Abstract 3336: Comparison of epithelial mesenchymal transition mediated TKI resistanc NSCLC cells containing wild type EGFR and mutant EGFR

Epithelial to mesenchymal transition (EMT) is a vital process in development and of metastasis and occurs when epithelial cell lose their polarized structure, by reducing adherent junction proteins E-cadherin, Claudin and ZO-1 on the membrane. Cells with EMT are elongated spindle like structures due to upregulation of mesenchymal markers Vimentin and N-cadherin. EMT may be responsible for resistance to molecular targeted therapies such as tyrosine kinase inhibitors (TKIs) against EGFR which is used in patients with activated EGFR mutations. However, these patients acquire resistance to TKIs after prolonged use. This acquired resistance to TKIs may also be due to a secondary T790M mutation in the kinase domain which could be responsible for inducing EMT. EMT is regulated by p120-catenin which interacts with the Kaiso factor in the cell nucleus and inhibits the transcriptional repressor activity of Kaiso factor. Kaiso factor represses Wnt target genes such as ZEB-1. The binding of p120-catenin to Kaiso factor also increases Wnt signaling which results in loss of E-cadherin. Cells undergoing EMT can acquire cancer stem-cell like characteristics by expressing stem-cell marker ABCB1. Thus we investigated EMT characteristics in TKI-resistant NSCLC cells, H2170 ER (Erlotinib resistant), H358 ER and H1975. To determine modulation of EMT biomarkers in TKI-resistant cells, H1975 with L858R and T790M mutations was compared to TKI-sensitive cell line H3255 with L858R mutation, using immunoblotting, and qPCR. Expression of stem-cell markers ABCB1 and EMT biomarker E-cadherin are measured using flow cytometry. Key EMT-related proteins such as PRMT-1, Slug, Snail, Twist, p120-catenin, and Vimentin were upregulated by 3.2, 3.18, 6.2, 1.68, 4 and 6.5 fold, respectively, and E-cadherin, Claudin and ZO-1 were downregulated by 89%, 90% and 99% fold as compared to the H3255 TKI-sensitive cell line. We also observed upregulation of N-cadherin, ZEB-1 and Vimentin by 2.4, 2.6, and 12 fold and downregulation of E-cadherin by 50% in H1975 by qPCR. Immunofluorescence studies for Vimentin showed that H1975 cells were more elongated and stratified as compared to the H3255 that had polarized structures. 90% colocalization of p120-catenin and Kaiso factor was seen H1975 cells whereas 10% colocalization was seen in H3255 cells. Flow cytometry results indicated that there was significant increase in expression of stem cell marker ABCB1 in TKI resistant cells H2170 ER, H358 ER and H1975 in comparison to H2170 P(Parental), H358 P and H3255 TKI sensitive cells. In conclusion, our results indicate that EMT is mediated through PRMT-1, which methylates Twist, transcriptional repressor of E-cadherin along with Slug and Snail in H1975 cells with T790M mutation. Cancer stem-cell marker ABCB1 is specific for TKI resistant NSCLC cells which exhibit EMT.

Citation Format: Tsatsral Iderzorig, Sanjana Singh, Gagan Chhabra, Neelu Puri. Comparison of epithelial mesenchymal transition mediated TKI resistanc NSCLC cells containing wild type EGFR and mutant EGFR [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3336. doi:10.1158/1538-7445.AM2017-3336

Abstract 5263: Chemopreventive effects of dietary grapes on skin cancer

Non-melanoma skin cancer (NMSC) is the most commonly diagnosed malignancy in the United States, affecting more than 3 million Americans each year. Ultraviolet (UV) radiation from the sun, particularly its UVB component (290-320 nm), is an established causative factor for ~90% of skin cancers. The two most common forms of skin cancer, basal- and squamous- cell carcinomas, are treatable if detected early. However, they can be difficult to treat and potentially fatal if left until late stages. Further, epidemiological studies have suggested an amplified risk of other deadly cancers in individuals with a history of skin cancer. Therefore, it is important to design novel approaches, especially focusing on prevention, for the management of skin cancers. Studies from our laboratory and by others have shown that topical application of the grape antioxidant resveratrol possesses promise in the prevention of skin cancer. However, ideally cancer preventive agents need to be orally administrable for ease of use and broader human acceptability. With this in mind, in this study, we determined the efficacy of dietary grape powder (containing resveratrol in natural amalgamation with catechins, anthocyanins, polyphenols and flavonols) against UVB-mediated skin tumorigenesis in the SKH-1 hairless mouse model, which is regarded to have relevance to human NMSC. We employed a UVB initiation-promotion protocol in which the mice were subjected to chronic UVB exposure (180 mJ/cm2; twice weekly, for 28 weeks). The animals received either AIN-76A or grape powder (GP) fortified diet (3% and 5% GP, obtained from the California Table Grape Commission), all of which were sugar-matched to the highest GP content. Our data demonstrated that the consumption of GP at both 3% and 5% resulted in a significant inhibition in skin tumor incidence and delay in the onset of tumorigenesis. The average consumption of feed per mouse was 3.5 g/day, corresponding to 105 and 174 mg GP/day in the 3% and 5% GP treatment groups. This dosing regimen seems to be easily achievable for human consumption, as it corresponds to 25.5 and 42.4 g/day, which are equivalent to 1.1 and 1.8 serving of fresh grapes, respectively. Our data also demonstrated that the observed skin cancer chemopreventive effects of grape powder were accompanied by significant i) decreases in cellular proliferation markers Ki67 and PCNA, ii) decreases in the oxidative stress marker 4-HNE, and iii) increases in the levels of cleaved caspase 7 and poly (ADP-ribose) polymerase (PARP). Interestingly, NRF2, an activator of cellular antioxidant response, was found to be downregulated in GP treated tumors, compared to UVB alone groups, suggesting a potential protective role of NRF2 in the survival of tumor cells. Overall, our study suggests a strong chemopreventive effect of dietary grape and provides a basis for future human studies.

Citation Format: Chandra K. Singh, Mary A. Ndiaye, Charlotte A. Mintie, Gagan Chhabra, Nihal Ahmad. Chemopreventive effects of dietary grapes on skin cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5263. doi:10.1158/1538-7445.AM2017-5263

Abstract 4128: Mechanism of action of G-quadruplex forming oligonucleotide homologous to the telomere overhang in melanoma

T-oligo, a guanine-rich oligonucleotide (GRO) homologous to the 3'-telomeric overhang of telomeres, elicits potent DNA-damage responses (DDRs) in cancer cells. However, the detailed molecular mechanism of action of T-oligo in cancer cells is largely unknown. Recent studies suggest that GROs can form G-quadruplexes (G4) which are stabilized by the hydrogen-bonding of guanine residues. This study aims to examine the G4-forming capabilities of T-oligo in vitro and investigates the molecular mechanism of single-stranded (SS) and G4-T-oligo induced DDRs in melanoma cells (MM-AN). G4-formation by T-oligo was confirmed using the SS-T-oligo and G4-T-oligo on a polyacrylamide gel under non-denaturing conditions. NMR studies for T-oligo in KCl confirmed that T-oligo forms G4 structures. Immunofluorescence studies conducted with an anti-G-quadruplex antibody (BG4), a G4 detecting antibody, showed 88.4% co-localization of T-oligo and BG4 in the nuclei of melanoma cells confirming the ability of T-oligo to form G-quadruplexes inside melanoma cells. While G4-T-oligo was found more stable in nuclease degradation assay by DNase I, it had a decreased anti-proliferative effects compared to SS-T-oligo. However, G4-T-oligo had similar cellular uptake as SS-T-oligo. Further, two shelterin complex proteins TRF2 and POT1 which are mainly found at the telomere ends were found to be upregulated (2.0 fold) by T-oligo suggesting TRF2 and POT1 mediated telomere overhang dissociation. We also found that T-oligo can co-localize with telomere binding proteins TRF2 and POT1 by 88.4±4.5% (n=12) and 84.5±8% (n=10) respectively. Western blot analysis results also showed upregulation of both p-JNK and total JNK by 4.0- and 2.0-fold respectively. To further confirm the involvement of p-JNK in T-oligo mediated apoptosis we used a specific JNK inhibitor SP600125. Western blot analysis showed that T-oligo mediated upregulation of p-JNK was reversed in presence of SP600125. Results from an MTT assay showed a 73.8% decrease in cell viability after T-oligo treatment alone; however, cell viability was decreased to 45.8%, and 25.3% when SP600125 was present at concentrations of 10 μM, and 12 μM respectively, in comparison to diluent. T-oligo also inhibited mRNA expression of hTERT; a catalytic subunit of telomerase by 50% .We further investigated the effect of the JNK inhibitor SP600125 on hTERT expression and found that treatment with SP600125 in presence of T-oligo partially reversed the downregulation of hTERT. We found a 16% decrease in hTERT expression in comparison to 50% reduction by T-oligo treatment alone. In conclusion, these studies demonstrate that T-oligo can form G-quadruplexes and the anti-proliferative mechanism of T-oligo may be mediated through POT1 and TRF2 as well as via JNK-activation inducing hTERT-inhibition in melanoma cells.

Citation Format: Gagan Chhabra, Luke Wojdyla, Ankita Sanjali, Mark Frakes, Marko Ivancich, Pooja Vinay, Zachary Schrank, Benjamin E. Ramirez, Neelu Puri. Mechanism of action of G-quadruplex forming oligonucleotide homologous to the telomere overhang in melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4128. doi:10.1158/1538-7445.AM2017-4128

Melanoma Chemoprevention: Current Status and Future Prospects

The incidence of skin cancers, both nonmelanoma and melanoma, is increasing in the United States. The ultraviolet radiation, mainly from sun, is considered the major cause for these neoplasms. While nonmelanoma skin cancers are far more numerous, melanoma remains the most challenging. This is because melanoma can become extremely aggressive and its incidence is increasing worldwide due to lack of effective early detection, as well as disease recurrence, following both surgery and chemotherapy. Therefore, in addition to better treatment options, newer means are required to prevent melanomas from developing. Chemoprevention is a reasonable cost-effective approach to prevent carcinogenesis by inhibiting the processes of tumor initiation, promotion and progression. Melanoma is a progressive disease, which makes it very suitable for chemopreventive interventions, by targeting the processes and molecular pathways involved in the progression of melanoma. This review discusses the roles of various chemopreventive agents such as NSAIDs, statins, vitamins and dietary agents in melanoma and highlights current advancements and our perspective on future of melanoma chemoprevention. Although considerable preclinical data suggest that melanoma may be prevented or delayed by a numerous chemopreventive agents, we realize there are insufficient clinical studies evaluating their efficacy and long-term safety for human use.

Abstract LB-048: Investigating mechanism of action of oligonucleotides homologous to the telomere overhang in melanoma

Telomeres have become a popular target for novel cancer therapeutics because activation of telomerase is associated with development of immortality in nearly 90% of all cancers. It has been shown that administration of an oligonucleotide homologous to the telomere overhang called T-oligo (5’-GTTAGGGTTAG-3’) induces potent DNA damage responses (DDRs) in several cancers, including melanoma, and causes minimal toxicity to normal cells. Our study focuses on T-oligo which has the guanine rich character of the telomere 3’ overhang. The folding and stabilization of G-quadruplexes (G4) which are G-rich structures at the end of telomeres may be involved in regulation of telomere length and cell cycle regulation. To date, T-oligo has not been shown to form G4, although evidence suggests it has a G4-mediated mechanism of action. In this study, we investigate T-oligo's ability to form G4 structures in vitro. We hypothesize the additional secondary structure of G4 configured T oligo may confer increased stability, resistance to nucleases in serum and, initiate DDRs. G4 formation is a potential target since G4 presence can cause telomere uncapping leading to DDRs. In our studies, G4 T-oligo was formed by heating various concentrations of T-oligo in KCl solutions to 90°C and incubating at 60°C for 24-36 hours. G4 T-oligo formation was verified using native PAGE and NMR spectroscopy before subjecting it to DNase1 degradation and analyzing with native PAGE. We also analyzed the uptake and anti-proliferative ability of G4 T-oligo using FACS analysis and MTT assay respectively. The change in expression of TRF2 and JNK activity was performed using western blot analysis since T-oligo may induce activation of SAPK/JNK pathway. We further investigated the interaction between T-oligo and TRF2 using immunofluorescence (IF) with FITC labeled T-oligo in MM-AN melanoma cells. Densitometric analysis after nuclease digestion demonstrated a 52.6% decrease in T-oligo and a 20% decrease in G4 T-oligo as well as a 96% increase of single stranded T-oligo within the G4 T-oligo sample after 90 minutes, indicating nuclease resistance of G4-T-oligo. FACS analysis revealed G4 T-oligo and T-oligo had similar cellular uptake but G4 T-oligo was shown to be less effective in inhibiting cell proliferation suggesting the reduced anti-proliferative activity of G4 T-oligo is not likely attributed to cellular uptake. Western blot results showed upregulation of both p-JNK and total JNK by 4.0- and 2.0-fold respectively after 24 hour treatment. JNK has previously been demonstrated to be activated by G4 stabilizing ligands, providing more evidence that T-oligo may induce telomere dysfunction and upregulation of JNK activity. IF showed 80% co-localization of T-oligo and TRF2 in the nucleus suggesting T oligo may induce dissociation of TRF2 from the telomere shelterin complex causing DDRs. In conclusion, formation of G4 species by T-oligo may induce DDRs and future studies may provide insights into its mechanism of action and suggests new avenues for research.

Citation Format: Mark Frakes, Luke Wojdyla, Marko Ivancich, Perlina Fortinberry, Pooja Vinay, Priyanka Pandey, Gagan Chhabra, Neelu Puri. Investigating mechanism of action of oligonucleotides homologous to the telomere overhang in melanoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-048.

Abstract 1599: Epithelial mesenchymal transition and its role in TKI resistant NSCLC cell lines

NSCLC cells acquire resistance to EGFR and c-Met TKIs after prolonged use. Our studies indicate that resistance maybe due to upregulation of alternative signaling pathways such as Wnt and mTOR. We have found that activation of Wnt/β-Catenin is also associated with EMT which results in loss of cell adhesion properties and gain of motility and invasiveness. To understand the mechanism of TKI resistance in NSCLC cells with wild type EGFR, we have developed and used H2170-P (parental) cells and the TKI resistant H2170-ER (erlotinib resistant) and H2170-SR (SU11274 resistant) cells. We aim to study EMT and determine if inhibition of β-Catenin, a key regulator of transcription by siRNA or inhibition of ZEB-1 a transcriptional repressor of cell adhesion proteins by inducing mir-200a will help overcome the TKI resistance in NSCLC cells.

Using immunoblotting, we observed modulations in key EMT-related proteins in H2170-ER cells which showed upregulation of ZEB-1, N-cadherin, active beta-catenin, Vimentin, PRMT1 and ZO1 by 1.8, 2.4, 2, 1.8, 2.6 and 2 fold, respectively, and downregulation of E-cadherin (1.8 fold) as compared to H2170-P cells. Similar results were observed for H2170-SR cells. These results were verified using qPCR where we show that β-catenin (3.4-3.2 fold) and N-cadherin (2-1.9 fold) have increased gene expression while E-cadherin (1.7-2.4 fold) has a decreased gene expression in TKI resistant H2170-ER and SR cells when compared to H2170-P cells. miR-200a induction in H2170-ER cells showed significant downregulation of ZEB-1 (3 fold) at 72 hr and an upregulation of E-cadherin (2 fold) when compared to the mock transfected cells. Morphological changes indicative of EMT were detected using immunofluorescence with Vimentin and E-Cadherin antibodies, which displayed upregulation of Vimentin filaments (2 fold) and downregulation of E-Cadherin (3 fold) in H2170-ER and H2170-SR cells when compared to H2170-P cells. We then conducted experiments where we suppressed ZEB-1 by inducing miR-200a in TKI resistant cells. The immunoblotting results suggested recovery of E-Cadherin, and downregulation of ZEB-1 and N-Cadherin in TKI resistant cells. We also observed increased sensitivity towards erlotinib and SU11274 by 20-25%. Additionally, we observed decrease in levels of β-Catenin and upon siRNA knockdown of β-Catenin, suppression of levels of ZEB-1. This indicates a direct correlation between nuclear accumulation of β-Catenin and occurrence of EMT in TKI resistant cells by increase in expression of ZEB-1.

Our results indicate that increased activation of Wnt/β-Catenin pathway in the TKI resistant NSCLC cells is due to the EMT. In NSCLC patients, L858R and T790M mutations are associated with TKI resistance which could be responsible for inducing EMT. We are further studying cell lines with EGFR mutations to determine their role in induction of EMT this may provide clinicians with novel targets to overcome TKI resistance in NSCLC patients.

Citation Format: Ichwaku Rastogi, Tsatsral Iderzorig, Gagan Chhabra, Gregory M. Botting, Andrew Webb, Brad Foster, Brian Webb, Marie Nlend, Neelu Puri. Epithelial mesenchymal transition and its role in TKI resistant NSCLC cell lines. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1599.

Abstract 4755: Correlation of expression of EGFR, cMET and mTOR signaling pathway proteins with each other and their impact on prognosis in non-small cell lung cancer patients

NSCLC tumors acquire resistance to EGFR-TKIs, and studies have suggested that co-localization of c-MET and EGFR may be a modality of acquired resistance. Upregulation of alternative signaling pathways such as Wnt or mTOR have been shown to be associated with poor prognosis and are a potential mechanism of resistance. This study aims at examining these signaling pathways and EGFR/c-MET co-expression in 100 patients with stage I-IV NSCLC. We have data on 50 patients, and are working on the remaining samples. Tumor tissue from biopsies or resections have been obtained with IRB approval, processed, sectioned, and mounted on microscope slides. Total and active forms of EGFR, c-MET, mTOR, S6K, beta-catenin, and Axin2 were detected using singleplex or multiplex IHC staining procedures, and stains were graded by an independent pathologist using a validated scoring system. We selected Stage IV NSCLC (n = 32) patients to correlate EGFR/c-MET expression with overall survival, and analyzed them for months to mortality based on high or low EGFR expression. Patients with high EGFR expression (n = 16) showed lower overall survival compared to those with low EGFR expression (n = 16). Expression of c-MET is linked to decreased survival in Stage IV NSCLC patients (n = 4). Patients with EGFR/c-MET co-localization (n = 19) showed decreased overall survival compared to patients without EGFR/c-MET co-localization (n = 9). Elevated mTOR and p-mTOR are associated with worse prognosis in Stage IV NSCLC patients. Patients categorized with either low mTOR expression (n = 10) or high mTOR expression (n = 19) showed increased mortality with high mTOR expression (5.9 months) compared to patients with low mTOR expression (13.5 months). A similar trend was seen in patients with either low (n = 4, 7.5 months) or high (n = 24, 15.9 months) p-mTOR expression. Patients with low beta-catenin expression (n = 4) showed improved survival in comparison to patients with high beta-catenin expression (n = 18), 9.4 months vs 6.3 months, respectively. To determine correlations in expression of these proteins we found that EGFR/c-MET co-expression is inversely correlated with active beta-catenin and directly correlated with a negative regulator of beta-catenin, Axin-2 suggesting EGFR/c-MET co-expression is associated with a downregulation of Wnt activity. In contrast, elevated EGFR/c-MET co-expression and co-activation is statistically significantly correlated with elevated mTOR-S6K expression and activation suggesting EGFR/c-MET co-expression is associated with an upregulation of the mTOR pathway activity. Elevated mTOR pathway activation at the time of diagnosis is statistically significantly associated with poor prognosis in patients with stage IV NSCLC. These preliminary results suggest that mTOR inhibition therapy in addition to EGFR/c-MET inhibition therapies may be beneficial in this population.

Citation Format: Zachary Crees, Caleb Shearrow, Leo Lin, Jennifer Girard, Kavin Arasi, Aayush Bhoraskar, Andrew Nowak, Bonnie Sheu, Gagan Chhabra, Shylendra Sreenivassappa, Connie Vitali, Odile David, Neelu Puri. Correlation of expression of EGFR, cMET and mTOR signaling pathway proteins with each other and their impact on prognosis in non-small cell lung cancer patients. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4755.

Mechanism of c-Met and EGFR tyrosine kinase inhibitor resistance through epithelial mesenchymal transition in non-small cell lung cancer

According to currently available estimates from Cancer Research UK, 14.1 million new lung cancer cases were diagnosed and a staggering 8.2 million people worldwide died from lung cancer in 2012. EGFR and c-Met are two tyrosine kinase receptors most commonly overexpressed or mutated in Non-small Cell Lung Cancer (NSCLC) resulting in increased proliferation and survival of lung cancer cells. Tyrosine kinase inhibitors (TKIs), such as erlotinib, approved by the FDA as first/second line therapy for NSCLC patients have limited clinical efficacy due to acquired resistance. In this manuscript, we investigate and discuss the role of epithelial mesenchymal transition (EMT) in the development of resistance against EGFR and c-Met TKIs in NSCLC. Our findings show that Zeb-1, a transcriptional repressor of E-Cadherin, is upregulated in TKI-resistant cells causing EMT. We observed that TKI-resistant cells have increased gene and protein expression of EMT related proteins such as Vimentin, N-Cadherin, β-Catenin and Zeb-1, while expression of E-Cadherin, an important cell adhesion molecule, was suppressed. We also confirmed that TKI-resistant cells display mesenchymal cell type morphology, and have upregulation of β-Catenin which may regulate expression of Zeb-1, a transcriptional repressor of E-Cadherin in TKI-resistant NSCLC cells. Finally, we show that down-regulating Zeb-1 by inducing miR-200a or β-Catenin siRNA can increase drug sensitivity of TKI-resistant cells.

Mechanism of Resistance and Novel Targets Mediating Resistance to EGFR and c-Met Tyrosine Kinase Inhibitors in Non-Small Cell Lung Cancer

Tyrosine kinase inhibitors (TKIs) against EGFR and c-Met are initially effective when administered individually or in combination to non-small cell lung cancer (NSCLC) patients. However, the overall efficacies of TKIs are limited due to the development of drug resistance. Therefore, it is important to elucidate mechanisms of EGFR and c-Met TKI resistance in order to develop more effective therapies. Model NSCLC cell lines H1975 and H2170 were used to study the similarities and differences in mechanisms of EGFR/c-Met TKI resistance. H1975 cells are positive for the T790M EGFR mutation, which confers resistance to current EGFR TKI therapies, while H2170 cells are EGFR wild-type. Previously, H2170 cells were made resistant to the EGFR TKI erlotinib and the c-Met TKI SU11274 by exposure to progressively increasing concentrations of TKIs. In H2170 and H1975 TKI-resistant cells, key Wnt and mTOR proteins were found to be differentially modulated. Wnt signaling transducer, active β-catenin was upregulated in TKI-resistant H2170 cells when compared to parental cells. GATA-6, a transcriptional activator of Wnt, was also found to be upregulated in resistant H2170 cells. In H2170 erlotinib resistant cells, upregulation of inactive GSK3β (p-GSK3β) was observed, indicating activation of Wnt and mTOR pathways which are otherwise inhibited by its active form. However, in H1975 cells, Wnt modulators such as active β-catenin, GATA-6 and p-GSK3β were downregulated. Additional results from MTT cell viability assays demonstrated that H1975 cell proliferation was not significantly decreased after Wnt inhibition by XAV939, but combination treatment with everolimus (mTOR inhibitor) and erlotinib resulted in synergistic cell growth inhibition. Thus, in H2170 cells and H1975 cells, simultaneous inhibition of key Wnt or mTOR pathway proteins in addition to EGFR and c-Met may be a promising strategy for overcoming EGFR and c-Met TKI resistance in NSCLC patients.

Clinical Challenges to Current Molecularly Targeted Therapies in Lung Cancer

Lung cancer is difficult to treat with a poor prognosis and a five year survival of 15%. Current molecularly targeted therapies are initially effective in non-small cell lung cancer (NSCLC) patients; however, they are plagued with difficulties including induced resistance and small therapeutically responsive populations. This mini review describes the mechanism of resistance to several molecularly targeted therapies which are currently being used to treat NSCLC. The major targets discussed are c-Met, EGFR, HER2, ALK, VEGFR, and BRAF. The first generation tyrosine kinase inhibitors (TKIs) resulted in resistance; however, second and third generation TKIs are being developed, which are generally more efficacious and have potential to treat NSCLC patients with resistance to first generation TKIs. Combination therapies could also be effective in preventing TKI resistance in NSCLC patients.

Structure modeling and antidiabetic activity of a seed protein of Momordica charantia in non-obese diabetic (NOD) mice

Momordica charantia is a well known medicinal plant used in the traditional medicinal system for the treatment of various diseases including diabetes mellitus. Recently, a novel protein termed as ADMc1 from the seed extract of M. charantia has been identified and isolated showing significant antihyperglycemic activity in type 1 diabetic rats in which diabetes was induced. However, the structure of this protein has not yet been analyzed. Homology modeling approach was used to generate a high quality protein 3D structure for the amino acid sequence of the ADMc1 protein in this study. The comparative assessment of secondary structures revealed ADMc1 as an all-alpha helix protein with random coils. Tertiary structure predicted on the template structure of Napin of B. Napus (PDB ID: 1SM7) with which the ADMc1 showed significant sequence similarity, was validated using protein structure validation tools like PROCHECK, WHAT_CHECK, VERIFY3D and ProSA. Arrangement of disulfide bridges formed by cysteine residues were predicted by the Dianna 1.1 server. The presence of multiple disulfide bond confers the stable nature of the ADMc1 protein. Further, the biological activity of the ADMc1 was assessed in non-obese diabetic (NOD) mice which are spontaneous model of type 1 diabetes. Significant reduction in the blood glucose levels of NOD mice was observed up to 8 h post administration of the rADMc1 protein. Overall, the structural characterizations with antihyperglycemic activity of this seed protein of Momordica charantia demonstrate its potential as an antidiabetic agent.

A case of isolated cutaneous Rosai-Dorfman-Syndrome

Rosai-Dorfman Syndrome (RDD) is a rare, benign, self-limiting disorder which is characterized by the non-malignant proliferation of distinctive histiocytic cell within lymphatic system. RDD has been described as a dynamic entity in the spectrum of histiocytosis with non-Langerhans cell histiocytosis at one end and Langerhans cell histiocytosis at the other. The exact etiology of this disease is uncertain despite widespread search for infectious or immunological reasons. We present a case of purely cutaneous Rosai-Dorfman Syndrome presenting as abdominal wall swelling.

KEYWORDS

Rosai-Dorfman Disease, Lymphoma.

Heterologous expression and biochemical characterization of recombinant alpha phosphoglucomutase from Mycobacterium tuberculosis H37Rv

Phosphoglucomutase (PGM) plays an important role in polysaccharide capsule formation and virulence in a number of bacterial pathogens. However, the enzyme has not yet been characterized from Mycobacterium tuberculosis (Mtb). Here, we report the biochemical properties of recombinant Mtb-PGM as well as the in silico structural analysis from Mtb H37Rv. The purified recombinant enzyme was enzymatically active with a specific activity of 67.5 U/mg and experimental k(cat) of 70.31 s(-1) for the substrate glucose-1-phosphate. The enzyme was stable in pH range 6.5-7.4 and exhibited temperature optima range between 30 and 40°C. Various kinetic parameters and constants of the rPGM were determined. A structural comparison of Modeller generated 3D Mtb-PGM structure with rabbit muscle PGM revealed that the two enzymes share the same overall heart shape and four-domain architecture, despite having only 17% sequence identity. However, certain interesting differences between the two have been identified, which provide an opportunity for designing new drugs to specifically target the Mtb-PGM. Also, in the absence of the crystal structure of the Mtb-PGM, the modeled structure could be further explored for in silico docking studies with suitable inhibitors.

Molecular cloning, sequence analysis and structure modeling of OmpR, the response regulator of Aeromonas hydrophila

The ability of bacteria to survive and proliferate in changing environmental conditions, and during host cell invasion is the key to their pathogenicity. In order to achieve this, the bacteria use a signal transduction system, the two component regulatory system, which consists of a sensor kinase and a response regulator. The EnvZ/OmpR system regulates the porin genes ompF/ompC in response to changes in osmolarity. In the present study, the ompR gene of Aeromonas hydrophila (isolate Ah17) was cloned, sequenced and characterized. Further an attempt was made to analyze the structural characteristics of the OmpR protein from Aeromonas hydrophila. The three dimensional structure of the protein was predicted by homology modeling and the modeled structure was compared to other members of two component response regulators. This study would be helpful for structure based drug design approaches to generate drugs against this harmful pathogen to control its proliferation in both human and fish hosts.

DNA polymerase III α subunit from Mycobacterium tuberculosis H37Rv: Homology modeling and molecular docking of its inhibitor

The alpha subunit of Mycobacterial DNA polymerase III holo enzyme catalyzes the polymerization of both DNA strands. The present investigation reports three dimensional (3-D) structure model of DNA polymerase III α subunit of Mycobacterium tuberculosis H37Rv (MtbDnaE1) generated using homology modeling with the backbone structure of DNA polymerase III α of Thermus aquaticus as a template. The model was evaluated at various structure verification servers, which assess the stereo chemical parameters of the residues in the model, as well as structural and functional domains. Comparative analysis of MtbDnaE1 structure reveals the structure of its catalytic domain to be unrelated to that of the human. Successful docking of known inhibitor of bacterial DNA polymerases, 251D onto the modeled MtbDnaE1 was also performed. Therefore, the structure model of MtbDnaE1, a potential anti-mycobacterial target, opens a new avenue for structure-based drug designing against the pathogen.

ABBREVIATIONS

aa - amino acid(s), PolIIIα - DNA polymerase III alpha subunit, Taq Pol IIIα - Pol IIIα of Thermus aquaticus, MtbDnaE1 - PolIIIα of Mycobacterium tuberculosis.

Identification and modeling of a drug target for Clostridium perfringens SM101

In the present study, comparative genome analysis between Clostridium perfringens and the human genome was carried out to identify genes that are essential for the pathogen's survival, and non-homologous to the genes of human host, that can be used as potential drug targets. The study resulted in the identification of 426 such genes. The number of these potential drug targets thus identified is significantly lower than the genome's protein coding capacity (2558 protein coding genes). The 426 genes of C. perfringens were further analyzed for overall similarities with the essential genes of 14 different bacterial species present in Database of Essential Genes (DEG). Our results show that there are only 5 essential genes of C. perfringens that exhibit similarity with 12 species of the 14 different bacterial species present in DEG database. Of these, 1 gene was similar in 12 species and 4 genes were similar in 11 species. Thus, the study opens a new avenue for the development of potential drugs against the highly pathogenic bacterium. Further, by selecting these essential genes of C. perfringens, which are common and essential for other pathogenic microbial species, a broad spectrum anti-microbial drug can be developed. As a case study, we have built a homology model of one of the potential drug targets, ABC transporter-ATP binding protein, which can be employed for in silico docking studies by suitable inhibitors.

Molecular cloning, sequence analysis and homology modeling of galE encoding UDP-galactose 4-epimerase of Aeromonas hydrophila

A. hydrophila, a ubiquitous gram-negative bacterium present in aquatic environments, has been implicated in illness in humans, fish and amphibians. Lipopolysaccharides (LPS), a surface component of the outer membrane, are one of the main virulent factors of gram-negative bacteria. UDP-galactose 4-epimerase (GalE) catalyses the last step in the Leloir pathway of galactose metabolism and provides precursor for the biosynthesis of extracellular LPS and capsule. Due to its key role in LPS biosynthesis, it is a potential drug target. The present study describes cloning, sequence analysis and prediction of three dimensional structure of the deduced amino acid sequence of the galE of A. hydrophila AH17. The cloned galE consists of the putative promoter-operator region, and an open reading frame of 338 amino acid residues. Sequence alignment and predicted 3Dstructure revealed that the GalE of A. hydrophila consists of the signature sequences of the epimerase super family. The present study reports the molecular modeling / 3D-structure prediction of GalE of A. hydrophila. Further, the potential regions of the enzyme that can be targeted for drug design are identified.