the in vivo study, cancer angiogenesis was assessed by micro vascular density measurement. The lung metastatic rate was the criterion for cancer metastasis. The results of the present study demonstrated that the proliferation of ATC was inhibited by emodin. The activation of the TRAF6/hypoxia inducible factor (HIF)‑1α/VEGF and TRAF6/basigin (CD147)/matrix metalloproteinase‑9 (MMP9) pathways were associated with the angiogenesis and metastasis of ATC. In a concentration‑dependent manner, emodin inhibited the TRAF6/HIF‑1α/VEGF and TRAF6/CD147/MMP9 signaling pathways to suppress angiogenesis and metastasis. In conclusion, emodin exerted anti‑angiogenic and anti‑metastatic activities in ATC by affecting TRAF6‑mediated pathways.

Clinical significance and effect of AEG-1 on the proliferation, invasion, and migration of NSCLC: a study based on immunohistochemistry, TCGA, bioinformatics, in vitro and in vivo verification

Background

Astrocyte elevated gene-1 (AEG-1) is related to the tumorigenesis and deterioration of different cancers, including non-small cell lung cancer (NSCLC). However, the effect of AEG-1 in NSCLC remains unclear. In this study, we aimed to investigate the clinical significance and effect of AEG-1 on biological function of NSCLC.

Results

AEG-1 was significantly overexpressed in NSCLC tissues and closely correlated to the deterioration of NSCLC based on tissue microarray, TCGA database and meta-analysis. After knock-down of AEG-1, the proliferation, migration and invasion of NSCLC cells were all inhibited, and the tumorigenic and angiogenic ability of NSCLC cells were weakened. Furthermore, the AEG-1 co-expressed genes were significantly related to AMPK signaling pathway based on bioinformatics approaches.

Materials and Methods

A tissue microarray, the Cancer Genome Atlas (TCGA) database, as well as a meta-analysis were performed to analyze the relationship between AEG-1 and the clinicopathological parameters of NSCLC. Furthermore, immunocytochemistry, Western blot analysis, scratch assay, colony formation assay, Transwell migration and invasion assay and the chick embryo chorioallantoic membrane (CAM) model were conducted to explore the effect of AEG-1 on NSCLC in vitro and in vivo. Additionally, bioinformatics analyses were carried out to assess the potential pathways and networks of the co-expressed genes of AEG-1.

Conclusions

AEG-1 is positively activated in the tumorigenesis and deterioration of NSCLC. We hypothesize that AEG-1 could play an important role in NSCLC via AMPK signaling pathway. Inhibiting the expression of AEG-1 is expected to become a novel method in the therapeutic strategies of NSCLC.

Cinchonine induces apoptosis of HeLa and A549 cells through targeting TRAF6

BACKGROUND

Cancer cells are known to over-express TRAF6 that is critical for both AKT and TAK1 activations. The Really Interesting New Gene (RING) domain of TRAF6 is believed to be responsible for the E3 ligase activity, ZINC fingers of TRAF6 provide critical support for the activity of the RING domain which is critical for both AKT and TAK1 activations.

METHODS

We employed computational docking program to identify small molecules that could effectively and competitively bind with the RING domain of TRAF6, which is believed to be responsible for its E3 ligase activity. MTT assay and flow cytometry were employed to analyze apoptosis of cancer cells. Signaling pathways were detected using immunoprecipitation and western blotting, and immunofluorescence was pursued to assess the nature of binding of cinchonine to TRAF6. We also performed animal experiments to test effect of cinchonine in vivo.

RESULTS

Cinchonine, a naturally occurring Cinchona alkaloid identified from the docking study, could bind to TRAF6 in HeLa and A549 cells and induce apoptosis of these cancer cells. We found that AKT ubiquitination and phosphorylation as well as phosphorylation of TAK1 were decreased. These activities would lead to subsequent suppression anti-apoptotic protein Bcl-2, while elevating pro-apoptotic protein Bax. Immunofluorescence staining unambiguously demonstrated the binding of cinchonine specifically at the RING domain of TRAF6 in cells, thereby validating the computational modeling. Animal experiments showed that cinchonine could suppress tumor growth in mice without showing significant acute toxicity.

CONCLUSION

These investigations suggest that through competitive binding with the RING domain of TRAF6, cinchonine could induce apoptosis via inhibiting AKT and TAK1 signaling pathways.

Relationship between TRAF6 and deterioration of HCC: an immunohistochemical and in vitro study

Objective

To explore the relationship between tumor necrosis factor receptor-associated factor 6 (TRAF6) and the clinicopathological features in HCC as well as its biological function.

Methods

Totally, 412 liver tissues were collected, including 171 hepatocellular carcinoma (HCC) and their corresponding non-tumor tissues, 37 cirrhosis and 33 normal liver tissues. The expression of TRAF6 was assessed by immunohistochemistry. Then, analysis of the correlations between TRAF6 expression and clinicopathological parameters in HCC was conducted. Furtherer, in vitro experiments on HepG2 and Hep3B cells were performed to validate the biological function of TRAF6 on HCC cells. TRAF6 siRNA was transfected into HepG2 and Hep3B cell lines and TRAF6 expression was evaluated with RT-qPCR and western blot. The assays of cell viability, proliferation, apoptosis and caspase-3/7 activity were carried out to investigate the effects of TRAF6 on HCC cells with RNA interference. Cell viability was assessed with Cell Titer-Blue kit. Cell proliferation was tested with MTS kit. Cell apoptosis was checked through morphologic detection with fluorescence microscope, as well as caspase-3/7 activity was measured with fluorogenic substrate detection.

Results

The positive expression rate of TRAF6 protein was 49.7 % in HCC, significantly higher than that of normal liver (12.1 %), cirrhosis (21.6 %) and adjacent non-cancerous tissues (36.3 %, all P < 0.05). Upregulated TRAF6 was detected in groups with metastasis (Z = −2.058, P = 0.04) and with low micro-vessel density (MVD) expression (Z = −2.813, P = 0.005). Spearman correlation analysis further showed that the expression of TRAF6 was positively correlated with distant metastasis (r = 0.158, P = 0.039) and negatively associated with MVD (r = −0.249, P = 0.004). Besides, knock-down of TRAF6 mRNA in HCC cell lines HepG2 and Hep3B both resulted in cell viability and proliferation inhibition, also cell apoptosis induction and caspase-3/7 activity activation.

Conclusions

TRAF6 may contribute to metastasis and deterioration of the HCC via influencing cell growth and apoptosis. Thus, TRAF6 might become a predictive and therapeutic biomarker for HCC.

Clinicopathological significance of STAT4 in hepatocellular carcinoma and its effect on cell growth and apoptosis

Background

Recent studies showed that signal transducer and activator of transcription 4 (STAT4) was downregulated in hepatocellular carcinoma (HCC) tissues. However, the role of STAT4 in HCC is still unknown. The aim of this study is to explore the association between STAT4 expression and other clinicopathological features in HCC and to test the effect of STAT4 on cell growth and apoptosis in vitro.

Methods

STAT4 was evaluated by immunohistochemistry in 171 HCC and corresponding paraneoplastic liver, 37 cirrhosis, and 33 normal liver tissues. Association between STAT4 and clinicopathological parameters was analyzed. Meta-analysis on STAT4 in cancer was performed. The effect of STAT4 small interfering RNA (siRNA) on cell growth and cell apoptosis was also detected.

Results

Positive rate of STAT4 was 29.2% (50/171) in HCC tissues, 53.2% (91/171) in paraneoplastic liver tissues, 64.9% (24/37) in cirrhosis tissues, and 72.7% (24/33) in normal liver tissues. STAT4 was upregulated in younger patients who were female, with single tumor node, early TNM stage, without portal vein tumor embolus, and α-fetoprotein (AFP)-positive tumors compared with the groups comprising older patients, males, and those with multiple tumor nodes, advanced TNM stage, with portal vein tumor embolus, and AFP negative tumors. Meta-analysis showed STAT4 was correlated with TNM stage (OR =0.50, 95% CI =0.30, 0.83, P=0.008) and age (OR =0.58, 95% CI =0.38, 0.95, P=0.032) in malignant tissues, and with AFP level (OR =1.76, 95% CI =1.06, 2.94, P=0.03) in HCC. STAT4 siRNA promoted growth and suppressed apoptosis of HepG2 cells.

Conclusion

STAT4 might play a vital role in development of HCC, via influencing cell growth and apoptosis, as a tumor suppressor.

siRNA-induced TRAF6 knockdown promotes the apoptosis and inhibits the invasion of human lung cancer SPC-A1 cells

Tumor necrosis factor receptor-associated factor 6 (TRAF6) has been found to be involved in multiple cancers. However, the effect of small interfering RNA (siRNA)-induced knockdown of TRAF6 on the biological behaviors of cancer cells remains unknown. Thus, the present study aimed to investigate the effect of siRNA-induced knockdown of TRAF6 on the biological behaviors of human lung cancer SPC-A1 cells. The expression of TRAF6 was determined in human lung adenocarcinoma A549, non-small cell lung cancer H1650, human airway epithelial Calu-3 and human lung cancer SPC-A1 cell lines using quantitative RT-PCR (qRT-PCR) and western blotting at the transcriptional and translational levels. TRAF6 expression was knocked down in the SPC-A1 cells using an siRNA technique, and the effects of TRAF6 knockdown on NF-κB activity, cell proliferation, apoptosis, cell cycle, invasion and migration of the SPC-A1 cells were determined using electrophoretic mobility shift assay (EMSA), cell proliferation assay, flow cytometry, Transwell invasion assay and scratch wound assay. In addition, the protein expression of CD24, CXCR4, MMP1, MMP2, MMP9, TWIST, TIMP-2 and Slug was quantified using western blotting assay. Western blotting and qRT-PCR assays showed upregulation of TRAF6 at both the translational and transcriptional levels in the Calu-3 and SPC-A1 cells, and K63-linked ubiquitination of TRAF6 and constitutive NF-κB activation were detected in the SPC-A1 cells. Knockdown of TRAF6 inhibited the migration and invasion and promoted the apoptosis of the SPC-A1 cells, but had little effect on cell proliferation and the cell cycle. In addition, siRNA-induced TRAF6 knockdown caused a marked reduction in the protein expression of CD24 and CXCR4, but had little effect on MMP-1, MMP-2, MMP-9, Twist, TIMP-2 or Slug expression. The present study demonstrated that TRAF6 is upregulated in human lung cancer cells, and siRNA-induced TRAF6 knockdown inhibits the invasion of lung cancer cells and promotes apoptosis. It is suggested that TRAF6 may be a promising target for the therapy of lung cancer.