Anshu Malhotra

NK cells: immune cross-talk and therapeutic implications

Increased evidence of cross-talk between NK cells and other immune cells has enhanced the possibilities of exploiting the interplay between the activation and inhibition of NK cells for immunotherapeutic purposes. The battery of receptors possessed by NK cells help them to efficiently detect aberrant and infected cells and embark on the signaling pathways necessary to eliminate them. Endogenous expansion of NK cells and their effector mechanisms are under exploration for enhancing adoptive immunotherapy prospects in combination with immunostimulatory and cell-death-sensitizing treatments against cancer, viral infections and other pathophysiological autoimmune conditions. Various modes of NK cell manipulation are being undertaken to overcome issues such as relapse and graft rejections associated with adoptive immunotherapy. While tracing the remarkable properties of NK cells and the major developments in this field, we highlight the role of immune cooperativity in the betterment of current immunotherapeutic approaches.

Resuscitating cancer immunosurveillance: selective stimulation of DLL1-Notch signaling in T cells rescues T cell function and inhibits tumor growth

Deficiencies in immune function that accumulate during cancer immunoediting lead to a progressive escape from host immunosurveillance. Therapies that correct or overcome these defects could have a powerful impact on cancer management, but current knowledge of the types and mechanisms of immune escape is still incomplete. Here, we report a novel mechanism of escape from T-cell immunity that is caused by reduction in levels of the Delta family Notch ligands DLL1 and DLL4 in hematopoietic microenvironments. An important mediator of this effect was an elevation in the levels of circulating VEGF. Selective activation of the DLL1-Notch signaling pathway in bone marrow precursors enhanced T-cell activation and inhibited tumor growth. Conversely, tumor growth led to inhibition of Delta family ligand signaling through Notch in the hematopoietic environment, resulting in suppressed T-cell function. Overall, our findings uncover a novel mechanism of tumoral immune escape and suggest that a soluble multivalent form of DLL1 may offer a generalized therapeutic intervention to stimulate T-cell immunity and suppress tumor growth.

Challenges and future perspectives of T cell immunotherapy in cancer

Since the formulation of the tumour immunosurveillance theory, considerable focus has been on enhancing the effectiveness of host antitumour immunity, particularly with respect to T cells. A cancer evades or alters the host immune response by various ways to ensure its development and survival. These include modifications of the immune cell metabolism and T cell signalling. An inhibitory cytokine milieu in the tumour microenvironment also leads to immune suppression and tumour progression within a host. This review traces the development in the field and attempts to summarize the hurdles that the approach of adoptive T cell immunotherapy against cancer faces, and discusses the conditions that must be improved to allow effective eradication of cancer.

Sonic Hedgehog Signaling Drives Mitochondrial Fragmentation by Suppressing Mitofusins in Cerebellar Granule Neuron Precursors and Medulloblastoma

Sonic hedgehog (Shh) signaling is closely coupled with bioenergetics of medulloblastoma, the most common malignant pediatric brain tumor. Shh-associated medulloblastoma arises from cerebellar granule neuron precursors (CGNP), a neural progenitor whose developmental expansion requires signaling by Shh, a ligand secreted by the neighboring Purkinje neurons. Previous observations show that Shh signaling inhibits fatty acid oxidation although driving increased fatty acid synthesis. Proliferating CGNPs and mouse Shh medulloblastomas feature high levels of glycolytic enzymes in vivo and in vitro. Because both of these metabolic processes are closely linked to mitochondrial bioenergetics, the role of Shh signaling in mitochondrial biogenesis was investigated. This report uncovers a surprising decrease in mitochondrial membrane potential (MMP) and overall ATP production in CGNPs exposed to Shh, consistent with increased glycolysis resulting in high intracellular acidity, leading to mitochondrial fragmentation. Ultrastructural examination of mitochondria revealed a spherical shape in Shh-treated cells, in contrast to the elongated appearance in vehicle-treated postmitotic cells. Expression of mitofusin 1 and 2 was reduced in these cells, although their ectopic expression restored the MMP to the nonproliferating state and the morphology to a fused, interconnected state. Mouse Shh medulloblastoma cells featured drastically impaired mitochondrial morphology, restoration of which by ectopic mitofusin expression was also associated with a decrease in the expression of Cyclin D2 protein, a marker for proliferation. Implications: This report exposes a novel role for Shh in regulating mitochondrial dynamics and rescue of the metabolic profile of tumor cells to that of nontransformed, nonproliferating cells and represents a potential avenue for development of medulloblastoma therapeutics. Mol Cancer Res; 14(1); 114–24. ©2015 AACR.

YB-1 is elevated in medulloblastoma and drives proliferation in Sonic hedgehog - dependent cerebellar granule neuron progenitor cells and medulloblastoma cells

Postnatal proliferation of cerebellar granule neuron precursors (CGNPs), proposed cells of origin for the SHH-associated subgroup of medulloblastoma, is driven by Sonic hedgehog (Shh) and insulin-like growth factor (IGF) in the developing cerebellum. Shh induces the oncogene Yes-associated protein (YAP), which drives IGF2 expression in CGNPs and mouse Shh-associated medulloblastomas. To determine how IGF2 expression is regulated downstream of YAP, we carried out an unbiased screen for transcriptional regulators bound to IGF2 promoters. We report that Y-box binding protein-1 (YB-1), an onco-protein regulating transcription and translation, binds to IGF2 promoter P3. We observed that YB-1 is upregulated across human medulloblastoma subclasses as well as in other varieties of pediatric brain tumors. Utilizing the cerebellar progenitor model for the Shh subgroup of medulloblastoma in mice, we show for the first time that YB-1 is induced by Shh in CGNPs. Its expression is YAP-dependent and it is required for IGF2 expression in CGNPs. Finally, both gain-of function and loss-of-function experiments reveal that YB-1 activity is required for sustaining CGNP and medulloblastoma cell (MBC) proliferation. Collectively, our findings describe a novel role for YB-1 in driving proliferation in the developing cerebellum and MBCs and they identify the SHH:YAP:YB1:IGF2 axis as a powerful target for therapeutic intervention in medulloblastomas.

WIP1 modulates responsiveness to Sonic Hedgehog signaling in neuronal precursor cells and medulloblastoma

High-level amplification of the protein phosphatase PPM1D (WIP1) is present in a subset of medulloblastomas (MBs) that have an expression profile consistent with active Sonic Hedgehog (SHH) signaling. We found that WIP1 overexpression increased expression of Shh target genes and cell proliferation in response to Shh stimulation in NIH3T3 and cerebellar granule neuron precursor cells in a p53-independent manner. Thus, we developed a mouse in which WIP1 is expressed in the developing brain under control of the Neurod2 promoter (ND2:WIP1). The external granule layer (EGL) in early postnatal ND2:WIP1 mice exhibited increased proliferation and expression of Shh downstream targets. MB incidence increased and survival decreased when ND2:WIP1 mice were crossed with an Shh-activated MB mouse model. Conversely, Wip1 knockout significantly suppressed MB formation in two independent mouse models of Shh-activated MB. Furthermore, Wip1 knockdown or treatment with a WIP1 inhibitor suppressed the effects of Shh stimulation and potentiated the growth inhibitory effects of SHH pathway-inhibiting drugs in Shh-activated MB cells in vitro. This suggests an important cross-talk between SHH and WIP1 pathways that accelerates tumorigenesis and supports WIP1 inhibition as a potential treatment strategy for MB.

Ecological morphotaxometry of trematodes of garfish (Teleostomi: Belonidae) from Gangetic riverine ecosystem in India. I. Morphology and taxometric assessment of Cephalogonimus yamunii n.sp.

A new endoparasitic fluke, Cephalogonimus yamunii n.sp. is described from the intestine of freshwater fish Xenentodon cancilla (Belonidae). The worms could be differentiated from C. amphiumae (Chandler 1932), C. apognichthysi (Gupta and Puri 1982), C. hanumanthai (Agrawal and Agarwal 1984), C. salamandrus (Dronen and Lang 1974), C. simhai (Singh 2010) and C. vesicaudus (Nickerson 1912) in a unipartite seminal vesicle, genital pore subterminal anteriorly, opening at the hind end of oral sucker, equatorial or sub-equatorial testes, besides other morphological attributes of shorter body and pharynx, larger oesophagus and oral sucker, smaller ventral sucker, testes, cirrus sac and ovary, and a terminal excretory pore. Taxometric substantiation has been presented by using Polythetic Divisive Classificatory System, and ecological attributes have been evaluated to validate specific distribution patterns in population dynamics of the new species in simultaneous contributions.

A new species of Neolebouria Gibson, 1976 (Opecoelidae: Plagioporinae) from the whitecheek monocle bream, Scolopsis vosmeri (Perciformes: Nemipteridae), from the Panjim coast at Goa, with a checklist of parasites previously reported from this fish

Neolebouria capoori n. sp. (Opecoelidae: Plagioporinae) is described from the whitecheek monocle bream, Scolopsis vosmeri (Bloch) (Perciformes: Nemipteridae) from the Panjim coast on the central west coast of India at Goa. The new species differs from both Neolebouria cantherhini (Li, Qiu & Zhang, 1988) as originally described from Thamnaconus modestus (Günther) (syn. Cantherines modestus Günther ) and Neolebouria confusum (Overstreet, 1969) as originally described from Ocyurus chrysurus (Bloch) by having the cirrus sac surpassing the ventral sucker posteriorly in N. cantherhini and being entirely preacetabular in N. confusum compared to terminating near the midlevel of the ventral sucker in N. capoori n. sp. The new species is most similar to N. confusum, but it further differs from this species by having the vitelline fields terminating near the level of the esophageal bifurcation compared to terminating near the level of the posterior margin of the pharynx, a larger sucker ratio (1:1.7-1:2.0 compared to 1:1.4-1:1.7), a somewhat shorter cirrus sac relative to body length (160-448, representing 9-18% of the body length compared to about 367, representing 22%), and the egg of the new species has a boss at the anopercular end that is not present in N. confusum. This study represents the first report on an opecoelid from S. vosmeri. A review of the parasites reported from S. vosmeri is included.

Abstract B12: Yes-Associated Protein: A master metabolic regulator In medulloblastoma

Downstream of mitogenic Sonic hedgehog (Shh) signaling, Yes-Associated Protein (YAP) can drive proliferation in Cerebellar Granule Neural Progenitor (CGNP) cells. CGNPs are the proposed cells of origin of SHH medulloblastomas. They are a neural progenitor type whose developmental expansion requires signaling by Shh, a secreted ligand produced by the neighboring Purkinje neurons. Approximately 30% of human medulloblastomas bear an activated Sonic hedgehog pathway gene expression signature. Ectopic expression of YAP promotes highly aggressive Shh-driven medulloblastoma growth and radio-resistance (Fernandez et al., 2009). Medulloblastoma being the most common solid malignancy of childhood and a leading cause of pediatric mortality, the current standard of care results in about 60% “cure” rate. But the survivors are beset with long-term side effects, including cognitive impairment, seizures, premature aging, and susceptibility to cancer. Moreover, recurrence and metastasis are lethal. Therefore, identification of novel modes of molecular targeted therapies is critical for the improved quality of life for survivors and reduced incidence of recurrence and metastasis. Recently, there has been renewed interest in how altered metabolic patterns in tumors could be exploited for therapeutic purposes. Deregulating the metabolic machinery for aberrant energy utilization is one of the hallmarks of a proliferating cancer cell. Previously, our lab made the novel observation that Shh mitogenic/oncogenic signaling is tightly coupled to the reprogramming of mitochondrial bioenergetics: Shh inhibits fatty acid oxidation (FAO, or β-oxidation) while driving increased fatty acid synthesis (FAS), an early step of lipogenesis. The production of citrate, an essential component for fatty acid synthesis, occurs inside the mitochondrion via the Tri-carboxylic acid cycle (TCA). We analyzed the effect of Shh treatment and ectopic YAP expression on CGNPs and found that YAP increases levels of fatty acid synthase (FASN) and ATP citrate lyase (ACLY), while YAP knock-down in Shh-treated CGNPs resulted in reduced levels of these enzymes. Moreover, we also observed a surprising decrease in mitochondrial membrane potential. This prompted us to further analyze the ultrastructure of mitochondria using Transmission Electron Microscopy. Shh-treated or ectopic YAP-expressing mitochondria presented a swollen morphology, along with an expanded matrix space and deformed cristae structure, typical of morphologically aberrant mitochondria. These differences in mitochondrial structure were also visible in ultrastructures of SmoA1 tumor tissue as well as in vitro cultures of SmoA1 tumor cells (MBCs). Being dynamic structures, mitochondria undergo constant fusion and fission events, which contribute to their biogenesis. Expression of fusion genes Mitofusin 1 and 2 was reduced while DRP1, a fission promoting gene was highly induced in all samples under study. Ectopic expression of Mitofusin 1 and 2, and knock down of DRP1 in CGNPs and MBCs not only restores the membrane potential to the non-proliferating state, but also indicates a reduction in proliferation. Our study thus implicates YAP-regulated metabolic pathways and enzymes as potential targets for novel medulloblastoma therapies. Our goal is to determine whether hampering YAP-mediated mitochondrial fragmentation can restore the metabolic profile of tumor cells to that of non-transformed, non-proliferating cells, thus suggesting a potential novel treatment paradigm that may reduce or eliminate the requirement for high dose radiation. Citation Format: Anshu Malhotra, Abhinav Dey, Anna Marie Kenney. Yes-Associated Protein: A master metabolic regulator In medulloblastoma. [abstract]. In: Proceedings of the AACR Special Conference: Metabolism and Cancer; Jun 7-10, 2015; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(1_Suppl):Abstract nr B12.

Bioinvasion: a paradigm shift from marine to inland ecosystems

Anisakidosis is one of the most fearsome zoonotic food borne disease in aquaculture. The natural infections by anisakidoids or related variety in freshwater fish are not known, though sporadic experimental reports are available abroad (Butcher and Shamsi 2011). Invasive severity of anisakidoids in fish from Gangetic riverine ecosystems, i.e., in river Ganges at Fatehpur and Allahabad, as well as in river Yamuna at Allahabad, and molecular heterogeneity among these worms have been extensively investigated. The pathways of transmission of non-native alien species due to long distance migratory habits of Rita rita, man-made alterations including dredging in long stretches of the river bed of Ganges to facilitate ballast water transfer mechanism owing to the commercial ship movements between Haldia and Allahabad; and sudden water chemistry (salinity, hardness, alkalinity) alteration (due particularly to rainy period) oriented micro-fauna interchange are identified, and remedial measures suggested.