The Neem Limonoid Nimbolide Modulates Key Components of the DNA Damage Response Signalling in Cellular and Animal Models of Oral Squamous Cell Carcinoma

BACKGROUND

Deregulated DNA damage response (DDR) network is implicated in cancer progression and therapy resistance.

OBJECTIVE

The present study was designed to investigate whether nimbolide, an anticancer neem limonoid, targets key components of the DDR signalling pathway in cellular and animal models of oral squamous cell carcinoma (OSCC).

METHODS

OSCC cells (SCC-4 and SCC-9), 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinoma model, chemoresistant OSCC patient-derived xenograft (PDX) model established in athymic nude mice, and tissue sections from patients with oral premalignant/malignant disease were used for the study. Key molecules that orchestrate the DDR, including the MRN complex, ATM, DNA-PKcs, H2AX, and p53, were analysed by qRT-PCR, immunoblotting, immunofluorescence, and immunohistochemistry. Cell proliferation and apoptosis indices were evaluated.

RESULTS

Nimbolide significantly reduced 8-oxodG levels, expression of MRN, ATMS1891, and γ-H2AX, with an increase in p-p53S15 in OSCC cells as well as in the HBP model. Nimbolide potentiated the effect of KU-55933 in ATM inhibition. In the PDX model, nimbolide suppressed tumor formation, stimulated DDR and apoptosis, inhibited cell proliferation, and enhanced sensitivity to cisplatin. Analysis of p-ATM expression revealed a significant increase during the sequential progression of hamster and human OSCC.

CONCLUSIONS

This study provides compelling evidence that nimbolide functions as a DDR inhibitor in cellular and hamster OSCC models and as a DDR activator in the PDX model primarily by targeting ATM. Small molecules like nimbolide that modulate DDR are of immense benefit in cancer therapy. The study has also unveiled p-ATM as a promising biomarker of tumour progression in human OSCCs.

Limonoids from neem (Azadirachta indica A. Juss.) are potential anticancer drug candidates

Neem (Azadirachta indica A. Juss.), a versatile evergreen tree recognized for its ethnopharmacological value, is a rich source of limonoids of the triterpenoid class, endowed with potent medicinal properties. Extracts of neem have been documented to display anticancer effects in diverse malignant cell lines as well as in preclinical animal models that has largely been attributed to the constituent limonoids. Of late, neem limonoids have become the cynosure of research attention as potential candidate agents for cancer prevention and therapy. Among the various limonoids found in neem, azadirachtin, epoxyazadiradione, gedunin, and nimbolide, have been extensively investigated for anticancer activity. Azadirachtin, a potent biodegradable pesticide, exhibits profound antiproliferative effects by preventing mitotic spindle formation and cell division. The antiproliferative activity of gedunin has been demonstrated to be mediated primarily via inhibition of heat shock protein90 and its client proteins. Epoxyazadiradione inhibits pro-inflammatory and kinase-driven signaling pathways to block tumorigenesis. Nimbolide, the most potent cytotoxic neem limonoid, inhibits the growth of cancer cells by regulating the phosphorylation of keystone kinases that drive oncogenic signaling besides modulating the epigenome. There is overwhelming evidence to indicate that neem limonoids exert anticancer effects by preventing the acquisition of hallmark traits of cancer, such as cell proliferation, apoptosis evasion, inflammation, invasion, angiogenesis, and drug resistance. Neem limonoids are value additions to the armamentarium of natural compounds that target aberrant oncogenic signaling to inhibit cancer development and progression.

Crosstalk between PD-L1 and Jak2-Stat3/ MAPK-AP1 signaling promotes oral cancer progression, invasion and therapy resistance

BACKGROUND

Programmed cell death ligand-1 (PD-L1)is an antitumor immunity molecule and a great target to cure oral cancer; nonetheless, the limited success can be attributed to many complex pathways and tumor-related interferences.

METHODS

In the present study, 150 human oral squamous cell carcinoma (OSCC) tissue samples, including 17 adjacent normals, 56 primary tumors, 47 invasive tumors, and 30 therapy-resistant (RT) samples, were included. The parental/cisplatin-resistant (CisR-SCC4/9) cells were utilized for overexpression (Jak1-3 wild type and catalytically inactive), knockdown (PD-L1 siRNA), targeting MAPK/PI3K/Jak-Stat pathways (SMIs) and checking microsomes. The expression of PD-L1, transcription factors (TFs), signaling pathways, survival/apoptosis, therapy resistance, and invasiveness-related molecules/their activity were determined by RT-PCR, Immunohistochemistry, Western blot, Gelatin Zymography, and MTT assay.

RESULTS

Advanced OSCC tumors (invasive and drug-resistance), CisR-SCC4/9 cells, and secretory exosomes (CisR-SCC4/9) were found with increased PD-L1 expression. PD-L1 mRNA/protein showed a positive correlation with different TFs (AP1 > Stat3 > c-myc > NFκB) in tumor samples. The PD-L1 expression was more influenced by Jak-Stat/ MAPK-AP1 pathways over PI3K. The ectopic expression of Jak1-3 suggests Jak2 inducted PD-L1 level over Jak1/Jak3. Finally, PD-L1 directly supports survival (Bcl-xL, Bax, cleaved caspase-3), invasion (MMP2/9), and drug-resistance (ALDH-1A1/-3A1) program in OSCC through its link with several molecules.

CONCLUSIONS

PD-L1 was regulated mainly by the Jak2-Stat3/ MAPK-AP1 pathway, and besides the routine immunological functions, it supports OSCC survival, invasion, and therapy resistance. PD-L1 can be used as an indicator of severity and can be targeted along with Jak2-Stat3/ MAPK-AP1 for a better outcome OSCC.

Obesity Associated with Prediabetes Increases the Risk of Breast Cancer Development and Progression-A Study on an Obese Rat Model with Impaired Glucose Tolerance

Patients with comorbidities of obesity and diabetes are recognized to be at high risk of breast cancer development and face worse breast cancer outcomes. Though several reports showed the reinforced link between obesity, diabetes, and prediabetes with breast cancer, the underlying molecular mechanisms are still unknown. The present study aimed to investigate the underlying molecular link between increased risks of breast cancer due to coincident diabetes or obesity using a spontaneous obese rat model with impaired glucose tolerance (WNIN/GR-Ob rat). A single dose of solubilized DMBA suspension (40 mg/kg body weight) was orally administered to the animals at the age of 60 days to induce breast tumors. The tumor incidence, latency period, tumor frequency, and tumor volume were measured. Histology, immunohistochemistry, and immunoblotting were performed to evaluate the tumor morphology and expression levels of signal molecules. The development of mammary tumors in GR-Ob rats was characterized by early onset and shorter latency periods compared to control lean rats. While 62% of obese rats developed breast tumors, tumor development in lean rats was only 21%. Overexpression of ER, PR, Ki67, and p53 markers was observed in tumor tissues of obese rats in comparison with lean rats. The levels of the hallmarks of cell proliferation and angiogenesis involved in IGF-1/PI3K/Akt/GSK3β/β-catenin signaling pathway molecules were upregulated in obese rat breast tumors compared to lean rats. Furthermore, obesity with prediabetes is associated with changes in IGF-1 signaling and acts on PI3K/Akt/GSK3β/β-catenin signaling, which results in rapid cell proliferation and development of breast tumors in obese rats than the lean rats. These results indicate that tumor onset and development were faster in spontaneous obese rat models with impaired glucose tolerance than in their lean counterparts.

Role and regulation of GLUT1/3 during oral cancer progression and therapy resistance

OBJECTIVE

This study aimed to determine whether glucose transporter-1/3 (GLUT1/3) increased expression could contribute to oral tumor severity. Furthermore, this study detected whether GLUT1/3 mRNA/protein was associated with oncogenic transcription factors (HIF1α, AP1 and NFκB) and whether by blocking GLUT1 along with cisplatin could sensitize drug-resistant OSCC cells.

DESIGN

We used 120 post-operated human tissue samples, including 35 primary tumors (PT), 43 invasive tumors (N1-3), 17 recurrent chemoradiation-resistant tumors (RCRT), and 25 PT-adjacent normal tissues (AN). The cisplatin-resistant (CisR-SCC4/9) cells were generated using a drug escalation strategy from parental SCC4/9 cells. The BAY-876 treatment blocked GLUT1 in OSCC cells. Western Blot, Immunohistochemistry, and reverse transcription polymerase chain reaction (RT-PCR) were used to detect various proteins and mRNA. Cell survival was determined by MTT assay.

RESULTS

GLUT1/3 expression was observed more in PT over AN tissue (PT > AN), N1-3 > PT, and .RCRT > PT. GLUT1 expression was maximum in the RCRT group and CisR-SCC4/9 cells over their parental counterpart, linked with tumor size (p=0.0037) and loco-regional invasiveness (p=0.0422). GLUT1/3 mRNA/protein was correlated (positively) with oncogenic transcription factors (TFs) like HIF1α, AP1 and NFκB. We found the degree of positive correlation of these TFs with GLUT1/3 was in the order c-Jun > HIF1α > Fra-2 > NFκB > c-Fos. Treatment of BAY-876 and cisplatin-induced cell death in both CisR-SCC4/9 cells, possibly by triggering apoptosis and autophagy.

CONCLUSION

Collectively, our results demonstrated increased GLUT1/3 overexpression linked with oral tumor severity like invasion and therapy resistance, and it was powered mainly by c-Jun (AP1). Blocking GLUT1 receptors and cisplatin application can sensitize CisR-OSCC cells.

Utility of Prostate-Specific Antigen Isoforms and Prostate Health Index in the Diagnosis of Metastatic Prostate Cancer

Objective The current study was undertaken to investigate the utility of total prostate-specific antigen (tPSA), its isoform [-2] proPSA (p2PSA), and prostate health index (PHI) in the diagnosis of metastatic prostate cancer (PCa).

Materials and Methods This study was conducted from March 2016 to May 2019. Eighty-five subjects who were diagnosed with PCa for the first time, following transrectal ultrasound-guided prostate biopsy, were included in the study. The prebiopsy blood samples were analyzed in Beckman Coulter Access-2 Immunoanalyzer for tPSA, p2PSA, and free PSA (fPSA), and the calculated parameters included %p2PSA, %fPSA, and PHI. Mann–Whitney's U test was used as test of significance, and p-value less than 0.05 was considered statistically significant.

Results Of the 85 participants, 81.2% (n = 69) had evidence of metastasis, both clinically and pathologically. The median tPSA (ng/mL), p2PSA (pg/mL), %p2PSA, and PHI were significantly higher in the group with evidence of metastasis (46.5 vs. 13.76; 198.0 vs. 35.72; 3.25 vs. 1.51; 237.58 vs. 59.74, respectively). The sensitivity (%), specificity (%), negative predictive value (%), and positive predictive value (%) to diagnose metastatic PCa of tPSA at a cutoff of 20 ng/mL, PHI at a cutoff of 55, and %p2PSA at a cutoff of 1.66 were 92.7, 98.5, and 94.2; 37.5, 43.7, and 62.5; 54.5, 87.5, and 71.4; and 86.4, 88.3, and 91.5, respectively.

Conclusion Using tests such as %p2PSA and PHI in the standard armamentarium for the diagnosis of metastatic PCa in addition to PSA will help in selecting the appropriate treatment strategy, including active surveillance.

A real-life decision-making problem with Hendecagonal fuzzy numbers

Making the correct decision in a real-time situation is extremely difficult. In today’s technological age, computational methods are available, and they may assist the company’s top leaders in making sound decisions and strengthening the organization. There are several techniques for dealing with decision-making problems, one of which is the use of Hendecagonal fuzzy numbers. These fuzzy numbers are used to represent the ambiguity or ambiguity of eleven linguistic variables. To address these shortcomings, we use the ranking method, relativity function, and comparison matrix to aid in decision-making because we have eleven constraints (linguistic variables) that can be expressed in a hendecagonal fuzzy number matrix (HdcgFNM). The raking technique, relativity function, and comparison matrix were evaluated using a case study.

Nimbolide, a Neem Limonoid, Inhibits Angiogenesis in Breast Cancer by Abrogating Aldose Reductase Mediated IGF-1/PI3K/Akt Signaling

Background & Objectives:

There is growing evidence to implicate the insulin/IGF-1R/PI3K/Akt signaling cascade in breast cancer development and the central role of aldose reductase (AR) in mediating the crosstalk between this pathway and angiogenesis. The current study was designed to investigate whether nimbolide, a neem limonoid, targets this oncogenic signaling network to prevent angiogenesis in breast cancer.

Methods:

Breast cancer cells (MCF-7, MDA-MB-231), EAhy926 endothelial cells, MDA-MB-231 xenografted nude mice, and tumour tissues from breast cancer patients were used for the study. Expression of AR and key players in IGF-1/PI3K/Akt signaling and angiogenesis was evaluated by qRT-PCR, immunoblotting, and immunohistochemistry. Molecular docking and simulation, overexpression, and knockdown experiments were performed to determine whether nimbolide targets AR and IGF-1R

Results:

Nimbolide inhibited AR with consequent blockade of the IGF-1/PI3K/Akt and HIF-1/VEGF signaling circuit by influencing the phosphorylation and intracellular localisation of key signaling molecules. Downregulation of DNMT-1, HDAC-6, miR-21, HOTAIR, and H19 with upregulation of miR-148a/miR-152 indicated that nimbolide regulates AR and IGF-1/PI3K/Akt signaling via epigenetic modifications. Coadministration of nimbolide with metformin and the chemotherapeutic drugs tamoxifen/cisplatin displayed higher efficacy than single agents in inhibiting IGF-1/PI3K/Akt/AR signaling. Grade-wise increases in IGF-1R and AR expression in breast cancer tissues underscore their value as biomarkers of progression.

Conclusions:

This study provides evidence for the anticancer effects of nimbolide in cellular and mouse models of breast cancer besides providing leads for new drug combinations. It has also opened up avenues for investigating potential molecules such as AR for therapeutic targeting of cancer.

Glycogen synthase kinase-3β inactivation promotes cervical cancer progression, invasion, and drug resistance

Human papillomavirus (HPV) infection-dependent cervical cancer is one of the most common gynecological cancers and often becomes aggressive, with rapid proliferation, invasion/migration, and drug resistance. Here, 135 fresh human cervical squamous cell carcinoma (CSCC) tissue specimens, comprising 21 adjacent normal (AN), 30 cervical intraepithelial neoplasia (CIN_1-3 ), 45 CSCC, and 39 drugs (chemo-radiation)-resistant cervical tumor (DRCT) tissues were included. HPV-positive (HeLa, SiHa), HPV-negative (C33A), and cisplatin-resistant (CisR-HeLa/-SiHa/-C33A) cell lines were used for in vitro studies. HPV16/18 oncoproteins E6/E7, pERK1/2, and glycogen synthase kinase-3 (GSK3) and the matrix metalloproteinases (MMPs) MMP-9/-2 were assessed using immunohistochemistry, WB, and gelatin zymography. HPV16/18 infection was observed in 16.7% of the CIN_1-3 , 77.8% of the CSCC, and 89.7% of DRCT samples. Total and inactive GSK3β expressions were associated with overall CSCC progression (p = 0.039 and p = 0.024, respectively) and chemoresistance (p = 0.004 and p = 0.014, respectively). Positive correlations were observed, between the expression of E6 and pGSK3β expression (p = 0.013); E6 and CSCC progression (p < 0.0001)/drug resistance (p = 0.0001). CisR-HeLa/-SiHa was more dependent on pGSK3β, and activation of GSK3 by SMIs (iAkt), treatment with nimbolide, or knockdown of E6/E7 reduced cisplatin resistance and promoted apoptosis. Hence, the activation of GSK3β with nimbolide and iAkt can be exploited for therapeutic interventions of cervical cancer.

Nimbolide, a Neem Limonoid, Is a Promising Candidate for the Anticancer Drug Arsenal

Nimbolide, a major limonoid constituent of Azadirachta indica, commonly known as neem, has attracted increasing research attention owing to its wide spectrum of pharmacological properties, predominantly anticancer activity. Nimbolide is reported to exert potent antiproliferative effects on a myriad cancer cell lines and chemotherapeutic efficacy in preclinical animal tumor models. The potentiality of nimbolide to circumvent multidrug resistance and aid in targeted protein degradation broaden its utility in enhancing therapeutic modalities and outcome. Accumulating evidence indicates that nimbolide prevents the acquisition of cancer hallmarks such as sustained proliferation, apoptosis evasion, invasion, angiogenesis, metastasis, and inflammation by modulating kinase-driven oncogenic signaling networks. Nimbolide has been demonstrated to abrogate aberrant activation of cellular signaling by influencing the subcellular localization of transcription factors and phosphorylation of kinases in addition to influencing the epigenome. Nimbolide, with its ever-expanding repertoire of molecular targets, is a valuable addition to the anticancer drug arsenal.

Activation of PI3K/Akt/NF-kB Signaling Mediates Swedish Snus Induced Proliferation and Apoptosis Evasion in the Rat Forestomach: Modulation by Blueberry

BACKGROUND AND OBJECTIVES

The present study was undertaken to ascertain whether the modulatory effects of blueberries on cell proliferation induced by Swedish snus in the rat forestomach epithelium is mediated via abrogation of the PI3K/Akt/NFκB signaling axis that regulates cell fate decision.

METHODS

The transcript and protein expression of genes involved in cell cycle progression and apoptosis, as well as canonical PI3K/Akt/NF-κB signaling pathways, were analyzed by qRT-PCR, immunoblotting and ELISA. Expression profiling of noncoding RNAs (ncRNAs) that influence PI3K/Akt/NF-κB signaling was undertaken. TUNEL assay was performed using flow cytometry.

RESULTS

Administration of snus induced basal cell hyperplasia in the rat forestomach with increased cell proliferation and inhibition of apoptosis. This was associated with the activation of PI3K/Akt/NFκB signaling. Coadministration of blueberries significantly suppressed snus-induced hyperplasia. Analysis of the molecular mechanisms revealed that blueberries suppress the phosphorylation of Akt, NF-κB and IKKβ, prevent nuclear translocation of NF-κB and modulate the expression of microRNAs that influence PI3K/Akt/NF-κB signaling.

CONCLUSION

Taken together, the results of the current study provide compelling evidence that blueberries exert significant protective effects against snus-induced soft tissue changes in the rat forestomach epithelium mediated by inhibiting key molecular players in the PI3K/Akt/NF-κB signaling axis. Long-term studies on the impact of snus exposure on various cellular processes, signaling pathways, and the interplay between genetic and epigenetic mechanisms are however warranted. The results of this investigation may contribute to the development of protection against soft tissue changes induced by smokeless tobacco in the human oral cavity.

Abstract 1165: Differential expression of CD44 variants drive the progression, invasion, drug-resistance and stemness characteristics in human oral squamous cell carcinoma

Purpose: Cluster of differentiation 44 (CD44) is a cell-surface glycoprotein and plays role in the progression and severity of oral squamous cell carcinoma (OSCC). Here we report differential function of CD44 variants in OSCC progression.

Materials and methods: The expression of CD44 standard (CD44s) and variants (CD44v4, CD44v6); the activation of signaling pathways (MAPK, PI3K); the cell viability; and the MMP-9/-2 activity were assessed using RT-PCR, immunohistochemistry, Western blotting, MTT assay and gelatin zymography. These experiments were carried out using fresh human OSCC tissue specimens, including adjacent normal, noninvasive (N0), invasive tumor samples (N1-3) and chemo-radiation resistant tumor samples (RCRT). We also used OSCC cell lines, including parental (SCC9/SCC4) and Cisplatin-resistant (CisR-SCC9/-SCC4) to confirm our observation with human tissues. Knock down of CD44 variants or inactivation of MAPK/PI3K pathways was achieved for in vitro analysis in OSCC cells.

Summary: Differential expressions of CD44 variants (v4and v6) were associated with overall oral cancer aggressiveness. CD44v4 expression was positively correlated with the activation of MAPK pathway causing chemoresistance. Conversely, CD44v6 expression and activation of PI3K-Akt caused invasiveness of OSCC. Finally, an overlapping role of two major signal transduction pathways such as MAPK and PI3K, that impinge on the variants/ isoforms expressions of a single gene i.e. CD44 that leads to the OSCC aggressiveness.

Conclusion: Collectively, these results established that CD44 variants (v4and v6) expression driven by MAPK/PI3K are associated with the overall progression, drug-resistance, invasion, and stemness characteristics leading to the aggressiveness of OSCC. Hence targeting these pathways may be exploited for treating OSCC.

Keywords: OSCC, CD44s, CD44v4/6, MAPK, PI3K, Notch, Chemoresistance, Invasion/migration, stemness, aggressiveness of OSCC.

Note: This abstract was not presented at the meeting.

Citation Format: Tanushree Kashyap, Siddavaram Nagini, Ajay Rana, Rajakishore Mishra. Differential expression of CD44 variants drive the progression, invasion, drug-resistance and stemness characteristics in human oral squamous cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1165.

Cytochrome P450 Structure, Function and Clinical Significance: A Review

BACKGROUND

The cytochrome P450 (CYP) enzymes are membrane-bound hemoproteins that play a pivotal role in the detoxification of xenobiotics, cellular metabolism and homeostasis. Induction or inhibition of CYP enzymes is a major mechanism that underlies drug-drug interactions. CYP enzymes can be transcriptionally activated by various xenobiotics and endogenous substrates through receptor-dependent mechanisms. CYP enzyme inhibition is a principal mechanism for metabolism- based drug-drug interactions. Many chemotherapeutic drugs can cause drug interactions due to their ability to either inhibit or induce the CYP enzyme system. Predictions based on in silico analyses followed by validation have identified several microRNAs that regulate CYPs. Genetic polymorphisms and epigenetic changes in CYP genes may be responsible for inter-individual and interethnic variations in disease susceptibility and the therapeutic efficacy of drugs.

OBJECTIVE

The present review is a comprehensive compilation of cytochrome P450 structure, function, pharmacogenetics, pharmacoepigenetics and clinical significance.

CONCLUSION

Knowledge about the substrates, inducers, and inhibitors of CYP isoforms, as well as the polymorphisms of CYP enzymes may be used as an aid by clinicians to determine therapeutic strategy, and treatment doses for drugs that are metabolized by CYP gene products.

Gedunin, A Neem Limonoid in Combination with Epalrestat Inhibits Cancer Hallmarks by Attenuating Aldose Reductase-Driven Oncogenic Signaling in SCC131 Oral Cancer Cells

Methods:

The expression of AR and key molecules involved in cell proliferation, apoptosis, autophagy, invasion and angiogenesis was analysed by qRT-PCR, and immunoblotting. ROS generation and cell cycle were analysed by FACS. Alamar blue assay and scratch assay were used to evaluate cell proliferation and migration in the endothelial cell line Eahy926.

Results:

Gedunin and the AR inhibitor epalrestat inhibited AR expression and ROS generation. Cell cycle arrest at G1/S was associated with cell death by autophagy with subsequent switch over to apoptosis. Furthermore, hypoxia-induced cell migration was inhibited in Eahy926 cells with downregulation of pro-invasive and proangiogenic proteins in SCC131 as well as Eahy926 cells. Co-inactivation of Akt and ERK was coupled with abrogation of IKK/NF-κB signaling. However, the combination of gedunin and epalrestat was more effective than single agents.

Conclusion:

Inhibition of AR-mediated ROS signalling may be a key mechanism by which gedunin and epalrestat exert their anticancer effects. Our results provide compelling evidence that the combination of gedunin and epalrestat modulates expression of key oncogenic signalling kinases and transcription factors primarily by influencing phosphorylation and subcellular localisation. AR inhibitors such as gedunin and epalrestat are novel candidate agents for cancer prevention and therapy.

Impact of stainless-steel welding fumes on proteins and non-coding RNAs regulating DNA damage response in the respiratory tract of Sprague-Dawley rats

Substantial evidence has established the negative impact of inhalation exposure to welding fumes on respiratory functions. The aim of the present study was to investigate the effect of welding fume inhalation on expression of molecules that function as sensors, transducers and effectors of DNA damage response (DDR) in the respiratory tract of male Sprague-Dawley rats. Animals were exposed to 50 mg/m³ stainless steel welding fumes for 1 h/d for 4, 8, and 12 weeks, respectively. Histological examination demonstrated preneoplastic changes in trachea and bronchi with focal atelectasis and accumulation of chromium (Cr) in the lungs. This was associated with elevated levels of DNA damage markers (8-oxodG, γH2AX), ATM phosphorylation, cell cycle arrest, apoptosis induction, activation of homologous recombination (HR), non-homologous end joining (NHEJ), and Nrf2 signaling, as well as altered expression of noncoding RNAs (ncRNAs). However, after 12 weeks of exposure, DDR was compromised as reflected by resumption of the cell cycle, repair inhibition, and failure of apoptosis. Data demonstrate that exposure to welding fumes influences two crucial layers of DDR regulation, phosphorylation of key proteins in NHEJ and HR, as well as the ncRNAs that epigenetically modulate DDR. Evidence indicates that marked DNA damage coupled with non-productive DNA repair and apoptosis avoidance may be involved in neoplastic transformation.

Nimbolide, a neem limonoid inhibits cytoprotective autophagy to activate apoptosis via modulation of the PI3K/Akt/GSK-3β signalling pathway in oral cancer

Of late, nimbolide, a limonoid from the neem tree (Azadirachta indica) has gained increasing research attention owing to its potent antiproliferative and apoptosis-inducing effects. The present study was designed to investigate the effect of nimbolide on autophagy and the time point at which the phosphorylation status of GSK-3β and PI3K dictate the choice between autophagy and apoptosis in SCC131 and SCC4 oral cancer cells. Additionally, we analysed changes in the expression of proteins involved in autophagy and apoptosis after therapeutic intervention with nimbolide in a hamster model of oral oncogenesis. Furthermore, we also demonstrate changes in the expression of key genes involved in apoptosis and autophagy during the stepwise evolution of hamster and human OSCCs. Nimbolide-induced stereotypical changes in oral cancer cells characteristic of both apoptosis and autophagy. Time-course experiments revealed that nimbolide induces autophagy as an early event and then switches over to apoptosis. Nimbolide negatively regulates PI3K/Akt signalling with consequent increase in p-GSK-3βTyr216, the active form of GSK-3β that inhibits autophagy. Downregulation of HOTAIR, a competing endogenous RNA that sponges miR-126 may be a major contributor to the inactivation of PI3K/Akt/GSK3 signalling by nimbolide. Analysis of key markers of apoptosis and autophagy as well as p-AktSer473 during sequential progression of hamster and human OSCC revealed a gradual evolution to a pro-autophagic and antiapoptotic phenotype that could confer a survival advantage to tumors. In summary, the results of the present study provide insights into the molecular mechanisms by which nimbolide augments apoptosis by overcoming the shielding effects of cytoprotective autophagy through modulation of the phosphorylation status of Akt and GSK-3β as well as the ncRNAs miR-126 and HOTAIR. Development of phytochemicals such as nimbolide that target the complex interaction between proteins and ncRNAs that regulate the autophagy/apoptosis flux is of paramount importance in cancer prevention and therapeutics.

Crosstalk between Raf-MEK-ERK and PI3K-Akt-GSK3β signaling networks promotes chemoresistance, invasion/migration and stemness via expression of CD44 variants (v4 and v6) in oral cancer

BACKGROUND

The cell-surface glycoprotein CD44 is an important oral cancer stem cell (OCSC) marker and plays significant role in oral squamous cell carcinoma (OSCC) aggressiveness, however, the regulation of CD44 is incompletely understood.

METHODS

In the present study, 145 fresh human OSCC tissue specimens, including 18 adjacent normal, 42 noninvasive (N0), 53 invasive tumor samples (N_1-3) and 32 chemo-radiation resistant samples (RCRT), were included. The expression of CD44 standard (CD44s) and variants (CD44v4, CD44v6); the activation of pERK1/2, GSK3β, NICD (Notch) pathways; the cell viability; and the MMP-9/-2 activity were assessed using RT-PCR, immunohistochemistry, Western blotting, MTT assay and gelatin zymography. OSCC cell lines, including parental (SCC9/SCC4) and Cisplatin-resistant (CisR-SCC9/-SCC4) cells, were used. Knock down of CD44v4/CD44v6 (by siRNA) or inactivation of MAPK/PI3K pathways using specific PD98059/LY294002 was achieved for in vitro analysis of chemoresistance and invasion/migration.

RESULTS

Elevated CD44 variants were associated with overall OSCC progression, chemoresistance and invasion. Positive correlations were observed, mainly between the expression of CD44v4 and the activation of ERK1/2 causing chemoresistance, whereas CD44v6 expression and inactivation of GSK3β caused invasiveness of OSCC. Cisplatin resistant, CisR-SCC9/SCC4 cell lines showed OCSC properties. Inhibition of MEK/ERK1/2 by SMI or knock down (KD) of CD44v4 by siRNA reversed cisplatin-resistance, whereas blocking the PI3K/Akt/GSK3β pathway by SMI or KD of CD44v6 isoforms by respective siRNA diminished invasion/metastasis potential.

CONCLUSION

Collectively, our results demonstrated that CD44v4 expression is more linked with ERK1/2 activation and promote cisplatin resistance, whereas CD44v6 expression is associated primarily with PI3K/Akt/GSK3β activation and driving tumor invasion/migration.

Glycogen synthase kinase-3β mediated regulation of matrix metalloproteinase-9 and its involvement in oral squamous cell carcinoma progression and invasion

PURPOSE

Oral squamous cell carcinoma (OSCC)-related deaths mainly result from invasion of the tumor cells into local cervical lymph nodes. It has been reported that progressive basement membrane loss promotes the metastatic and invasive capacities of OSCCs. Matrix metalloproteinase-9 (MMP-9) is known to play a central role in tumor progression and invasion. However, the role of MMP-9 in OSCC invasion has so far remained paradoxical and little is known about its regulation. Here, we aimed to assess MMP-9 expression regulation and its activation by glycogen synthase kinase-3β during human OSCC progression and invasion.

METHODS

In the present study, 178 human OSCC samples, including 118 fresh samples (18 adjacent normal, 42 noninvasive and 58 invasive tumor samples) and 60 archival human tissue microarray (TMA) tongue cancer samples, were included. mRNA expression, protein expression, MMP-9/-2 activity, protein-protein interaction and Snail, c-Myc, β-catenin and TIMP1 expression were assessed using RT-PCR, immunohistochemistry, Western blotting, co-immunoprecipitation and gelatin zymography analyses, respectively. Wnt5a and LPA mediated MMP-9 regulation was assessed in OCSCC-derived SCC-9 cells exogenously expressing GSK3β (WT) or non phosphoryable GSK3β (S9A).

RESULTS

We observed a progressive up-regulation/activation of MMP-9 at various stages of oral tumor progression/invasion. Positive correlations were observed between MMP-9 and c-Myc expression, MMP-9 and MMP-2 activity, MMP-9 and TIMP1 expression and MMP-9 activity and TIMP1-MMP-9 interaction. In contrast, a negative correlation between phosphorylated β-catenin and MMP-9 expression was observed. Conversely, we found that in oral tongue SCC MMP-9 expression was positively correlated with inactivation of GSK3 signaling. Finally, we found that Wnt5a and LPA mediated increased MMP-9 and decreased GSK3β activities in tongue SCC-derived SCC-9 cells. MMP-9 regulation by GSK3β was confirmed by using phosphoryable/regulatory GSK3β (WT construct) and not by non-phosphoryable GSK3β (S9A construct).

CONCLUSIONS

Collectively, our results show that MMP-9 overexpression and activation are important events occurring during OSCC progression/invasion and that this overexpression/activation is regulated by c-Myc, active MMP-2 and inactive GSK3β mediated pathways.

Expression of β1integrin in normal epithelium, oral submucous fibrosis and oral squamous cell carcinoma

INTRODUCTION AND AIMS

The possible reason suggested for epithelial atrophy in oral submucous fibrosis (OSMF) is ischemia. Dysregulation in the epithelial proliferation and maturation is also thought to be a cause. The β1 integrin identifies the oral epithelial stem cells. The changes induced by the arecanut on these cells may result in epithelial alterations. The aim of this study is to evaluate the stem cells distribution and percentage by assessing the β1 integrin expression.

MATERIALS AND METHODS

The study included normal oral mucosa (15 cases) and disease group (97 cases). The disease group was further subdivided into early (29 cases), moderate (34 cases), advanced OSMF (18 cases) and oral squamous cell carcinoma(OSCC) associated with OSMF (16 cases). The tissues were stained for β1 integrin antibodies. The positive cells and staining intensities were analysed to determine the staining index, and statistically evaluated using KW test statistics.

RESULTS

β1 integrin was observed in retepegs region and the percentage of positive cells was 14%- 30% in the control. In OSMF, the β1 integrin positivity was observed in basal and suprabasal layers, and the percentage was ranged from 2%-71%. β1 integrin expression in OSCC was observed both in central and peripheral cells and ranged from 17%-85%. On comparison, the difference in staining index among normal, OSMF and carcinomas was significant at p<0.01. The stem cells percentage was increased both in OSMF and carcinomas. The non-dysplastic epithelium of OSMF with severe atrophy showed lowest percentage. It is inferred that absence of stem cells and proliferation may attribute for the atrophy.

Breast Cancer: Current Molecular Therapeutic Targets and New Players

Breast cancer is the most common cancer and the most frequent cause of cancer death among women worldwide. Breast cancer is a complex, heterogeneous disease classified into hormone-receptor-positive, human epidermal growth factor receptor-2 overexpressing (HER2+) and triple-negative breast cancer (TNBC) based on histological features. Endocrine therapy, the mainstay of treatment for hormone-responsive breast cancer involves use of selective estrogen receptor modulators (SERMs), selective estrogen receptor downregulators (SERDs) and aromatase inhibitors (AIs). Agents that target estrogen receptor (ER) and HER2 such as tamoxifen and trastuzumab have been the most extensively used therapeutics for breast cancer. Crosstalk between ER and other signalling networks as well as epigenetic mechanisms have been envisaged to contribute to endocrine therapy resistance. TNBC, a complex, heterogeneous, aggressive form of breast cancer in which the cells do not express ER, progesterone receptor or HER2 is refractory to therapy. Several molecular targets are being explored to target TNBC including androgen receptor, epidermal growth factor receptor (EGFR), poly(ADP-ribose) polymerase (PARP), and vascular endothelial growth factor (VEGF). Receptors, protein tyrosine kinases, phosphatases, proteases, PI3K/Akt signalling pathway, microRNAs (miRs) and long noncoding RNAs (lncRNAs) are potential therapeutic targets. miR-based therapeutic approaches include inhibition of oncomiRs by antisense oligonucleotides, restoration of tumour suppressors using miR mimics, and chemical modification of miRs. The lnRNAs HOTAIR, SPRY4-IT1, GAS5, and PANDAR, new players in tumour development and prognosis may have theranostic applications in breast cancer. Several novel classes of mechanism-based drugs have been designed and synthesised for treatment of breast cancer. Integration of nucleic acid sequencing studies with mass spectrometry-based peptide sequencing and posttranslational modifications as well as rational drug design will provide a more comprehensive understanding of the pathophysiology of breast cancer and help in evolving therapeutic strategies.

Nimbolide upregulates RECK by targeting miR-21 and HIF-1α in cell lines and in a hamster oral carcinogenesis model

Reversion-inducing cysteine-rich protein with Kazal motifs (RECK), a potent inhibitor of matrix metalloproteinases (MMPs) is a common negative target of oncogenic signals and a potential therapeutic target for novel drug development. Here, we show that sequential RECKlessness stimulates angiogenesis and Notch signalling in the 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis model, a paradigm for oral oncogenesis and chemointervention. We also report the chemotherapeutic effect of nimbolide, a limonoid from the neem tree (Azadirachta indica) based on the upregulation of RECK as well as modulation of the expression of key molecules involved in invasion and angiogenesis. We demonstrate that nimbolide upregulates RECK by targeting miR-21, and HIF-1α resulting in reduced MMP activity and blockade of VEGF and Notch signalling. Nimbolide reduced microvascular density, confirming its anti-angiogenic potential. Molecular docking analysis revealed interaction of nimbolide with HIF-1α. Additionally, we demonstrate that nimbolide upregulates RECK expression via downregulation of HIF-1α and miR-21 by overexpression and knockdown experiments in SCC4 and EAhy926 cell lines. Taken together, these findings provide compelling evidence that targeting RECK, a keystone protein that regulates mediators of invasion and angiogenesis with phytochemicals such as nimbolide may be a robust therapeutic approach to prevent oral cancer progression.

The elevated activation of NFκB and AP-1 is correlated with differential regulation of Bcl-2 and associated with oral squamous cell carcinoma progression and resistance

OBJECTIVES

Oral cancer is the sixth most common cancer in the world. Failure of chemoradiation therapy is a major concern for treating oral cancer patients. The objective of this study is to determine the B cell lymphoma-2 (bcl-2) expression and its regulation by nuclear factor κB (NFκB) and activator protein 1 (AP-1) in oral cancer progression and chemoradiation resistance.

MATERIALS AND METHODS

In the present study, a total of 123 (n = 123) human samples were included. Briefly, 64 fresh samples were from adjacent normal (AN), primary oral tumors without treatment (PT), and tumors with resistance to chemoradiation therapy with local recurrence (RCRT). Fifty-nine samples were human tongue cancers and normal samples (TMA). Messenger RNA (mRNA) expression levels of bcl-2 and protein levels of bcl-2, NFκB, AP-1, and inactive GSK3α/β were measured by semiquantitative RT-PCR, immunohistochemistry, Western blot, and ChIP analysis.

RESULTS

Increased bcl-2 expression was observed in PT compared to AN. The RCRT tumors showed maximum expression of bcl-2 mRNA and protein over the PT and AN groups. Bcl-2 protein and mRNA expression were positively correlated with NFκB and AP-1 expression. AP-1 expression was strongly correlated with bcl-2 in the RCRT group of tumors. Further, inactive GSK3α/β showed a positive trend with bcl-2 expression in oral tongue cancer specimens.

CONCLUSION

Collectively, our results demonstrated cumulative effect of AP-1 and NFĸB for bcl-2 gene regulation in overall PT progression and chemoradiation resistance. The study provides evidence of increased bcl-2 mRNA/protein fueled by NFĸB in PT and AP-1 in RCRT. These regulations of bcl-2 by NFκB and AP-1 are important in OSCC progression and chemoradiation resistance.

Reversion-inducing cysteine-rich protein with Kazal motifs and its regulation by glycogen synthase kinase 3 signaling in oral cancer

The reversion-inducing cysteine-rich protein with Kazal motifs (RECK) and glycogen synthase kinase (GSK3) are novel tumor suppressors, and emerging evidence has suggested their active role in oral cancer pathogenesis. In the present study, 112 human samples, including 55 fresh samples of 14 adjacent normal tissues, 25 noninvasive oral tumors, and 18 invasive tumors, were included. The messenger RNA (mRNA) expression, protein expression, and promoter methylation of the RECK gene, as well as the expression of GSK3β, phospho/total β-catenin, and c-myc, were measured by RT-PCR, bisulphate modification-PCR, immunohistochemistry, and Western blot analysis. Additionally, ectopic expression of in/active GSK3β was performed in cell culture experiments. This study provided information on the progressive silencing of RECK gene expression at the protein and mRNA levels paralleled with promoter hypermethylation at various stages of oral tumor invasion. RECK expression and the hypermethylation of the RECK gene promoter were negatively and positively correlated with pS⁹GSK3β/c-myc expression, respectively. Further, a negative trend of RECK protein expression with nuclear β-catenin expression was observed. Induced expression of active GSK3β reversed the RECK silencing in SCC9 cells. Collectively, our results demonstrated that the silencing of the RECK gene, possibly regulated by the GSK3β pathway, is an important event in oral cancer invasion and this pathway could be exploited for therapeutic interventions.

Nimbolide, a neem limonoid inhibits Phosphatidyl Inositol-3 Kinase to activate Glycogen Synthase Kinase-3β in a hamster model of oral oncogenesis

Glycogen synthase kinase-3β (GSK-3β), a serine/threonine kinase is frequently inactivated by the oncogenic signalling kinases PI3K/Akt and MAPK/ERK in diverse malignancies. The present study was designed to investigate GSK-3β signalling circuits in the 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis model and the therapeutic potential of the neem limonoid nimbolide. Inactivation of GSK-3β by phosphorylation at serine 9 and activation of PI3K/Akt, MAPK/ERK and β-catenin was associated with increased cell proliferation and apoptosis evasion during stepwise evolution of HBP carcinomas. Administration of nimbolide inhibited PI3K/Akt signalling with consequent activation of GSK-3β thereby inducing trafficking of β-catenin away from the nucleus and enhancing the expression of miR-126 and let-7. Molecular docking studies confirmed interaction of nimbolide with PI3K, Akt, ERK and GSK-3β. Furthermore, nimbolide attenuated cell proliferation and induced apoptosis as evidenced by increased p-cyclin D1^Thr286 and pro-apoptotic proteins. The present study has unravelled aberrant phosphorylation as a key determinant for oncogenic signalling and acquisition of cancer hallmarks in the HBP model. The study has also provided mechanistic insights into the chemotherapeutic potential of nimbolide that may be a useful addition to the armamentarium of natural compounds targeting PI3K for oral cancer treatment.

The Hamster Buccal Pouch Model of Oral Carcinogenesis

The hamster buccal pouch (HBP) carcinogenesis model is one of the most well-characterized animal tumor models used as a prelude to investigate multistage oral carcinogenesis and to assess the efficacy of chemointervention. Hamster buccal pouch carcinomas induced by 7,12-dimethylbenz[a]anthracene (DMBA) show extensive similarities to human oral squamous cell carcinomas. The HBP model offers a number of advantages including a simple and predictable tumor induction procedure, easy accessibility for examination and follow-up of lesions, and reproducibility. This model can be used to test both chemopreventive and chemotherapeutic agents.

Gedunin abrogates aldose reductase, PI3K/Akt/mToR, and NF-κB signaling pathways to inhibit angiogenesis in a hamster model of oral carcinogenesis

Aberrant activation of oncogenic signaling pathways plays a central role in tumor development and progression. The aim of this present study was to investigate the chemopreventive effects of the neem limonoid gedunin in the hamster model of oral cancer based on its ability to modulate aldose reductase (AR), phosphatidyl inositol-3-kinase (PI3K)/Akt, and nuclear factor kappa B (NF-κB) pathways to block angiogenesis. Administration of gedunin suppressed the development of HBP carcinomas by inhibiting PI3K/Akt and NF-κB pathways through the inactivation of Akt and inhibitory kappa B kinase (IKK), respectively. Immunoblot and molecular docking interactions revealed that inhibition of these signaling pathways may be mediated via inactivation of AR by gedunin. Gedunin blocked angiogenesis by downregulating the expression of miR-21 and the pro-angiogenic factors vascular endothelial growth factor and hypoxia inducible factor-1 alpha (HIF-1α). In conclusion, the results of the present study provide compelling evidence that gedunin prevents progression of hamster buccal pouch (HBP) carcinomas via inhibition of the kinases Akt, IKK, and AR, and the oncogenic transcription factors NF-κB and HIF-1α to block angiogenesis.

Ellagic acid inhibits VEGF/VEGFR2, PI3K/Akt and MAPK signaling cascades in the hamster cheek pouch carcinogenesis model

BACKGROUND

Blocking vascular endothelial growth factor (VEGF) mediated tumor angiogenesis by phytochemicals has emerged as an attractive strategy for cancer prevention and therapy.

METHODS

We investigated the anti-angiogenic effects of ellagic acid in a hamster model of oral oncogenesis by examining the transcript and protein expression of hypoxia-inducible factor-1alpha (HIF-1α), VEGF, VEGFR2, and the members of the PI3K/Akt and MAPK signaling cascades. Molecular docking studies and cell culture experiments with the endothelial cell line ECV304 were performed to delineate the mechanism by which ellagic acid regulates VEGF signaling.

RESULTS

We found that ellagic acid significantly inhibits HIF-1α-induced VEGF/VEGFR2 signalling in the hamster buccal pouch by abrogating PI3K/Akt and MAPK signaling via downregulation of PI3K, PDK-1, p-Akt(ser473), mTOR, p-ERK, and p-JNK. Ellagic acid was also found to reduce the expression of histone deacetylases that could inhibit neovascularization. Analysis of the mechanism revealed that ellagic acid inhibits hypoxia-induced angiogenesis via suppression of HDAC-6 in ECV304 cells. Furthermore, knockdown of endogenous HDAC6 via small interfering RNA abrogated hypoxia-induced expression of HIF-1α and VEGF and blocked Akt activation. Molecular docking studies confirmed interaction of ellagic acid with upstream kinases that regulate angiogenic signaling.

CONCLUSIONS

Taken together, these findings demonstrate that the anti-angiogenic activity of ellagic acid may be mediated by abrogation of hypoxia driven PI3K/Akt/mTOR, MAPK and VEGF/VEGFR2 signaling pathways involving suppression of HDAC6 and HIF-1α responses.

GENERAL SIGNIFICANCE

Ellagic acid offers promise as a lead compound for anticancer therapeutics by virtue of its ability to inhibit key oncogenic signaling cascades and HDACs.

Chemopreventive potential of chlorophyllin: a review of the mechanisms of action and molecular targets

Chlorophyllin (CHL), a water soluble semisynthetic derivative of the ubiquitous plant pigment chlorophyll used as a food additive, is recognized to confer a wide range of health benefits. CHL has been shown to exhibit potent antigenotoxic, anti-oxidant, and anticancer effects. Numerous experimental and epidemiological studies have demonstrated that dietary supple-mentation of CHL lowers the risk of cancer. CHL inhibits cancer initiation and progression by targeting multiple molecules and pathways involved in the metabolism of carcinogens, cell cycle progression, apoptosis evasion, invasion, and angiogenesis. The modulatory effects of CHL on the hallmark capabilities of cancer appear to be mediated via abrogation of key oncogenic signal transduction pathways such as nuclear factor kappa B, Wnt/β-catenin, and phosphatidylinositol-3-kinase/Akt signaling. This review provides insights into the molecular mechanisms of the anticancer effects of dietary CHL.

Expression and inactivation of glycogen synthase kinase 3 alpha/ beta and their association with the expression of cyclin D1 and p53 in oral squamous cell carcinoma progression

Background

The study aims to evaluate the expression and activity of glycogen synthase kinase 3 isoforms α/β (GSK3α/β) and to assess their oncogenic potential through a correlation with the expression of cyclin D1 and p53 in oral cancer.

Methods

The expression of total and phosphorylated GSK3α/β as well as cyclin D1 and p53 together with their interaction were assessed in human oral cancer tissue samples, apparently normal adjacent tissues, benign tumor samples, premalignant lesions and healthy normal tissues (total 179) using various methods, such as immunohistochemistry, Western blot assays, immunoprecipitation and RT-PCR analysis.

Results

The expression of GSK3β was significantly higher relative to GSK3α indicating the greater role of the β isoform in oral cancer. Among various types of oral cancers, OSCC (of the lip and tongue) showed elevated expression of GSK3α/β, and the expression was correlated with disease progression. The increased expression of pS²¹GSK3α and pS⁹GSK3β not only correlated positively with cyclin D1 and p53 expression in tongue cancer progression but a gradual shift of their expression from the cytoplasmic to the nuclear compartment and overall disease severity was also observed. The interaction of GSK3β-cyclin D1 and the positive correlation of pS⁹GSK3β and the transcription of cyclin D1 were observed.

Conclusions

These results demonstrate that the inactivation of GSK3β is an important event in OSCC and can be used as a marker for assessing disease severity and may be exploited for therapeutic intervention.

Astaxanthin inhibits JAK/STAT-3 signaling to abrogate cell proliferation, invasion and angiogenesis in a hamster model of oral cancer

Identifying agents that inhibit STAT-3, a cytosolic transcription factor involved in the activation of various genes implicated in tumour progression is a promising strategy for cancer chemoprevention. In the present study, we investigated the effect of dietary astaxanthin on JAK-2/STAT-3 signaling in the 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis model by examining the mRNA and protein expression of JAK/STAT-3 and its target genes. Quantitative RT-PCR, immunoblotting and immunohistochemical analyses revealed that astaxanthin supplementation inhibits key events in JAK/STAT signaling especially STAT-3 phosphorylation and subsequent nuclear translocation of STAT-3. Furthermore, astaxanthin downregulated the expression of STAT-3 target genes involved in cell proliferation, invasion and angiogenesis, and reduced microvascular density, thereby preventing tumour progression. Molecular docking analysis confirmed inhibitory effects of astaxanthin on STAT signaling and angiogenesis. Cell culture experiments with the endothelial cell line ECV304 substantiated the role of astaxanthin in suppressing angiogenesis. Taken together, our data provide substantial evidence that dietary astaxanthin prevents the development and progression of HBP carcinomas through the inhibition of JAK-2/STAT-3 signaling and its downstream events. Thus, astaxanthin that functions as a potent inhibitor of tumour development and progression by targeting JAK/STAT signaling may be an ideal candidate for cancer chemoprevention.

Cytomodulin-1, a synthetic peptide abrogates oncogenic signaling pathways to impede invasion and angiogenesis in the hamster cheek pouch carcinogenesis model

Constitutive activation of the various oncogenic signaling pathways plays a pivotal role in promoting malignant transformation. The aim of this study was to investigate the therapeutic potential of a synthetic bioactive heptapeptide cytomodulin-1 (CM-1) against hamster cheek pouch carcinomas based on its influence on the predominant carcinogenic signaling pathways - NF-κB, TGFβ, and Wnt/β-catenin and their downstream target events invasion and angiogenesis. Topical application of CM-1 to DMBA-painted hamsters significantly inhibited activation of the canonical NF-κB pathway by blocking kinase activity of IKKβ and increasing the cytosolic accumulation of the inhibitor IκB-α. In addition, CM-1 inactivated IKKβ by disrupting IKKβ/Nemo interactions. CM-1 also hampered the activation of TGFβ and Wnt/β-catenin signaling by averting the phosphorylation of the key upstream ser/thr kinases TGFβ RI and GSK-3β respectively. Attenuation of these oncogenic signaling pathways by CM-1 also mitigated invasion and angiogenesis by suppressing the expression of pro-invasive matrix metalloproteinases, pro-angiogenic VEGF and HIF-1α and upregulating the anti-angiogenic TIMP-2. Synthetic peptides such as CM-1 that target multiple key molecules in oncogenic signaling pathways and their downstream events are ideal candidate agents for cancer chemotherapy.

Neem Limonoids as Anticancer Agents: Modulation of Cancer Hallmarks and Oncogenic Signaling

Neem (Azadirachta indica A. Juss) is one of the most versatile medicinal plants, widely distributed in the Indian subcontinent. Neem is a rich source of limonoids that are endowed with potent medicinal properties predominantly antioxidant, anti-inflammatory, and anticancer activities. Azadirachtin, gedunin, and nimbolide are more extensively investigated relative to other neem limonoids. Accumulating evidence indicates that the anticancer effects of neem limonoids are mediated through the inhibition of hallmark capabilities of cancer such as cell proliferation, apoptosis evasion, inflammation, invasion, and angiogenesis. The neem limonoids have been demonstrated to target oncogenic signaling kinases and transcription factors chiefly, NF-κB, Wnt/β-catenin, PI3K/Akt, MAPK, and JAK/STAT signaling pathways. Neem limonoids that target multiple pathways that are aberrant in cancer are ideal candidates for cancer chemoprevention and therapy.

Astaxanthin inhibits NF-κB and Wnt/β-catenin signaling pathways via inactivation of Erk/MAPK and PI3K/Akt to induce intrinsic apoptosis in a hamster model of oral cancer

BACKGROUND

The oncogenic transcription factors NF-κB and β-catenin, constitutively activated by upstream serine/threonine kinases control several cellular processes implicated in malignant transformation including apoptosis evasion. The aim of this study was to investigate the chemopreventive effects of astaxanthin, an antioxidant carotenoid, in the hamster buccal pouch (HBP) carcinogenesis model based on its ability to modulate NF-κB and Wnt signaling pathways and induce apoptosis.

METHODS

We determined the effect of dietary supplementation of astaxanthin on the oncogenic signaling pathways - NF-κB and Wnt/β-catenin, their upstream activator kinases - Erk/MAPK and PI-3K/Akt, and the downstream event - apoptosis evasion by real-time quantitative RT-PCR, western blot, and immunohistochemical analyses.

RESULTS

We found that astaxanthin inhibits NF-κB and Wnt signaling by downregulating the key regulatory enzymes IKKβ and GSK-3β. Analysis of gene expression and docking interactions revealed that inhibition of these pathways may be mediated via inactivation of the upstream signaling kinases Erk/Akt by astaxanthin. Astaxanthin also induced caspase-mediated mitochondrial apoptosis by downregulating the expression of antiapoptotic Bcl-2, p-Bad, and survivin and upregulating proapoptotic Bax and Bad, accompanied by efflux of Smac/Diablo and cytochrome-c into the cytosol, and induced cleavage of poly (ADP-ribose) polymerase (PARP).

CONCLUSIONS

The results provide compelling evidence that astaxanthin exerts chemopreventive effects by concurrently inhibiting phosphorylation of transcription factors and signaling kinases and inducing intrinsic apoptosis.

GENERAL SIGNIFICANCE

Astaxanthin targets key molecules in oncogenic signaling pathways and induces apoptosis and is a promising candidate agent for cancer prevention and therapy.

Chemopreventive effects of diverse dietary phytochemicals against DMBA-induced hamster buccal pouch carcinogenesis via the induction of Nrf2-mediated cytoprotective antioxidant, detoxification, and DNA repair enzymes

Identifying agents that activate nuclear factor erythroid-2 related factor-2 (Nrf2), a key regulator of various cytoprotective antioxidant, and detoxifying enzymes has evolved as a promising strategy for cancer chemoprevention. In the present study, we investigated the effect of dietary supplementation of structurally diverse phytochemicals- astaxanthin, blueberry, chlorophyllin, ellagic acid, and theaphenon-E on Nrf2 signaling, and xenobiotic-metabolizing and antioxidant enzymes in the 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis model. We observed that these phytochemicals induce nuclear accumulation of Nrf2 while downregulating its negative regulator, Keap-1. This was associated with reduced expression of CYP1A1 and CYP1B1, the cytochrome P450 isoforms involved in the activation of DMBA, and the oxidative stress marker 8-hydroxy-2'-deoxyguanosine coupled with upregulation of the phase II detoxification enzymes glutathione S-transferases and NAD(P)H:quinone oxidoreductase 1 and the antioxidant enzymes superoxide dismutase, catalase, and glutathione peroxidase. In addition, these dietary phytochemicals also enhanced the DNA repair enzymes 8-oxoguanine glycosylase 1 (OGG1), xeroderma pigmentosum D (XPD), xeroderma pigmentosum G (XPG), and x-ray repair cross complementing group 1 (XRCC1). Our data provide substantial evidence that the dietary phytochemicals inhibit the development of HBP carcinomas through the activation of Nrf2/Keap-1 signaling and by upregulating cytoprotective enzymes. The extent of the chemopreventive effects of the phytochemicals was in the order: chlorophyllin > blueberry > ellagic acid > astaxanthin > theaphenon-E. Thus these dietary phytochemicals that function as potent activators of Nrf2 and its orchestrated response are novel candidates for cancer chemoprevention.

The importance of oncogenic transcription factors for oral cancer pathogenesis and treatment

Oral squamous cell carcinoma is a major cause of morbidity and mortality worldwide. Current experimental evidence shows that most important risk factors for oral cancer include tobacco use and excessive alcohol consumption and less well-defined risks include viral infection and a diet deficient in antioxidants. The positive correlation between various risk/etiologic factors of oral cancer and the activation of various transcription factors (TFs) has been reported in the literature. Although initially, TFs were considered to be very difficult targets for use in clinical treatment, recent technological advances have provided the ability to control these factors of cancer progression. This review focuses on the role of oncogenic transcription factors in oral cancer, their modes of activation through various biological pathways, the promises and pitfalls in viewing them as potent oncotargets, the way they can be controlled based on the current understanding, and the future research to be done in this area.

RECKing MMP: relevance of reversion-inducing cysteine-rich protein with kazal motifs as a prognostic marker and therapeutic target for cancer (a review)

Reversion-inducing-cysteine-rich protein with Kazal motifs (RECK) is a membrane-anchored glycoprotein that negatively regulates the activities of matrix metalloproteinases (MMPs) and inhibits tumor invasion, metastasis, and angiogenesis. RECK is essential for normal development and is a key mediator of tissue remodeling and stabilization of tissue architechture. Downregulation of RECK documented in a wide range of malignant neoplasms correlates with poor prognosis, and tumor metastasis. The RECK gene is a common negative target for oncogenic signals that act on the Sp1-binding site of the RECK promoter. Both natural and synthetic agents have been identified as upregulators of RECK. Several strategies have been proposed to enhance RECK expression including forced expression of RECK, use of mimetics, recombinant peptides, microRNA antagonists, and gene therapy. Upregulation of RECK could be a valuable therapeutic option to improve prognosis and block tumor progression. This review addresses the potential value of RECK as a prognostic marker and as a molecular target for cancer therapy.

Chlorophyllin abrogates canonical Wnt/β-catenin signaling and angiogenesis to inhibit the development of DMBA-induced hamster cheek pouch carcinomas

BACKGROUND

Chlorophyllin, a water soluble semi-synthetic food-grade derivative is reported to exhibit a wide range of beneficial health effects. We investigated the effect of chlorophyllin supplementation on Wnt/β-catenin and vascular endothelial growth factor (VEGF) signaling in the 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis model.

METHODS AND RESULTS

Hamsters were divided into 4 groups. The right buccal pouches of group 1 and 2 hamsters were painted with 0.5 % DMBA for 14 weeks. Group 2 animals received in addition chlorophyllin (4 mg/kg bw) in the diet. Group 3 animals received chlorophyllin alone and group 4 animals served as control. mRNA and protein expression of components of Wnt, VEGF, and PI3K/Akt signaling pathways were analyzed by RT-PCR and Western blot analysis. Dietary chlorophyllin administration suppressed the development of HBP carcinomas by altering the expression of several components of the Wnt/β-catenin signaling pathway. This was associated with inhibition of angiogenesis as evidenced by decreased expression of the proangiogenic factors HIF-1α, VEGF, and VEGFR2. Chlorophyllin administration also downregulated the expression of histone deacetylases involved in epigenetic regulation of tumor angiogenesis.

CONCLUSION

Dietary chlorophyllin that abrogates Wnt/β-catenin and VEGF signaling by targeting a multitude of key signaling molecules is an attractive candidate for preventing tumor progression.

Investigation of the chemopreventive potential of neem leaf subfractions in the hamster buccal pouch model and phytochemical characterization

Chemoprevention by medicinal plants has evolved as a practical strategy to control the incidence of cancer. Azadirachta indica (neem) containing various bioactive components is a promising candidate for chemoprevention. The present study was undertaken to evaluate the chemopreventive efficacy of the bioactive subfractions ethyl acetate chloroform insoluble fraction (ECIF) and the methanol ethyl acetate insoluble fraction (MEIF) following activity-guided fractionation of neem leaf extract. Analysis of the mechanism of chemoprevention revealed multitargeted mode of action that involved modulation of xenobiotic-metabolizing enzymes, inhibition of cell proliferation, induction of mitochondrial apoptosis, and abrogation of NF-κB signaling. HP-TLC, GC-MS and LC-MS analyses indicated the presence of several polar phytochemical entities in the neem leaf subfractions that might be responsible for their potent chemopreventive efficacy.

Cytogenetic analyses of Azadirachtin reveal absence of genotoxicity but marked antiproliferative effects in human lymphocytes and CHO cells in vitro

In this work we have examined the genotoxic potential of the bioinsecticide Azadirachtin A (AZA) and its influence on cell proliferation on human lymphocytes and Chinese Hamster ovary (CHO) cells. AZA genotoxicity was assessed by the analysis of chromosomal aberrations and sister chromatid exchanges (SCEs) in the absence and presence of rat liver S9 metabolism. Primary DNA damage was also investigated by means of the comet assay. The results obtained clearly indicate that AZA is not genotoxic in mammalian cells. On the other hand, AZA proved to interfere with cell cycle progression as shown by modulation of frequencies of first (M1) and second division (M2) metaphases detected by 5-Bromo-2'-deoxyuridine labeling. Accumulation of M1 metaphases were more pronounced in human lymphocytes. In the transformed CHO cell line, however, significant increases of multinucleated interphases and polyploid cells were observed at long treatment time. At higher dose-levels, the incidence of polyploidy was close to 100%. Identification of spindle structure and number of centrosomes by fluorescent immunostaining with α- and γ-tubulin antibodies revealed aberrant mitoses exhibiting multipolar spindles with several centrosomal signals. These findings suggest that AZA can act either through a stabilizing activity of microtubules or by inhibition of Aurora A, since both mechanisms are able to generate genetically unstable polyploid cells with multipolar spindles and multinucleated interphases.

Carcinoma of the stomach: A review of epidemiology, pathogenesis, molecular genetics and chemoprevention

Carcinoma of the stomach is still the second most common cause of cancer death worldwide, although the incidence and mortality have fallen dramatically over the last 50 years in many regions. The incidence of gastric cancer varies in different parts of the world and among various ethnic groups. Despite advances in diagnosis and treatment, the 5-year survival rate of stomach cancer is only 20 per cent. Stomach cancer can be classified into intestinal and diffuse types based on epidemiological and clinicopathological features. The etiology of gastric cancer is multifactorial and includes both dietary and nondietary factors. The major diet-related risk factors implicated in stomach cancer development include high content of nitrates and high salt intake. Accumulating evidence has implicated the role of Helicobacter pylori (H. pylori) infection in the pathogenesis of gastric cancer. The development of gastric cancer is a complex, multistep process involving multiple genetic and epigenetic alterations of oncogenes, tumor suppressor genes, DNA repair genes, cell cycle regulators, and signaling molecules. A plausible program for gastric cancer prevention involves intake of a balanced diet containing fruits and vegetables, improved sanitation and hygiene, screening and treatment of H. pylori infection, and follow-up of precancerous lesions. The fact that diet plays an important role in the etiology of gastric cancer offers scope for nutritional chemoprevention. Animal models have been extensively used to analyze the stepwise evolution of gastric carcinogenesis and to test dietary chemopreventive agents. Development of multitargeted preventive and therapeutic strategies for gastric cancer is a major challenge for the future.