A Multistep Tumor Growth Model of High-Grade Serous Ovarian Carcinoma Identifies Hypoxia-Associated Signatures

High-grade serous ovarian carcinoma (HGSC) is associated with late-stage disease presentation and poor prognosis, with a limited understanding of early transformation events. Our study analyzes HGSC tumor progression and organ-specific metastatic dissemination to identify hypoxia-associated molecular, cellular, and histological alterations. Clinical characteristics of the HGSC were replicated in orthotopic xenografts, which involve metastatic dissemination and the prevalence of group B tumors (volume: >0.0625 ≤ 0.5 cm3). Enhanced hyaluronic acid (HA) deposition, expanded tumor vasculature, and increased necrosis contributed to the remodeling of tumor tissue architecture. The proliferative potential of tumor cells and the ability to form glands were also altered during tumor growth. Flow cytometry and label chase-based molecular profiling across the tumor regenerative hierarchy identified the hypoxia-vasculogenic niche and the hybrid epithelial-mesenchymal tumor-cell state as determinants of self-renewal capabilities of progenitors and cancer stem cells. A regulatory network and mathematical model based on tumor histology and molecular signatures predicted hypoxia-inducible factor 1-alpha (HIF1A) as a central node connecting HA synthesis, epithelial-mesenchymal transition, metabolic, vasculogenic, inflammatory, and necrotic pathways in HGSC tumors. Thus, our findings provide a temporal resolution of hypoxia-associated events that sculpt HGSC tumor growth; an in-depth understanding of it may aid in the early detection and treatment of HGSC.

A monoclonal antibody against annexin A2 targets stem and progenitor cell fractions in tumors

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Development of a novel antibody (termed as mAb150) developed in our lab which targets annexin A2.

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Although there are earlier reports of another monoclonal antibody with the same target, the epitope recognized by mAb150 is novel.

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mAb150 is specifically recognized to target the achilles heel of cancer viz. cancer stem cells and progenitors that persist after treatments and potentially give rise to minimal residual disease.

The involvement of cancer stem cells (CSCs) in driving tumor dormancy and drug resistance is well established. Most therapeutic regimens however are ineffective in targeting these regenerative populations. We report the development and evaluation of a monoclonal antibody, mAb150, which targets the metastasis associated antigen, Annexin A2 (AnxA2) through recognition of a N-terminal epitope. Treatment with mAb150 potentiated re-entry of CSCs into the cell cycle that perturbed tumor dormancy and facilitated targeting of CSCs as was validated by in vitro and in vivo assays. Epigenetic potentiation further improved mAb150 efficacy in achieving total tumor regression by targeting regenerative populations to achieve tumor regression, specifically in high-grade serous ovarian adenocarcinoma.

Functional balance between Tcf21-Slug defines cellular plasticity and migratory modalities in high grade serous ovarian cancer cell lines

Cellular plasticity and transitional phenotypes add to complexities of cancer metastasis that can be initiated by single cell epithelial to mesenchymal transition (EMT) or cooperative cell migration (CCM). Our study identifies novel regulatory cross-talks between Tcf21 and Slug in mediating phenotypic and migration plasticity in high-grade serous ovarian adenocarcinoma (HGSC). Differential expression and subcellular localization associate Tcf21, Slug with epithelial, mesenchymal phenotypes, respectively; however, gene manipulation approaches identify their association with additional intermediate phenotypic states, implying the existence of a multistep epithelial-mesenchymal transition program. Live imaging further associated distinct migratory modalities with the Tcf21/Slug status of cell systems and discerned proliferative/passive CCM, active CCM and EMT modes of migration. Tcf21-Slug balance identified across a phenotypic spectrum in HGSC cell lines, associated with microenvironment-induced transitions and the emergence of an epithelial phenotype following drug exposure. Phenotypic transitions and associated functionalities following drug exposure were affirmed to ensue from occupancy of Slug promoter E-box sequences by Tcf21. Our study effectively provides a framework for understanding the relevance of ovarian cancer plasticity as a function of two transcription factors.

A tumor deconstruction platform identifies definitive end points in the evaluation of drug responses

Tumor heterogeneity and the presence of drug-sensitive and refractory populations within the same tumor are almost never assessed in the drug discovery pipeline. Such incomplete assessment of drugs arising from spatial and temporal tumor cell heterogeneity reflects on their failure in the clinic and considerable wasted costs in the drug discovery pipeline. Here we report the derivation of a flow cytometry-based tumor deconstruction platform for resolution of at least 18 discrete tumor cell fractions. This is achieved through concurrent identification, quantification and analysis of components of cancer stem cell hierarchies, genetically instable clones and differentially cycling populations within a tumor. We also demonstrate such resolution of the tumor cytotype to be a potential value addition in drug screening through definitive cell target identification. Additionally, this real-time definition of intra-tumor heterogeneity provides a convenient, incisive and analytical tool for predicting drug efficacies through profiling perturbations within discrete tumor cell subsets in response to different drugs and candidates. Consequently, possible applications in informed therapeutic monitoring and drug repositioning in personalized cancer therapy would complement rational design of new candidates besides achieving a re-evaluation of existing drugs to derive non-obvious combinations that hold better chances of achieving remission.

First Report of Leaf Spot Caused by Phoma costarricensis on Delphinium malabaricum in Western Ghats of India

Delphinium L. is a genus of more than 300 species of perennial flowering plants belonging to the family Ranunculaceae and is native throughout the Northern Hemisphere. In India, 24 species are found mainly in the Himalayan regions. Delphinium malabaricum (Huth) Munz is the only species of the genus endemic to northern Western Ghats. Its mediumsized violet-to-metallic blue spurred flowers have considerable ornamental value as a floriculture crop (3). There is no report of serious diseases of this genus in India. Since 2008, a severe foliar disease was observed each year on D. malabaricum cultivated on the experimental plots located at Shivaji University, Kolhapur, India. Symptoms were small, necrotic spots on the abaxial and adaxial sides of infected leaves, with spots enlarging to form round areas that were 6 to 9 mm in diameter and well defined by a dark black margin. Severely infected leaves wilted without abscising. No symptoms were observed on other plant parts. From infected leaves, a fungus was isolated on Czapek Dox agar (CDA) amended with 25 mg/liter of streptomycin sulfate. The fungus was grown on CDA and cultures were maintained at 4°C for further studies. After 6 days, black pycnidia developed, which were variable in size, releasing abundant hyaline, elliptical conidia measuring from 3 to 4 × 1.5 to 2 μm. On the basis of cultural and morphological characteristics, the fungus was identified as Phoma costarricensis (1,2). The identification was verified by sequencing a region of 28S ribosomal RNA with the geneOmbio LSU gene sequencing primers and ABI BigDye Terminator v3.1 Cycle Sequencing Reaction Kit (Applied Biosystems, Carlsbad, CA). The sequence was deposited as Accession No. HE608244 in EMBL-Bank. Blast analysis of the sequence obtained showed a 99% homology with several isolates of P. costarricensis in the GenBank database (Accession No. GU238058.1). Pathogenicity tests were performed by spraying leaves of 10 healthy plants with spores (~10,000 spores or mycelial fragments per ml) on the abaxial and adaxial surface of leaves. Noninoculated plants served as control. Symptoms identical to those on field samples developed on all inoculated plants 1 week after inoculation but controls remained asymptomatic during the observation period. P. costarricensis was reisolated from inoculated symptomatic plants and the identity was confirmed, which completed Koch's postulates. This experiment was repeated three times in a greenhouse, confirming the pathogenicity of P. costarricensis on D. malabaricum. P. ajacis (Thum.) Aa & Boerema, P. delphinii (Rabenh.) Cooke, P. aquilegiicola M. Petrov, and P. xanthina Sacc. are reported to cause leaf spot and stem rot in Delphinium spp. (1). However, to our knowledge, there are no previous reports of leaf spot of D. malabaricum caused by P. costarricensis. Leaf spot severity induced premature defoliation, leading to reduction in flower setting and ultimately the yield. The disease could lead to an economic crisis in the farmer community of western India. The only other known host of P. costarricensis is Coffea arabica (2). References: (1) G. H. Boerema et al. Phoma Identification Manual. CABI Publishing, Wallingford, UK and Cambridge, MA, 2004. (2) E. Echandi. Rev. Biol. Trop. 5:83, 1957. (3) S. R. Pai et al. Cytologia 72:319, 2007.

Spectrum of CREBBP mutations in Indian patients with Rubinstein-Taybi syndrome

Rubinstein-Taybi syndrome (RSTS), a developmental disorder comprising abnormalities that include mental retardation, an unusual facial appearance, broad thumbs and big toes is frequently associated with molecular lesions in the CREB-binding protein gene, CREBBP. The objective of the present study was to identify and analyse CREBBP mutations in Indian RSTS patients on which there are no data. Direct sequencing of CREBBP performed in 13 RSTS patients identified the three zinc fingers (CH1, CH2, CH3) and HAT domain as mutational hotspots in which ten novel pathogenic mutations were localized. Functional analysis revealed that three of these mutations affecting amino acids Glu1459, Leu1668 and Glu1724 were critical for histone acetyltransferase activity. Twenty-eight novel CREBBP single-nucleotide polymorphisms (SNPs) were also identified in the Indian population. Linkage disequilibrium studies revealed associations between (i) SNP (rs129974/c.3836-206G greater than C) and mutation (p.Asp1340Ala); (ii) (rs130002) with mutation (p.Asn435Lys) and (iii) SNPs rs129974, rs130002 and SNP (c.3836-206G greater than C) signifying a disease affection status. In conclusion, the present study reports the highest detection rate of CREBBP mutations (76.9%) in RSTS patients to date, of which ten are predicted to be pathogenic and three critical for histone acetyltransferase activity. Moreover, identification of the association of CREBBP polymorphisms with disease susceptibility could be an important risk factor for the pathogenesis of RSTS.

CD133-expressing stem cells associated with ovarian metastases establish an endothelial hierarchy and contribute to tumor vasculature

Recruitment and localization of endothelial precursors within tumors is a potential area for the development of therapeutics, because their functional contribution to tumor vasculature is realized to be important for cancer cell survival. However, the exact nature of the recruited cell type and cellular events orchestrating the entire phenomenon remains obscure. We report that human ovarian cancer is frequently associated with cells expressing the stem cell surface marker CD133. We further show that these CD133-expressing cells are nontumorigenic in nature, and they augment tumor development through their vasculogenic potential. This cell population is attracted by cancer stem cells (CSCs) and retains a direct physical association within the CSC-derived spheroids. Our study further delineates the contribution of these vasculogenic CD133(+) stem cells, termed by us as endothelial stem cells (EnSCs) to the developing tumor vasculature during disease progression. In support of their being stem cells, the EnSCs have a capability of establishing an entire endothelial cell hierarchy. We conclude that such EnSCs play a crucial role in ensuring the development of long-term tumor vasculature to complement CSC-driven tumor development and disease progression.

Stem and progenitor-like cells contribute to the aggressive behavior of human epithelial ovarian cancer

The cellular mechanisms underlying the increasing aggressiveness associated with ovarian cancer progression are poorly understood. Coupled with a lack of identification of specific markers that could aid early diagnoses, the disease becomes a major cause of cancer-related mortality in women. Here we present direct evidence that the aggressiveness of human ovarian cancer may be a result of transformation and dysfunction of stem cells in the ovary. A single tumorigenic clone was isolated among a mixed population of cells derived from the ascites of a patient with advanced ovarian cancer. During the course of the study, yet another clone underwent spontaneous transformation in culture, providing a model of disease progression. Both the transformed clones possess stem cell-like characteristics and differentiate to grow in an anchorage-independent manner in vitro as spheroids, although further maturation and tissue-specific differentiation was arrested. Significantly, tumors established from these clones in animal models are similar to those in the human disease in their histopathology and cell architecture. Furthermore, the tumorigenic clones, even on serial transplantation continue to establish tumors, thereby confirming their identity as tumor stem cells. These findings suggest that: (a) stem cell transformation can be the underlying cause of ovarian cancer and (b) continuing stochastic events of stem and progenitor cell transformation define the increasing aggression that is characteristically associated with the disease.