A Novel Pan-RAS Inhibitor with a Unique Mechanism of Action Blocks Tumor Growth in Mouse Models of GI Cancer

Here we characterize a novel pan-RAS inhibitor, ADT-007, that potently and selectively inhibited the growth of histologically diverse cancer cell lines with mutant or activated RAS irrespective of the RAS mutation or isozyme. Growth inhibition was dependent on activated RAS and associated with reduced GTP-RAS levels and MAPK/AKT signaling. ADT-007 bound RAS in lysates from sensitive cells with sub-nanomolar EC 50 values but did not bind RAS in lysates from insensitive cells with low activated RAS. Insensitivity to ADT-007 was attributed to metabolic deactivation by UGT-mediated glucuronidation, providing a detoxification mechanism to protect normal cells from pan-RAS inhibition. Molecular modeling and experiments using recombinant RAS revealed that ADT-007 binds RAS in a nucleotide-free conformation to block GTP activation. Local injection of ADT-007 strongly inhibited tumor growth in syngeneic immune competent and xenogeneic immune deficient mouse models of colorectal and pancreatic cancer and activated innate and adaptive immunity in the tumor microenvironment.

SIGNIFICANCE

ADT-007 is a novel pan-RAS inhibitor with a unique mechanism of action having potential to circumvent resistance to mutant-specific KRAS inhibitors and activate antitumor immunity. The findings support further development of ADT-007 analogs and/or prodrugs with oral bioavailability as a generalizable monotherapy or combined with immunotherapy for RAS mutant cancers.

BACKGROUND

It is projected that colorectal cancer (CRC) and pancreatic ductal adenocarcinoma (PDA) will cause 52,580 and 49,830 deaths in the US in 2023, respectively (1). The 5-year survival rates for CRC and PDA are 65% and 12%, respectively (1). Over 50% of CRC and 90% of PDA patients harbor mutations in KRAS genes that are associated with poor prognosis, making the development of novel KRAS inhibitors an urgent unmet medical need (2).

Cancer-associated mesothelial cells are regulated by the anti-Müllerian hormone axis

Cancer-associated mesothelial cells (CAMCs) in the tumor microenvironment are thought to promote growth and immune evasion. We find that, in mouse and human ovarian tumors, cancer cells express anti-Müllerian hormone (AMH) while CAMCs express its receptor AMHR2, suggesting a paracrine axis. Factors secreted by cancer cells induce AMHR2 expression during their reprogramming into CAMCs in mouse and human in vitro models. Overexpression of AMHR2 in the Met5a mesothelial cell line is sufficient to induce expression of immunosuppressive cytokines and growth factors that stimulate ovarian cancer cell growth in an AMH-dependent way. Finally, syngeneic cancer cells implanted in transgenic mice with Amhr2-/- CAMCs grow significantly slower than in wild-type hosts. The cytokine profile of Amhr2-/- tumor-bearing mice is altered and their tumors express less immune checkpoint markers programmed-cell-death 1 (PD1) and cytotoxic T lymphocyte-associated protein 4 (CTLA4). Taken together, these data suggest that the AMH/AMHR2 axis plays a critical role in regulating the pro-tumoral function of CAMCs in ovarian cancer.

Metronomic Administration of Topotecan Alone and in Combination with Docetaxel Inhibits Epithelial-mesenchymal Transition in Aggressive Variant Prostate Cancers

Prostate cancer is the second leading cause of noncutaneous cancer-related deaths in American men. Androgen deprivation therapy (ADT), radical prostatectomy, and radiotherapy remain the primary treatment for patients with early-stage prostate cancer (castration-sensitive prostate cancer). Following ADT, many patients ultimately develop metastatic castration-resistant prostate cancer (mCRPC). Standard chemotherapy options for CRPC are docetaxel (DTX) and cabazitaxel, which increase median survival, although the development of resistance is common. Cancer stem-like cells possess mesenchymal phenotypes [epithelial-to-mesenchymal transition (EMT)] and play crucial roles in tumor initiation and progression of mCRPC. We have shown that low-dose continuous administration of topotecan (METRO-TOPO) inhibits prostate cancer growth by interfering with key cancer pathway genes. This study utilized bulk and single-cell or whole-transcriptome analysis [(RNA sequencing (RNA-seq) and single-cell RNA sequencing (scRNA-seq)], and we observed greater expression of several EMT markers, including Vimentin, hyaluronan synthase-3, S100 calcium binding protein A6, TGFB1, CD44, CD55, and CD109 in European American and African American aggressive variant prostate cancer (AVPC) subtypes-mCRPC, neuroendocrine variant (NEPC), and taxane-resistant. The taxane-resistant gene FSCN1 was also expressed highly in single-cell subclonal populations in mCRPC. Furthermore, metronomic-topotecan single agent and combinations with DTX downregulated these EMT markers as well as CD44+ and CD44+/CD133+ "stem-like" cell populations. A microfluidic chip-based cell invasion assay revealed that METRO-TOPO treatment as a single agent or in combination with DTX was potentially effective against invasive prostate cancer spread. Our RNA-seq and scRNA-seq analysis were supported by in silico and in vitro studies, suggesting METRO-TOPO combined with DTX may inhibit oncogenic progression by reducing cancer stemness in AVPC through the inhibition of EMT markers and multiple oncogenic factors/pathways.

Significance

The utilization of metronomic-like dosing regimens of topotecan alone and in combination with DTX resulted in the suppression of makers associated with EMT and stem-like cell populations in AVPC models. The identification of molecular signatures and their potential to serve as novel biomarkers for monitoring treatment efficacy and disease progression response to treatment efficacy and disease progression were achieved using bulk RNA-seq and single-cell-omics methodologies.

Abstract 4937: Immunoproteasome inhibitors for the treatment of t(4;11)-driven ALL

The t(4;11)(q21;q23) chromosomal translocation that creates the MLL-AF4 fusion protein, confers a poor prognosis in infant acute lymphoblastic leukemia (ALL). This translocation also sensitizes cells to proteasome inhibitors bortezomib and carfilzomib, which are approved by the FDA for the treatment of multiple myeloma. Clinical activity of bortezomib in combination with standard chemotherapy has been documented in several clinical trials of ALL patients, and a case of a single-agent activity against relapsed leukemia driven by the MLL-AF4 translocation has been described. However, toxicities of bortezomib and carfilzomib may be unacceptable to pediatric patients. We found that the overwhelming majority of proteasomes in this subtype of ALL are lymphoid tissue specific immunoproteasomes. Cells with MLL-AF4 translocations were sensitive to pharmacologically relevant concentrations of specific immunoproteasome inhibitors ONX-0914 and M3258. Furthermore, both compounds dramatically delayed growth of orthotopic xenograft tumors in mice. Thus, immunoproteasomes are therapeutic targets in ALL and replacing bortezomib and carfilzomib with immunoproteasome inhibitors in ALL should reduce toxicities associated with inhibition of the proteasomes in non-lymphoid tissues.

Citation Format: Alexei F. Kisselev, Tyler W. Jenkins, Elise Fitzerald, Andrey V. Maksimenko, Peter Panizzi, Jennifer L. Fields, Steven N. Fiering, Amit K. Mitra. Immunoproteasome inhibitors for the treatment of t(4;11)-driven ALL. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4937.

Polygenic Ara-C Response Score Identifies Pediatric Patients With Acute Myeloid Leukemia in Need of Chemotherapy Augmentation

PURPOSE

To establish a patient-specific polygenic score derived from cytarabine (ara-C) pathway pharmacogenomic evaluation to personalize acute myeloid leukemia (AML) treatment.

MATERIALS AND METHODS

Single nucleotide polymorphisms (SNPs) in the ara-C-pathway genes were analyzed with outcome in patients from the multicenter-AML02 trial (N = 166). Multi-SNP predictor modeling was used to develop 10-SNP Ara-C_SNP score (ACS10) using top SNPs predictive of minimal residual disease and event-free survival (EFS) from the AML02-cohort and four SNPs previously associated with ara-C triphosphate levels in the AML97 trial. ACS10 was evaluated for association with outcomes in each clinical trial arms: the standard low-dose ara-C (LDAC, n = 91) and augmented high-dose ara-C (HDAC, n = 75) arms of AML02 and the standard Ara-C, daunorubicin and etoposide (ADE) (n = 465) and the augmented ADE + gemtuzumab ozogamicin (GO; n = 466) arms of AAML0531 trial.

RESULTS

In the standard LDAC-arm of AML02 cohort, the low-ACS10 score group (≤ 0) had significantly worse EFS (ACS10 low v high hazard ratio [HR] = 2.81; 95% CI, 1.45 to 5.43; P = .002) and overall survival (OS; HR = 2.98; 95% CI, 1.32 to 6.75; P = .009) compared with the high-ACS10 group (score > 0). These results were validated in the standard-ADE arm of AAML0531, with poor outcome in the low-ASC10 group compared with the high-ACS10 group (EFS: HR = 1.35, 95% CI, 1.04 to 1.75, P = .026; OS: HR = 1.64, 95% CI, 1.2 to 2.22, P = .002). Within the augmented arms (AML02-HDAC and AAML0531-ADE + GO), EFS and OS did not differ between low- and high-ACS10 score groups. In both cohorts, patients with low-ACS10 consistently showed a 10-percentage point improvement in 5-year EFS with augmented therapy (AML02-HDAC or AAML0531-ADE + GO arms) than with standard therapy (AML02-LDAC or AAML0531-ADE arms).

CONCLUSION

Patients with low-ACS10 score experienced significantly poor outcome when treated on standard regimen. Augmentation with either high-dose ara-C or GO addition improved outcome in low-ACS10 group. A polygenic ACS10 score can identify patients with unfavorable pharmacogenetic characteristics and offers a potential for an elective augmented therapy option.

Abstract PO-126: Identification of distinct mRNA & microRNA signatures and mRNA-miRNA pairs associated with inter-ethnic differences in prostate cancer aggressiveness

Introduction: The incidence of aggressive prostate cancer (PCa) and mortality is disproportionately higher in men of African-American (AA) ancestry. Treatment options for these patients are docetaxel or cabazitaxel alone or in combination with bevacizumab, thalidomide, and prednisone or immunotherapy. However, these chemotherapeutics typically only improve survival slightly (3-4 months). Further, majority of patients develop metastatic PCa over time, resistant to conventional chemotherapy (metastatic castration resistance PCa or mCRPC). Therefore, an understanding of the molecular mechanisms underlying the ethnic differences in disease aggressiveness and progression in PCa is needed. Methods: In this study, we performed mRNA and miRNA expression (RNAseq) analysis on PCa cell lines representing different tumor types (aggressive androgen receptor (AR) nonresponsive AR- vs. non-aggressive AR+) and derived from patients with European American/EA (PC3, PC3M, DU145, DUTXR, 22RV1, LNCaP, VCaP, LaPC4, C4, C4-2B) and AA (MDA-Pca-2b, RC77, RC165, RC43) ancestry to identify differentially expressed genes (DEG) associated with tumor aggressiveness and ethnicity. Next, we validated the top DEG signatures using an AA vs EA patient cohort dataset as well as in silico validation using The Cancer Genome Atlas (TCGA) database. For each miRNA, functional analysis was performed using miRBase datasets and mRNA-miRNA pairs and binding sites were predicted by TargetScan. Finally, IPA (Ingenuity Pathway Analysis) was performed to identify key regulators and downstream effects on biological and disease processes based on the expression patterns of DEGs. Results: We identified distinct mRNA and miRNA expression signatures associated with aggressive vs. non-aggressive PCa of EA vs. AA origin. The top DEGs that were associated with patient survival (p< 0.0001), stratified by Gleason scores, were PLAU, TGFB1, SERPINE1, MET, TIPM1, ITGA3, SERPINB5, PLAUR, MMPs, CDKN1A, and IGF1. The transporter genes SLC25A, SLC16A, and ABCB6 were also identified as important markers of aggressiveness. Notably, PLAU, MCAM, MET, TIMP1 were top DEGs in AA vs EA cell lines while SERPINE1 and MCAM were DEGs in AA vs EA patient cohort. IPA identified the activation of the angiogenesis pathway as a crucial factor for cancer aggressiveness. Top predicted miRNA-mRNA pairs included SERPINE1-let7, PLAU- mir181 which potentially influence differential gene expression in late-stage cancers. Finally, our immunoblotting results confirmed the protein expression changes of top DEGs. Next, we plan to perform CRISPR-based gene editing to functionally validate the molecular (mRNA/miRNA) signatures. Conclusion: An -omics-based approach was used to identify genetic signatures that provide insights into the molecular basis of PCa aggressiveness between men of EA vs AA ancestry. We believe this strategy will aid in developing effective targeted ethnicity-specific personalized treatment schedules for aggressive forms of PCa. This promises to address the known health disparity that is observed in AA men.

Citation Format: Taraswi Mitra Ghosh, Jason White, Suman Mazumder, Joshua Davis, Grace Hurley, Brian Cummings, Gary Piazza, Amit K Mitra, Clayton Yates, Robert Arnold. Identification of distinct mRNA & microRNA signatures and mRNA-miRNA pairs associated with inter-ethnic differences in prostate cancer aggressiveness [abstract]. In: Proceedings of the AACR Virtual Conference: 14th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2021 Oct 6-8. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2022;31(1 Suppl):Abstract nr PO-126.

Identification and Characterization of Key Differentially Expressed Genes Associated With Metronomic Dosing of Topotecan in Human Prostate Cancer

Repetitive, low-dose (metronomic; METRO) drug administration of some anticancer agents can overcome drug resistance and increase drug efficacy in many cancers, but the mechanisms are not understood fully. Previously, we showed that METRO dosing of topotecan (TOPO) is more effective than conventional (CONV) dosing in aggressive human prostate cancer (PCa) cell lines and in mouse tumor xenograft models. To gain mechanistic insights into METRO-TOPO activity, in this study we determined the effect of METRO- and CONV-TOPO treatment in a panel of human PCa cell lines representing castration-sensitive/resistant, androgen receptor (+/−), and those of different ethnicity on cell growth and gene expression. Differentially expressed genes (DEGs) were identified for METRO-TOPO therapy and compared to a PCa patient cohort and The Cancer Genome Atlas (TCGA) database. The top five DEGs were SERPINB5, CDKN1A, TNF, FOS, and ANGPT1. Ingenuity Pathway Analysis predicted several upstream regulators and identified top molecular networks associated with METRO dosing, including tumor suppression, anti-proliferation, angiogenesis, invasion, metastasis, and inflammation. Further, the top DEGs were associated with increase survival of PCa patients (TCGA database), as well as ethnic differences in gene expression patterns in patients and cell lines representing African Americans (AA) and European Americans (EA). Thus, we have identified candidate pharmacogenomic biomarkers and novel pathways associated with METRO-TOPO therapy that will serve as a foundation for further investigation and validation of METRO-TOPO as a novel treatment option for prostate cancers.

Abstract 1355: A novel andrographolide analogue (3A.1) synergizes with Taxane derivatives in aggressive metastatic prostate cancers through upregulation of heatshock proteins and downregulation of MAT2A-mediated cell migration and invasion

BACKGROUND: Prostate cancer (PCa) is the 2nd leading cause of non-cutaneous cancer deaths among men in the USA with many progressing to aggressive metastatic castration resistant PCa (mCRPC; PCa unresponsive to androgen deprivation). Conventional treatment with taxanes (TX; docetaxel (DTX) or cabazitaxel (CBZ)) increases survival rates only slightly. The andrographolide analog, 19-tert-butyldiphenylsilyl-8,7-epoxy andrographolide (3A.1) has shown anticancer activity against various cancers. In this study, we investigated the effect of 3A.1 alone and in combination with DTX and CBZ against models of aggressive PCa.

METHODS: Androgen receptor negative (AR-ve) mCRPC cell lines were treated with CBZ, DTX and 3A.1 as single-agent or combination over a broad concentration range, and in vitro cytotoxicity was determined. Chou-Talalay's combination index (CI) theorem was used to determine synergism and predicted dose reduction of taxanes. Post-treatment effect of single-agent and combination regimens on gene expression profile (GEP) was assessed using mRNA sequencing. Differentially expressed genes (DEGs) and molecular pathways involved in 3A.1 mechanism of action and drug synergy were identified using DESeq2, edgeR and Ingenuity pathway analysis (IPA). Protein expression of top DE genes was confirmed by immunoblotting. Cell cycle analysis, scratch/wound healing, and COMET assays were used to functionally validate the top treatment-associated genes.

RESULTS: Exposure to 3A.1 alone exhibited a dose- and time-dependent antitumor activity in mCRPC. CI values of all 3A.1+ TX combinations were less than 0.5, indicating synergism. Co-treatment of 3A.1 with TX reduced the required dose of DTX by 9.5 to 18-folds (p<0.05), and CBZ by 3 to 14-folds (p<0.05). Our caspase 3/7 assay (apoptosis) results agreed with in vitro cytotoxicity data. RNAseq followed by IPA analysis identified that the top treatment-induced DEGs belong to cell migration, growth, apoptosis (MMP1, HSPB1, PSRC1), protein ubiquitination (HNRNPH2, HSPA1A/HSPA1B), and DNA repair (H2BC4, 11) pathways, along with cancer progression. Most importantly, our top downregulated DEG was MAT2A which has earlier been shown to be involved in cell migration and invasion. Our analysis using Immunoblotting, COMET, and Wound healing/Scratch (cell migration) assays corroborated with these findings. Finally, using in silico analysis on the TCGA (The Cancer Genome Atlas) database, we found that MAT2A and highly co-expressed (r>0.7) genes, TRA2B and SF1, were associated with worser Gleason score and nodal metastasis status in prostate adenocarcinoma patients (PRAD-TCGA).

CONCLUSION: These results suggest that 3A.1 may be useful in increasing the anticancer efficacy of taxanes to treat aggressive prostate cancer.

Citation Format: Taraswi Mitra Ghosh, Teeratas Kansom, Suman Mazumder, Joshua Davis, Ahmed Alnaim, Aedan Bird, P Opanasopit, Amit K. Mitra, Robert Arnold. A novel andrographolide analogue (3A.1) synergizes with Taxane derivatives in aggressive metastatic prostate cancers through upregulation of heatshock proteins and downregulation of MAT2A-mediated cell migration and invasion [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1355.

Target highlights in CASP13: Experimental target structures through the eyes of their authors

The functional and biological significance of selected CASP13 targets are described by the authors of the structures. The structural biologists discuss the most interesting structural features of the target proteins and assess whether these features were correctly reproduced in the predictions submitted to the CASP13 experiment.

Abstract 5402: Single cell sequencing of high grade serous ovarian cancer

We performed RNA sequencing of single cells derived from a high grade serous ovarian cancer (HGSOC) specimen to determine the extent of heterogeneity and to determine if it was feasible to identify cancer stem cells or gene expression signatures of chemo resistance. To perform RNA sequencing we enzymatically digested a fresh specimen from an HGSOC derived from the ovary. Immune cells were depleted by flow cytometry and single cell sequencing was performed using the Fluidigm C1 chip in tandem with Illumina HiSeq 2500 sequencing. Multiple bioinformatics tools were used to identify subgroups and activated pathways. Immunohistochemistry was performed on an adjacent tumor section to analyze markers of epithelium, stroma and stem cells. We found that gene expression patterns in single cells could be used to separate cells into stroma-like and epithelial-like groups. Gene set enrichment analysis identified proliferative genesets (oxidative phosphorylation and MYC targets) associated with the epithelial-like cells while epithelial-to-mesenchymal-transition (EMT) genes associated with the stroma-like cells. Neither group was significantly associated with genesets derived from chemo-resistant cells. Using known marker analysis, we could identify a small percentage of cells that expressed ovarian cancer stem cell markers and we could group cells into functional categories. Using four molecular subtypes established from large-scale bulk sequencing studies we show that single cells from a single patient are heterogeneous and each molecular subtype is represented. In conclusion, we show the feasibility of performing single cell sequencing on an epithelial ovarian cancer and reveal a heterogeneous population of cells. Expanding these findings to a larger cohort of patients could allow for identification of targetable sub-populations of cells that were previously undetectable in studies that use bulk samples to interrogate the transcriptome and genome of ovarian cancer patients.

Citation Format: Timothy K. Starr, Boris Winterhoff, Makayla Maile, Kenneth Beckman, Jerry Daniel, Melissa Geller, Martina Bazzaro, Molly Klein, Raffaele Hellweg, Juan Abrahante, Amit K. Mitra, Atilla Sebe, Sally A. Mullany. Single cell sequencing of high grade serous ovarian 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 5402. doi:10.1158/1538-7445.AM2017-5402

Glutaminase inhibitor CB-839 synergizes with carfilzomib in resistant multiple myeloma cells

Curative responses in the treatment of multiple myeloma (MM) are limited by the emergence of therapeutic resistance. To address this problem, we set out to identify druggable mechanisms that convey resistance to proteasome inhibitors (PIs; e.g., bortezomib), which are cornerstone agents in the treatment of MM. In isogenic pairs of PI sensitive and resistant cells, we observed stark differences in cellular bioenergetics between the divergent phenotypes. PI resistant cells exhibited increased mitochondrial respiration driven by glutamine as the principle fuel source. To target glutamine-induced respiration in PI resistant cells, we utilized the glutaminase-1 inhibitor, CB-839. CB-839 inhibited mitochondrial respiration and was more cytotoxic in PI resistant cells as a single agent. Furthermore, we found that CB-839 synergistically enhanced the activity of multiple PIs with the most dramatic synergy being observed with carfilzomib (Crflz), which was confirmed in a panel of genetically diverse PI sensitive and resistant MM cells. Mechanistically, CB-839 enhanced Crflz-induced ER stress and apoptosis, characterized by a robust induction of ATF4 and CHOP and the activation of caspases. Our findings suggest that the acquisition of PI resistance involves adaptations in cellular bioenergetics, supporting the combination of CB-839 with Crflz for the treatment of refractory MM.

Fine-Mapping of 18q21.1 Locus Identifies Single Nucleotide Polymorphisms Associated with Nonsyndromic Cleft Lip with or without Cleft Palate

Nonsyndromic cleft lip with or without cleft palate (NSCL/P) is one of the most common congenital birth defects. NSCL/P is a complex multifactorial disease caused by interactions between multiple environmental and genetic factors. However, the causal single nucleotide polymorphism (SNP) signature profile underlying the risk of familial NSCL/P still remains unknown. We previously reported a 5.7-Mb genomic region on chromosome 18q21.1 locus that potentially contributes to autosomal dominant, low-penetrance inheritance of NSCL/P. In the current study, we performed exome sequencing on 12 familial genomes (six affected individuals, two obligate carriers, and four seemingly unaffected individuals) of a six-generation family to identify candidate SNPs associated with NSCL/P risk. Subsequently, targeted bidirectional DNA re-sequencing of polymerase chain reaction (PCR)-amplified high-risk regions of MYO5B gene and sequenom iPLEX genotpying of 29 candidate SNPs were performed on a larger set of 33 members of this NSCL/P family (10 affected + 4 obligate carriers + 19 unaffected relatives) to find SNPs significantly associated with NSCL/P trait. SNP vs. NSCL/P association analysis showed the MYO5B SNP rs183559995 GA genotype had an odds ratio of 18.09 (95% Confidence Interval = 1.86–176.34; gender-adjusted P = 0.0019) compared to the reference GG genotype. Additionally, the following SNPs were also found significantly associated with NSCL/P risk: rs1450425 (LOXHD1), rs6507992 (SKA1), rs78950893 (SMAD7), rs8097060, rs17713847 (SCARNA17), rs6507872 (CTIF), rs8091995 (CTIF), and rs17715416 (MYO5B). We could thus identify mutations in several genes as key candidate SNPs associated with the risk of NSCL/P in this large multi-generation family.

FDA Approval Summary: Lenvatinib for Progressive, Radio-iodine-Refractory Differentiated Thyroid Cancer

The FDA approved lenvatinib (Lenvima, Eisai Inc.) for the treatment of patients with locally recurrent or metastatic, progressive, radioactive iodine-refractory (RAI-refractory) differentiated thyroid cancer (DTC). In an international, multicenter, double-blinded, placebo-controlled trial (E7080-G000-303), 392 patients with locally recurrent or metastatic RAI-refractory DTC and radiographic evidence of disease progression within 12 months prior to randomization were randomly allocated (2:1) to receive either lenvatinib 24 mg orally per day (n = 261) or matching placebo (n = 131) with the option for patients on the placebo arm to receive lenvatinib following independent radiologic confirmation of disease progression. A statistically significant prolongation of progression-free survival (PFS) as determined by independent radiology review was demonstrated [HR, 0.21; 95% confidence interval (CI), 0.16-0.28; P < 0.001, stratified log-rank test], with an estimated median PFS of 18.3 months (95% CI, 15.1, NR) in the lenvatinib arm and 3.6 months (95% CI, 2.2-3.7) in the placebo arm. The most common adverse reactions, in order of decreasing frequency, observed in the lenvatinib-treated patients were hypertension, fatigue, diarrhea, arthralgia/myalgia, decreased appetite, decreased weight, nausea, stomatitis, headache, vomiting, proteinuria, palmar-plantar erythrodysesthesia syndrome, abdominal pain, and dysphonia. Adverse reactions led to dose reductions in 68% of patients receiving lenvatinib at the 24 mg dose and 18% of patients discontinued lenvatinib for adverse reactions leading to residual uncertainty regarding the optimal dose of lenvatinib.

Abstract AS23: Microenvironment mediated downregulation of miR-193b promotes ovarian cancer metastasis

The cross-talk between ovarian cancer cells with the microenvironment of the site of metastasis is an essential determinant of successful metastatic colonization. microRNAs have been well established to play critical roles in various stages of cancer progression, including metastasis. However, the role of the signals from the microenvironment in regulating key microRNAs in metastasizing cancer cells has not been studied. Using a 3D culture model mimicking the human omentum, one of the principal sites of ovarian cancer metastasis, we have identified the microenvironment-induced downregulation of a tumor suppressor microRNA miR-193b in the metastasizing ovarian cancer cells. The direct interaction of the ovarian cancer cells with the mesothelial cells covering the surface of the omentum caused DNA methyltransferase 1 (DNMT1) mediated methylation and decreased expression of miR-193b. The reduction in miR-193b enabled the metastasizing cancer cells to invade and proliferate in the omentum both in vitro and in a mouse xenograft model of ovarian cancer metastasis. The functional effects of miR-193b were mediated at least partly through the concomitant increased expression of its target urokinase-type plasminogen activator (uPA). Our findings link paracrine signals from the microenvironment with the regulation of a key microRNA in cancer cells that is essential for the initial steps of ovarian cancer metastatic colonization. Targeting miR-193b would be a promising approach to treat ovarian cancer metastasis.

Citation Format: AK Mitra, CY Chiang, P Tiwari, ME Peter, E Lengyel. Microenvironment mediated downregulation of miR-193b promotes ovarian cancer metastasis [abstract]. In: Proceedings of the 10th Biennial Ovarian Cancer Research Symposium; Sep 8-9, 2014; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(16 Suppl):Abstract nr AS23.

Microenvironment-induced downregulation of miR-193b drives ovarian cancer metastasis

The cross-talk between ovarian cancer (OvCa) cells and the metastatic microenvironment is an essential determinant of successful colonization. Micro(mi)RNAs play several critical roles during metastasis; however, the role of microenvironmental cues in the regulation of miRNAs in metastasizing cancer cells has not been studied. Using a 3D culture model that mimics the human omentum, one of the principal sites of OvCa metastasis, we identified and characterized the microenvironment-induced downregulation of a tumor suppressor miRNA, miR-193b, in metastasizing OvCa cells. The direct interaction of the OvCa cells with mesothelial cells, which cover the surface of the omentum, caused a DNA methyltransferase 1 (DNMT1) mediated decrease in the expression of miR-193b. The reduction in miR-193b enabled the metastasizing cancer cells to invade and proliferate into human omental pieces ex vivo and into the omentum of a mouse xenograft model of OvCa metastasis. The functional effects of miR-193b were mediated, in large part, by the concomitant increased expression of its target, urokinase-type plasminogen activator (uPA), a known tumor-associated protease. These findings link paracrine signals from the microenvironment with the regulation of a key miRNA that is essential for the initial steps of OvCa metastatic colonization. Targeting miR-193b could prove effective in the treatment of OvCa metastasis.

A novel packing arrangement of AcrB in the lipid bilayer membrane

The central component AcrB of the Escherichia coli drug efflux complex AcrA-AcrB-TolC has been extensively investigated by X-ray crystallography of detergent-protein 3-D crystals. In these crystals, AcrB packs as trimers - the functional unit. We visualized the AcrB-AcrB interaction in its native environment by examining E. coli lipid reconstituted 2-D crystals, which were overwhelmingly formed by asymmetric trimers stabilized by strongly-interacting monomers from adjacent trimers. Most interestingly, we observed lattices formed by an arrangement of AcrB monomers distinct from that in traditional trimers. This hitherto unobserved packing, might play a role in the biogenesis of trimeric AcrB.

RRM1 and RRM2 pharmacogenetics: association with phenotypes in HapMap cell lines and acute myeloid leukemia patients

BACKGROUND

Ribonucleotide reductase catalyzes an essential step in the cellular production of deoxyribonucleotide triphosphates and has been associated with clinical outcome in cancer patients receiving nucleoside analog-based chemotherapy.

MATERIALS & METHODS

In the current study, we sequenced the genes RRM1 and RRM2 in genomic DNA from HapMap cell lines with European (Utah residents with northern and western European ancestry [CEU]; n = 90) or African (Yoruba people in Ibadan, Nigeria [YRI]; n = 90) ancestry.

RESULTS

We identified 44 genetic variants including eight coding SNPs in RRM1 and 15 SNPs including one coding SNP in RRM2. RRM1 and RRM2 mRNA expression levels were significantly correlated with each other in both CEU and YRI lymphoblast cell lines, and in leukemic blasts from acute myeloid leukemia (AML) patients (AML97, n = 89; AML02, n = 187). Additionally, RRM1 expression was higher among patient features indicative of a high relapse hazard. We evaluated SNPs within the RRM1 and RRM2 genes in the HapMap lymphoblast cell lines from CEU and YRI panels for association with expression and cytarabine chemosensitivity. SNPs of potential significance were further evaluated in AML patients. RRM1 SNPs rs1042919 (which occurs in linkage disequilbrium with multiple other SNPs) and promoter SNP rs1561876 were associated with intracellular 1-β-D-arabinofuranosyl-CTP levels, response after remission induction therapy, risk of relapse and overall survival in AML patients receiving cytarabine and cladribine.

CONCLUSION

These results suggest that SNPs within ribonucleotide reductase might be helpful predictive markers of response to nucleoside analogs and should be further validated in larger cohorts.

NF-κB and CREB are required for angiotensin II type 1 receptor upregulation in neurons

Nuclear factor kappa B (NF-κB) and the Ets like gene-1 (Elk-1) are two transcription factors that have been previously established to contribute to the Angiotensin II mediated upregulation of Angiotensin II type 1 receptor (AT1R) in neurons. The cAMP response element binding protein (CREB) is another transcription factor that has also been implicated in AT1R gene transcription. The goal of the current study was to determine if NF-κB and CREB association was required for AT1R upregulation. We hypothesized that the transcription of the AT1R gene occurs via an orchestration of transcription factor interactions including NF-κB, CREB, and Elk-1. The synergistic role of CREB and NFκB in promoting AT1R gene expression was determined using siRNA-mediated silencing of CREB. Electrophorectic Mobility Shift Assay studies employing CREB and NF-κB demonstrated increased protein - DNA binding as a result of Ang II stimulation which was blunted by siRNA silencing of CREB. Upstream inhibition of p38 mitogen activated protein kinase (p38 MAPK) with SB203580 or inhibition of the calmodulin kinase (CAMK) pathway using KN-62 blunted changes in CREB and NF-κB expression. These findings suggest that Ang II may activate multiple signaling pathways involving p38 MAPK leading to the activation of NF-κB and CREB, which feed back to upregulate the AT1R gene. This study provides insight into the molecular mechanisms involving multiple transcription factor activation in a coordinated fashion which may be partially responsible for sympathoexcitation in clinical conditions associated with increased activation of the renin angiotensin system.

Exon 8-9 mutations of DNA polymerase β in ovarian carcinoma patients from Haldia, India

BACKGROUND

Ovarian cancer is the number one killer among all the gynecological cancers. We undertook association study to identify potential alterations in the genomic DNA of a DNA repair gene, DNA polymerase beta (polβ), involved in base excision repair (BER), in ovarian carcinomas of patients from Haldia, India. Mutations, splice variants have been reported earlier in different tumors other than ovarian tumors.

AIM

In this study we explored the possibility of association of any mutation of pol beta (Exon 8) with prognosis in 152 ovarian cancer samples.

RESULTS

Alteration in the exon 8 region (Exon 8:468, AgC; 15.1%) was noted among fifty seven polymorphism positive samples. Alteration in the intervening sequence 8 (IVS8, -25, AgC; 3.9%) was also noted. All alterations are heterozygous in nature.

CONCLUSIONS

We found no significant association among the samples from serous type, stage IV, and the polβ mutations (P ≤ 0.01). Only a slight tendency of association was evident between IVS8, -25, A to C; and stage III. Further analysis with a larger number of samples is needed.

Pathway-based pharmacogenomics of gemcitabine pharmacokinetics in patients with solid tumors

AIM

The aim of this study was to evaluate the association of gemcitabine pathway SNPs with detailed pharmacokinetic measures obtained from solid tumor patients receiving gemcitabine-based therapy.

MATERIALS & METHODS

SNPs within nine gemcitabine pathway genes, namely CDA, CMPK, DCK, DCTD, NT5C2, NT5C3, SLC28A1, SLC28A3 and SLC29A1 were analyzed for association with gemcitabine pharmacokinetics.

RESULTS

Significant association of gemcitabine clearance with SNPs in NT5C2 was identified. Clearance of 2´,2´-difluorodeoxyuridine, a gemcitabine metabolite was significantly predicted by CDA, SLC29A1 and NT5C2 SNPs. This study reports an association of formation clearance of 2´,2´-difluoro-2´-deoxycytidine triphosphate, an active form of gemcitabine with SNPs within uptake transporters SLC28A1, SLC28A3 and SLC29A1.

CONCLUSION

Genetic variation in gemcitabine pathway genes is associated with its pharmacokinetics and hence could influence gemcitabine response. Our study identified pharmacogenetic markers that could be further tested in larger patient cohorts and could open up opportunities to individualize therapy in solid tumor patients.

Clinical significance of CD33 nonsynonymous single-nucleotide polymorphisms in pediatric patients with acute myeloid leukemia treated with gemtuzumab-ozogamicin-containing chemotherapy

PURPOSE

The purpose of this study was to evaluate clinical implications of CD33 single-nucleotide polymorphisms (SNP) in pediatric patients with acute myeloid leukemia (AML) treated with gemtuzumab-ozogamicin (GO)-based therapy.

EXPERIMENTAL DESIGN

We genotyped four CD33 SNPs: rs35112940 (G>A; Arg304Gly), rs12459419 (C>T; Ala14Val), rs2455069 (A>G; Arg69Gly), and rs1803254 (G>C; 3'UTR) in pediatric patients undergoing induction chemotherapy containing GO (COG-AAML03P1 trial; n = 242) or not containing GO (St. Jude AML02 trial; n = 172).

RESULTS

CD33 SNPs were correlated significantly with clinical characteristics and treatment outcome. The coding SNPs, rs35112940 and rs12459419, were significantly associated with clinical endpoints in COG-AAML03P1 but not in the St. Jude AML02 trial. Specifically, among white patients in COG-AAML03P1, the 3-year overall survival (OS) rate from remission was 84% ± 8% for those homozygous (GG) for rs35112940 versus 68% ± 15% for the other genotypes (P = 0.018); these patients also had a lower relapse risk and superior disease-free survival. Likewise, patients homozygous for variant allele (TT) for rs12459419 were more likely to have favorable risk disease than CC and CT genotypes (52% vs. 31%, P = 0.034) and significantly lower diagnostic blast CD33 expression than other genotypes (P < 0.001).

CONCLUSION

Our data suggest that genetic variations in CD33 could impact clinical outcome of GO-based therapy in pediatric AMLs.

Abstract 1882: Gemcitabine pathway SNPs are associated with its PK parameters in patients with solid tumors

Gemcitabine (2′, 2′-difluoro 2′-deoxycytidine, dFdC) is a cytotoxic pyrimidine antimetabolite used as first-line chemotherapeutic agent for the treatment of a wide range of solid tumors and hematologic malignancies. It is as a pro-drug that undergoes cellular uptake through transporters like human equilibrative nucleoside transporter (hENT1/SLC29A1) and human concentrative nucleoside transporters (hCNT1/SLC28A1 and hCNT3/SLC28A3) followed by extensive intracellular phosphorylation by kinases like deoxycytidine kinase (DCK) and cytidine monophosphate kinase (CMPK) to its active diphosphorylated (dFdCDP) and triphosphorylated (dFdCTP) forms. Gemcitabine is primarily inactivated via deamination to its less potent metabolite 2′, 2′-difluorodeoxyuridine (dFdU) by cytidine deaminase (CDA). High inter-patient variability in response to gemcitabine treatment has been a major concern in gemcitabine chemotherapy. However, association of pharmacogenomics with gemcitabine pharmacokinetics (PK) has not been extensively studied so far. In the present study, therefore, we investigated association between single nucleotide polymorphisms (SNPs) within genes involved in gemcitabine transport/metabolic pathway and pharmacokinetic parameter estimates for gemcitabine and metabolites in patients diagnosed with solid tumors. Pharmacokinetic blood sampling (n=40) was as follows: pre-infusion, 5, 15, 30, 45 min, and 1, 1.25, 1.5, 2, 6, 24, 48 and 72 hours after the end of gemcitabine infusion. Gemcitabine and dFdU concentrations in plasma and intracellular dFdCTP levels in PBMCs were measured using HPLC-UV and LC MS/MS. A total of 86 SNPs in 14 genes viz. CDA, CMPK, CTPS, DCK, DCTD, NME1, NME2, NME3, NME4, NT5C2, NT5C3, SLC28A1, SLC28A3, and SLC29A1 were genotyped using Sequenom-based assays. Pharmacogenomic association was evaluated using Wilcoxon rank-sum test and Kruskal-Wallis one-way analysis of variance by ranks (p≤0.05). SNPs in 5′ nucleotidase genes- rs1163075, rs1926029, rs11598702 and rs1712517 in NT5C2 and rs3750117 in NT5C3 were associated with gemcitabine elimination clearance. SNPs in CDA- rs1048977 and rs4655226 were associated with dFdU clearance. SNPs in CTPS- rs4430318, rs61780437 and rs1044457 were strongly associated with higher dFdCTP formation clearance. Additionally, CDA, DCTD, SLC28A1, SLC28A3 and SLC29A1 SNPs were also associated with dFdCTP formation clearance. The results from our study indicate pharmacogenomic association between gemcitabine pharmacokinetic pathway SNPs and PK parameters. Presence of these SNPs could impact outcomes for patients receiving gemcitabine therapy.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1882. doi:1538-7445.AM2012-1882

Abstract LB-228: Association of XRCC1 SNPs with clinical response in AML patients

DNA repair system is critical in maintaining genome stability and integrity in response to various exogenous and endogenous stress factors. It is a multistep processes involving several enzymes including XRCC1 (X-ray repair cross-complementing group1) protein which plays a vital role in DNA repair activities and therefore is important for maintenance of genetic stability. The current study involves investigation of single nucleotide polymorphisms (SNPs) in the XRCC1 gene and their association with clinical response in pediatric acute myeloid leukemia (AML) patients treated with cytarabine (ara-C) based anti-leukemic chemotherapy in the St. Jude AML02 clinical trial. The St. Jude AML02 trial enrolled 232 AML patients less than 22 years of age, randomized to receive induction I therapy containing high-dose cytarabine or low-dose cytarabine plus daunorubicin and etoposide. A total of eighteen XRCC1 SNPs were genotyped using MALDI-TOF based Sequenom assay and screened for association with 3 endpoints, namely: in vitro ara-C LC50 determined in leukemic cells obtained at diagnosis (which was measured by treating leukemic cells in vitro with varying concentrations of ara-C), event free survival (EFS) and overall survival (OS). Jung statistic was used to determine association of the number of minor alleles with EFS and OS. Association of genotypes with EFS and OS was measured using Cox regression models while considering previously identified prognostically important variables. Our results showed significant association of 4 XRCC1 SNPs with survival and ara-C LC50 in pediatric AML patients. Three of these were present in the coding region, while one was a regulatory SNP located in the promoter region of the XRCC1 gene. XRCC1 SNPs have also been shown to be associated with cancer susceptibility and survival in previous studies. Our results now demonstrate clinical significance of XRCC1 SNPs in pediatric AML and suggest a role of these SNPs as prognostic factors in AML chemotherapy. These results might open up opportunities for tailored chemotherapy based on genomic markers to improve therapeutic outcome.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr LB-228. doi:1538-7445.AM2012-LB-228

Functional characterization of folate transport proteins in Staten's Seruminstitut rabbit corneal epithelial cell line

PURPOSE

The overall objective of this study was to investigate and characterize the expression of folate transport proteins in Staten's Seruminstitut rabbit corneal (SIRC) epithelial cell line.

METHODS

[(3)H]Folic acid uptake was studied with respect to time, pH, temperature, sodium, and chloride ion dependency. Inhibition studies were conducted with structural analogs, vitamins, and metabolic inhibitors. [(3)H]Folic acid uptake was also determined with varying concentrations of cold folic acid. Uptake kinetics was studied in the presence of various modulators of intracellular regulatory pathways, protein kinases A and C (PKA and PKC), protein tyrosine kinase (PTK), and calcium-calmodulin modulators. Ex vivo corneal permeability studies were carried out with [(3)H]folic acid in the presence and absence of 1 mM cold folic acid.

RESULTS

Linear increase in [(3)H]folic acid uptake was observed over 30 min. The process followed saturation kinetics with apparent K(m) of 14.2 ± 0.2 nM, V(max) of (1.5 ± 0.1)*10(-5) micro.moles/min/mg protein, and K(d) of (2.1 ± 0.2)*10(-6) min(-1). The uptake process was found to be dependent on pH, sodium ions, chloride ions, temperature, and energy. Uptake was inhibited in the presence of structural analogs (cold folic acid, methyltetrahydro folate, and methotrexate), but structurally unrelated vitamins did not show any effect. Membrane transport inhibitors SITS, DIDS, probenecid and endocytic inhibitor, colchicine significantly inhibited the [(3)H]folic acid uptake indicating the involvement of receptor/transporter mediated process. PKA, PTK, and Ca(2+)/calmodulin pathways significantly regulate the process. RT-PCR and Western blot analysis confirmed the presence of folate receptor-α (FR-alpha) and proton-coupled folate transporter (PCFT). Permeability of [(3)H]folic acid across the rabbit cornea was (1.48 ± 0.13)*10(-05) cm/sec, and in the presence of cold folic acid it was (1.08 ± 0.10)*10(-05) cm/sec.

CONCLUSIONS

This work demonstrated the functional and molecular presence of FR-alpha and PCFT in SIRC epithelial cell line.

Genetic variants in cytosolic 5'-nucleotidase II are associated with its expression and cytarabine sensitivity in HapMap cell lines and in patients with acute myeloid leukemia

Cytosolic 5'-nucleotidase II (NT5C2) is involved in the development of 1-β-d-arabinofuranosylcytosine (ara-C) resistance and has been associated with clinical outcome in patients receiving ara-C-based chemotherapy. NT5C2 inactivates ara-C by dephosphorylating ara-C monophosphate to ara-C. In this study, we sequenced NT5C2 in genomic DNA samples from International HapMap project panels with European [Centre d'Etude du Polymorphisme Humain (CEU); n = 90] or African [Yoruba people in Ibadan, Nigeria (YRI); n = 90] ancestry. We identified 41 genetic variants [one insertion-deletion and 40 single nucleotide polymorphisms (SNPs)], including three nonsynonymous SNPs (Y3A, K47R, and Q136R). Twenty-five SNPs were novel and 16 overlapped with the HapMap data. Subjects with African ancestry had NT5C2 mRNA expression levels that was significantly higher than those with European ancestry (p = 0.005). Furthermore, there was a correlation between NT5C2 mRNA expression and ara-C sensitivity in CEU but not in YRI cell lines. None of the nonsynonymous SNPs demonstrated any effect on NT5C2 activity. The genotypes of several SNPs were significantly associated with NT5C2 mRNA expression and/or ara-C sensitivity in CEU cell lines, but very few were significant in YRI cell lines. Of most interest, SNPs (linkage disequilibrium group CEU.12) in the 5'-untranslated region were associated with NT5C2 expression and ara-C sensitivity in HapMap cell lines and with NT5C2 mRNA expression and ara-C sensitivity in diagnostic leukemic blasts from pediatric patients with acute myeloid leukemia. Functional genomics analysis demonstrated that the promoter SNP rs11191612 was associated with altered luciferase activation in reporter assays and altered DNA-protein binding in gel shift assays. These results suggest that genetic variations in NT5C2 influence its expression and, potentially, cellular responses to nucleoside analogs.

Effect of high temperature and the presence of stone-wales defects on the mechanical behavior of a single wall carbon nanotube under tension and compression

On the basis of molecular dynamics simulation, a zigzag (7, 0) SWCNT is examined under axial tension and compression to observe its mechanical behavior and fracture pattern in the absence and presence of Stone-Wales (SW) defects coupled with the variation of temperature. A defect-free tube is subjected to tensile or compressive stresses at different temperatures. Then SW defects are introduced into it and stress is applied with the increase of temperature. The defective and defect-free tubes show different fracture patterns with increasing temperature showing significant changes in their mechanical properties. Compression of the tube also reveals interesting changes in its buckling behavior with variation of temperature and inclusion of defects.

Angiotensin II-induced upregulation of AT(1) receptor expression: sequential activation of NF-kappaB and Elk-1 in neurons

It has been clearly established that increased circulating angiotensin II (ANG II) with concurrent upregulation of brain and peripheral ANG II type 1 receptors (AT(1)R) are important mediators in the pathophysiology of several diseases characterized by sympatho-excitation. In an effort to further understand the regulation of AT(1)R expression in neurons, we determined the role of sequential activation of the transcription factors nuclear factor-kappaB (NF-kappaB) and Ets-like protein 1 (Elk-1) in AT(1)R upregulation. We used CATH.a neurons as our neuronal cell model. Cells were treated with ANG II (100 nM) over a preset time course. Following ANG II activation, there was a temporal increase in the p65 subunit of NF-kappaB that was observed at 30 min, peaked at 1 h, and was sustained up to 24 h. There was a concomitant decrease of IkappaB and increased IkappaK expression. We also observed an increase in AT(1)R expression which followed the temporal increase of NF-kappaB. The activation of NF-kappaB was blocked by using the inhibitors parthenolide or p65 small interfering RNA (siRNA) which both led to a decrease in AT(1)R expression. The expression of Elk-1 was upregulated over a time period following ANG II activation and was decreased following NF-kappaB inhibition. p65-DNA binding was assessed using electrophoretic mobility shift assay, and it was shown that there was a time-dependent increased binding that was inhibited by means of parthenolide pretreatment or siRNA-mediated p65 gene silencing. Therefore, our results suggest a combined role for the transcription factors NF-kappaB and Elk-1 in the upregulation of AT(1)R in the CATH.a cell neuronal model. These data imply a positive feedback mechanism that may impact neuronal discharge sensitivity in response to ANG II.

Insulin-like growth factor-1 induces phosphorylation of PI3K-Akt/PKB to potentiate proliferation of smooth muscle cells in human saphenous vein

Coronary revascularization by coronary artery bypass grafting (CABG) is recommended in patients with recurrent myocardial ischemia. However, the long-term results of CABG using saphenous vein (SV) graft, compared to internal mammary artery (IMA) graft, have not been satisfactory. The SV graft failure is due to the development of intimal hyperplasia, a process characterized by abnormal migration and proliferation of smooth muscle cells (SMCs) in the intimal layer of the vein graft. Insulin growth factor 1 (IGF-1) is a major mitogenic growth factor released at the site of the shear stress-induced graft injury. This study, for the first time, compares the extent of IGF-1-PI3K-Akt activation in isolated human bypass graft conduits. Human SV and IMA vessels were collected and SMCs isolated and cultured. In cultured SMCs, effect of IGF-1 was examined on total and phosphorylated PI3K, Akt and IGF-1R by Western blot analysis. Cell proliferation was measured using BrdU ELISA. There was no significant difference in the basal expression of phosphorylated PI3K, Akt and IGF-1R in SV and IMA SMCs from human bypass conduits. However, we observed an upregulation of IGF-1 receptors in the SV SMCs in response to IGF-1 stimulation with no effect in IMA SMCs. Furthermore, the immunoblotting and cellular activation of signaling ELISA (CASE) assay demonstrated a significantly higher activity of both PI3K and Akt in IGF-1-stimulated SV SMCs than IMA. This was inhibited by an IGF-1R blocking antibody. IGF-1 induced proliferation in both SV and IMA SMCs was inhibited by a PI3K inhibitor, wortmannin. These data demonstrate differential activity of IGF-1-induced PI3K-Akt activation, which was quantitatively and temporally greater in SV SMCs than in the IMA. This, at least in part, could explain the greater propensity of the SV conduits than the IMA to undergo intimal hyperplasia following CABG.

Viral obesity: fact or fiction?

The aetiology of obesity is multifactorial. An understanding of the contributions of various causal factors is essential for the proper management of obesity. Although it is primarily thought of as a condition brought on by lifestyle choices, recent evidence shows there is a link between obesity and viral infections. Numerous animal models have documented an increased body weight and a number of physiologic changes, including increased insulin sensitivity, increased glucose uptake and decreased leptin secretion that contribute to an increase in body fat in adenovirus-36 infection. Other viral agents associated with increasing obesity in animals included canine distemper virus, rous-associated virus 7, scrapie, Borna disease virus, SMAM-1 and other adenoviruses. This review attempted to determine if viral infection is a possible cause of obesity. Also, this paper discussed mechanisms by which viruses might produce obesity. Based on the evidence presented in this paper, it can be concluded that a link between obesity and viral infections cannot be ruled out. Further epidemiologic studies are needed to establish a causal link between the two, and determine if these results can be used in future management and prevention of obesity.

Three-photon-induced four-photon absorption and nonlinear refraction in ZnO quantum dots

Three-photon-induced four-photon absorption via excited-state absorption and self-defocusing nonlinear refraction are reported for the first time, to our knowledge, in ZnO quantum dots with average sizes of 2.0+/-0.1 nm with 1064 nm radiation from a Q-switched Nd:YAG laser at a peak intensity of 2.5 GW/cm(2). By employing the three-level two-step model, the experimental results can be explained quite satisfactorily.

Regulation of cell cycle entry by PTEN in smooth muscle cell proliferation of human coronary artery bypass conduits

Proliferation of smooth muscle cells (SMCs) is the key event in the pathogenesis of intimal hyperplasia (IH) leading to coronary artery bypass graft (CABG) occlusion. The saphenous vein (SV) conduits are often affected by IH, while the internal mammary artery (IMA) conduits remain remarkably patent. SMC proliferation is mediated by the cell cycle, under the control of cyclin-dependent kinases (cdks), cdk-inhibitors and the retinoblastoma protein (Rb). Early passage of the SMCs through the cell cycle involves crossing the non-reversible G(1) checkpoint, the restriction (R) point. In this study, we investigated the effect of mitogenic insulin-like growth factor (IGF)-1 stimulation on the R-point and its relationship with the phosphorylation of Rb protein and the cdk inhibitors p21 and p27 in SV and IMA SMCs. We observed no change in the R-point following IGF-1 activation in either SV or IMA SMCs. However, Rb-phosphorylation occurred much earlier and was quantitatively greater in SV SMCs than IMA. Overexpression of phosphatase and tensin homologue deleted on chromosome 10 (PTEN) in SV SMCs followed by IGF-1 activation significantly decreased the expression of cyclin E and pRb and induced p27 expression in SV SMCs, while, pRb levels were markedly decreased and p27 levels were significantly increased in IMA SMCs. Silencing the PTEN gene by siRNA transfection of IMA SMCs significantly induced the expression of pRb and inhibited p27 expression, while, the expression levels of cyclin E, pRb, p21 and p27 were unaffected by the silencing of PTEN in SV SMCs. These results demonstrate that the PTEN plays a critical role in regulating cell cycle entry. Therefore, overexpression of PTEN possibly by means of gene therapy could be a viable option in regulating the cell cycle in SV SMCs in the treatment of vein graft disease.

Conformational analysis of cyclo (L-cystine)

Conformational analysis of cyclo(L-cystine) shows that the diketopiperazine ring has to exist only in the boat form. With this geometry, the molecule can adopt two distinct forms differing mainly in the chirality of the disulphide bridge. In both the P- and M-models, corresponding to dihedral angles of nearly +90 degrees and -90 degrees respectively about the S-S- bond, the molecule displays an approximate two-fold symmetry. According to our semi-empirical energy calculations, the minimum energy of the M-model is --9.2 kcal/mol, only 0.3 kcal/mol lower than that of the P-model. Because the difference between the two minima is so small, neither form is clearly superior to the other. However, the number of low energy conformations of the M-model in the allowed conformational space is significantly larger than that of the P-model by a ratio of 3 to 1, and therefore the former is likely to be thermodynamically favoured.

Temporal PTEN inactivation causes proliferation of saphenous vein smooth muscle cells of human CABG conduits

Internal mammary artery (IMA) coronary artery bypass grafts (CABG) are remarkably resistant to intimal hyperplasia (IH) as compared to saphenous vein (SV) grafts following aorto-coronary anastomosis. The reason behind this puzzling difference still remains an enigma. In this study, we examined the effects of IGF-1 stimulation on the PI3K-AKT/PKB pathway mediating proliferation of smooth muscle cells (SMCs) of IMA and SV origin and the specific contribution of phosphatase and tensin homologue (PTEN) in regulating the IGF-1-PI3K-AKT/PKB axis under these conditions. Mitogenic activation with IGF-1, time-dependently stimulated the phosphorylation of PI3K and AKT/PKB in the SV SMCs to a much greater extent than the IMA. Conversely, PTEN was found to be significantly more active in IMA SMCs. Transient overexpression of PTEN in SMCs of SV and IMA inhibited AKT/PKB activity and upstream of AKT/PKB, caused a reduction of IGF-1 receptors. Downstream, PTEN overexpression in SV SMCs induced the transactivation of tumour suppressor protein p53 by down-regulating the expression of its inhibitor MDM2. However, PTEN overexpression had no significant effect on MDM2 and p53 expression in IMA SMCs. PTEN overexpression inhibited IGF-1-induced SMC proliferation in both SV and IMA. PTEN suppression, induced by siRNA transfection of IMA SMCs diminished the negative regulation of PI3K-PKB signalling leading to greater proliferative response induced by IGF-1 stimulation. Thus, we show for the first time that early inactivation of PTEN in SV SMCs leads to temporally increased activity of the pro-hyperplasia PI3K-AKT/PKB pathway leading to IH-induced vein graft occlusion. Therefore, modulation of the PI3K-AKT/PKB pathway via PTEN might be a novel and effective strategy in combating SV graft failure following CABG.

Angiotensin II and IGF-1 regulate connexin43 expression via ERK and p38 signaling pathways in vascular smooth muscle cells of coronary artery bypass conduits

BACKGROUND

Changes in connexin expression have been found in vascular smooth muscle cells (VSMCs) during the progression of atherosclerotic lesion and intimal hyperplasia. It is our hypothesis that increased connexin43 expression following stimulation of VSMCs with Ang II and IGF-1 contributes to more proliferation in saphenous vein (SV) than in the internal mammary artery (IMA).

MATERIALS AND METHOD

Using immunohistochemistry, Western blot, and reverse-transcription polymerase chain reaction, we assessed the effect of Ang II and IGF-1 stimulation on connexin43 expression and the signaling pathways involved in VSMCs of SV and IMA.

RESULTS

Immunostaining demonstrated strong expression of connexin43 in SV compared with IMA after stimulation with Ang II and IGF-1. Ang II up-regulated the expression of connexin43 in VSMCs of SV in a dose- and time-dependent manner. This was inhibited by p38 and ERK MAP kinase inhibitors, SB203580 and PD98059, respectively. In the VSMCs of IMA, the connexin43 expression was markedly low and maintained at a reduced level even after 3 h stimulation. IGF-1 dose-dependently induced mRNA expression of connexin43 in the VSMCs of SV, which was blocked by PD98059. However, in VSMCs of IMA there was no significant effect of IGF-1 on the connexin43 mRNA expression.

CONCLUSION

These data suggest that connexin43 expression can be influenced by Ang II and IGF-1 through ERK and p38 pathways and may contribute to the pathogenesis of vein graft disease following coronary artery bypass grafting.

EDXRF analysis of municipal solid waste using 109Cd source

Elemental compositions of municipal solid waste (MSW) samples have been analyzed using the non-destructive energy dispersive X-ray fluorescence (EDXRF) technique. The samples were collected from three different dumping sites of urban and suburban areas of the city of Kolkata, West Bengal, India. The EDXRF spectrometer consisted of a (109)Cd radioactive source and a Si (Li) detector. To check the reliability of the system, NIST Standard Reference Material-1648 UPM had been analyzed and it was found that within the experimental errors, our results agree quite well with the certified and non-certified values. The elemental compositions of all the three MSW samples were subsequently estimated using the same procedure. The matrix effects were estimated following the emission-transmission method. It was observed that except Fe, all the elements from Ti to Pb show concentration levels higher by a factor of 2-7 than the ecological screening values where as in the case of Fe, this factor varies from 100 to 200.

Gene therapy of fibroproliferative vasculopathies: current ideas in molecular mechanisms and biomedical technology

Intimal hyperplasia occurs primarily as a part of the pathogenesis of coronary artery disease or secondary to therapeutic intervention in relieving vascular occlusion. Intimal hyperplasia involving vascular smooth muscle cells is found in atherosclerosis, post-balloon angioplasty restenosis, in-stent restenosis and vein graft disease, predominantly involving the use of saphenous vein conduits in coronary artery bypass grafting procedures. One potentially exciting area is that of gene therapy. Gene and protein expression patterns at the site of vasculoproliferative lesions have been widely studied and several target areas have been identified on the basis of whether the gene has an antiproliferative, proapoptotic, matrix degrading or endothelial protective action. Blood vessels are easily accessible for the delivery of the gene product, and experimental studies using animal models have used catheter-delivered gene products at the site of vascular injury. Currently, the application of antisense technology and adenoviral vector-mediated delivery has shown significant promise, albeit in in vitro or animal model settings. In this review, we discuss the current knowledge in the application of gene therapy in fibroproliferative vasculopathies. We examine some of the cellular mechanisms and intermediaries which could be potential candidates for gene targeting. We also present some of the advances in biomedical technology that might provide useful vehicles for pinpoint delivery of the gene product. Could the future of restenosis treatment be in gene therapy or is it misplaced enthusiasm?

Cellular, molecular and immunological mechanisms in the pathophysiology of vein graft intimal hyperplasia

Coronary artery disease, leading to myocardial infarction and ischaemia, affects millions of persons and is one of the leading causes of morbidity and mortality worldwide. Invasive techniques such as coronary artery bypass grafting are used to alleviate the sequelae of arterial occlusion. Unfortunately, restenosis or occlusion of the grafted conduit occurs over a time frame of months to years with a gradual reduction in patency, especially in vein grafts. The events leading to intimal hyperplasia (IH) formation involve numerous cellular and molecular components. Various cellular elements of the vessel wall are involved as are leucocyte-endothelial interactions that trigger the coagulation cascade leading to localized thrombus formation. Subsequent phenotypic modification of the medial smooth muscle cells and their intimal migration is the basis of the lesion formation that is thought to be propagated by an immune-mediated reaction. Despite intense scrutiny, the pathophysiology of IH remains an enigma. Although several growth factors, cytokines and numerous other biomolecules have been implicated and their relationship to prohyperplasia pathways such as the phosphatidyl-inositol 3-kinase (PI3K)-Akt pathway has been established, many pieces of the puzzle are still missing. An in-depth understanding of early vein graft adaptation and progression is necessary to improve the long-term prognosis and develop more effective therapeutic measures. In this review, we have critically evaluated and summarized the literature to elucidate and interlink the numerous established and emerging factors that play a key role in the development of IH leading to vein graft restenosis.

In stent restenosis: bane of the stent era

The long term outcome of stent implantation is affected by a process called in stent restenosis (ISR). Multiple contributory factors have been identified, but clear understanding of the overall underlying mechanism remains an enigma. ISR progresses through several different phases and involves numerous cellular and molecular constituents. Platelets and macrophages play a central role via vascular smooth muscle cell migration and proliferation in the intima to produce neointimal hyperplasia, which is pathognomic of ISR. Increased extracellular matrix formation appears to form the bulk of the neointimal hyperplasia tissue. Emerging evidence of the role of inflammatory cytokines and suppressors of cytokine signalling make this an exciting and novel field of antirestenosis research. Activation of Akt pathway triggered by mechanical stretch may also be a contributory factor to ISR formation. Prevention of ISR appears to be a multipronged attack as no therapeutic "magic bullet" exists to block all the processes in one go.

Cells, cytokines and cellular immunity in the pathogenesis of fibroproliferative vasculopathies

Atherosclerosis and restenosis are the result of vascular injury followed by an inflammatory and fibroproliferative response that involves a large number of growth factors, cytokines, and cellular elements. Platelet activation and leukocyte recruitment into the arterial intima play a crucial role, initiating a whole spectrum of reactions leading to vascular smooth muscle cell hyperplasia and intimal migration. The roles of macrophages and lymphocytes and mast cells as mediators of inflammation and immune response is discussed, as are the roles of growth factors and cytokines. New light on the 'old' problems will help us to devise newer and better therapeutic strategies to combat these clinical entities.

A comparison of stent-induced stenosis in coronary and peripheral arteries

BACKGROUND AND OBJECTIVES

Restenosis is a complication of interventional procedures such as angioplasty and stenting, often limiting the success of these procedures. Knowledge regarding the relative behaviour of different arteries after these procedures is limited, despite the extensive use of different vascular models. Although the results from studies using different vessels are analysed to predict the behaviour of coronary arteries and other vasculature, direct controlled comparisons between different arteries are necessary for a better understanding of the differential response to restenosis.

METHODS

This study examines the response to stenting in coronary and internal iliac arteries as characterised by intimal hyperplasia and restenosis. In a swine model of in-stent stenosis, coronary arteries exhibited higher levels of intimal hyperplasia and per cent stenosis than internal iliac arteries.

RESULTS

After normalisation for injury score, coronary arteries were found to undergo 47% more intimal hyperplasia (p<0.05), whereas per cent stenosis normalised for injury score tended to be higher (p = 0.01). Other measurements reflecting post-stenting intimal hyperplasia (maximal intimal thickness, medial area) did not exhibit significant differences between the artery groups.

CONCLUSIONS

These results show that coronary vessels are more prone to develop significant intimal hyperplasia and subsequent restenosis than internal iliac vessels. A better insight into how different arteries and arterial components behave is important in understanding and developing newer and better therapeutic measures for restenosis.

Comparing 2-year outcomes of anterior cruciate ligament reconstruction using either patella-tendon or semitendinosus-tendon autografts: a non-randomised prospective study

PURPOSE

To compare the results of anterior cruciate ligament (ACL) reconstructions using either a patella-tendon autograft or a semitendinosus-tendon autograft.

METHODS

Based on surgeon experience and preference, 68 patients underwent ACL reconstruction using either a quadruple-strand semitendinosus autograft (n = 34) or a central one-third bone-patella tendon-bone autograft (n = 34). Each patient was assessed preoperatively and postoperatively at 3, 6, and 24 months using the International Knee Documentation Committee (IKDC) knee score, Biodex muscle strength and endurance testing, and the KT1000 instrumented arthrometer test of knee laxity to anterior translation. All assessments at the 2-year follow-up were performed by the same physician and physiotherapist.

RESULTS

While ACL reconstruction improved knee stability and IKDC knee scores significantly, there was no statistically significant difference between semitendinosus- and patella-tendon autograft reconstructions in terms of long-term knee score or laxity to anterior translation. Semitendinosus graft reconstruction was associated with less donor-site morbidity and hamstring weakness. Meniscectomy was associated with poorer long-term knee scores.

CONCLUSION

ACL reconstruction is associated with a significantly better IKDC knee score and laxity measurement at 2-year follow-up. However, we were unable to demonstrate a significantly better long-term outcome in knee score or laxity to anterior translation with either a patella-tendon autograft or a semitendinosus-tendon autograft.

Assessment of blood-induced cartilage damage in rabbit knees using scanning electron microscopy

PURPOSE

To investigate the harmful effects of a single episode of intra-articular bleeding on articular cartilage of rabbit knees using scanning electron microscopy.

METHODS

Autologous blood was injected into the right knee joints of 18 New Zealand white rabbits. Surface and cellular damages were examined by the scanning electron microscope (n=9) and light microscope (n=34), respectively. The injected right knees were then compared with the corresponding control left knees at one, 3, and 6 weeks after the blood injection.

RESULTS

The articular surface of the injected knees turned uniformly rough with multiple pits after one week. Maximal changes with elevations and depressions were observed at 3 weeks. These changes reversed at 6 weeks with the irregularities smoothing out. A similar pattern of transient cartilage damage was noted histologically.

CONCLUSION

Both scanning electron microscopic and light microscopic findings suggest that a single episode of intra-articular bleeding leads to articular cartilage damage but this appears to be reversible. Our findings of transient damage to the articular cartilage suggest that there is no need for intra-articular evacuation and washout following an acute episode of haemarthrosis.

"Vulnerable plaques" — ticking of the time bomb

Atherosclerosis and its sequelae are one of the leading causes of morbidity and mortality, especially in the developed nations. Over the years, treatment protocols have changed with the changing understanding of the disease process. Inflammatory mechanisms have emerged as key players in the formation of the atherosclerotic plaque. For the majority of its life span, the plaque develops silently and only some exhibit overt clinical manifestations. The purpose of this review is to examine the inherent properties of some of these "vulnerable" or symptomatic plaques. Rupture of the plaque is related to the thickness of the fibrous cap overlying the necrotic lipid core. A thin cap is more likely to lead to rupture. Multiple factors broadly grouped as the "determinants of vulnerability" are responsible for directly or indirectly influencing the plaque dynamics. Apoptosis is considered an important underlying mechanism that contributes to plaque instability. Inflammatory reactions within the plaque trigger apoptosis by cell–cell contact and intra cellular death signaling. Once started, the apoptotic process affects all of the components that make up the plaque, including vascular smooth muscle cells, endothelial cells, and macrophages. Extensive research has identified many of the key cellular and molecular regulators that play a part in apoptosis within the atherosclerotic lesion. This information will help us to gain a better understanding of the underlying mechanisms at the cellular and molecular level and enable us to formulate better therapeutic strategies to combat this disease.Key words: apoptosis, atherosclerosis, inflammation, plaque stability, vulnerable plaques.

Arsenic concentrations in rice, vegetables, and fish in Bangladesh: a preliminary study

Arsenic contaminating groundwater in Bangladesh is one of the largest environmental health hazards in the world. Because of the potential risk to human health through consumption of agricultural produce grown in fields irrigated with arsenic contaminated water, we have determined the level of contamination in 100 samples of crop, vegetables and fresh water fish collected from three different regions in Bangladesh. Arsenic concentrations were determined by hydride generation atomic absorption spectrophotometry. All 11 samples of water and 18 samples of soil exceeded the expected limits of arsenic. No samples of rice grain (Oryza sativa L.) had arsenic concentrations more than the recommended limit of 1.0 mg/kg. However, rice plants, especially the roots had a significantly higher concentration of arsenic (2.4 mg/kg) compared to stem (0.73 mg/kg) and rice grains (0.14 mg/kg). Arsenic contents of vegetables varied; those exceeding the food safety limits included Kachu sak (Colocasia antiquorum) (0.09-3.99 mg/kg, n=9), potatoes (Solanum tuberisum) (0.07-1.36 mg/kg, n=5), and Kalmi sak (Ipomoea reptoms) (0.1-1.53 mg/kg, n=6). Lata fish (Ophicephalus punctatus) did not contain unacceptable levels of arsenic. These results indicate that arsenic contaminates some food items in Bangladesh. Further studies with larger samples are needed to demonstrate the extent of arsenic contamination of food in Bangladesh.

Morbidity following anterior cruciate ligament reconstruction using hamstring autograft

INTRODUCTION

As anterior cruciate ligament (ACL) reconstruction becomes more frequently performed, the expectation of earlier return to activities becomes higher; hence graft selection becomes more important. The use of hamstring tendon autograft is perceived to have less postoperative morbidities. We evaluate the early postoperative complications in this prospective study.

MATERIALS AND METHODS

Seventy-six patients operated by the same surgeon were assessed preoperatively, and 3 and 6 months after surgery. The hamstring and quadriceps strength were measured with Biodex machine and the side-to-side laxity measured using KT-1000 instrument. The patients were also assessed for their subjective complaints using IKDC (International Knee Documentation Committee) Knee Scoring System.

RESULTS

The strength and endurance index of the quadriceps and hamstrings recovered and improved by the sixth month after surgery. The recovery by the quadriceps muscle is more marked and by the sixth month, it has recovered to more than the preoperative level. As for laxity, the average side-to-side difference at 30 pounds was 2.75 mm by 6 months. Of these patients, the side-to-side difference was less than 5 mm in 66 patients (5 mm as taken to be acceptable for graft success). As for IKDC rating, at the sixth month, 71 patients had normal or near normal knee by their own assessment. No patients had anterior knee pain at rest. Sensory deficits were only present in 3 patients with complaints of numbness over the distribution of the saphenous nerve or its infrapatellar branch.

CONCLUSION

Most morbidities are temporal in nature and do not significantly affect the patient's activities.