Anamika Bose

Sunitinib facilitates the activation and recruitment of therapeutic anti-tumor immunity in concert with specific vaccination

The multikinase inhibitor sunitinib malate (SUT) has been reported to reduce levels of myeloid suppressor cells and Treg cells in cancer patients, hypothetically diminishing intrinsic impediments for active immunization against tumor‐associated antigens in such individuals. The goal of this study was to identify longitudinal immune molecular and cellular changes associated with tumor regression and disease‐free status after the treatment of established day 7 s.c. MO5 (B16.OVA) melanomas with SUT alone (1 mg/day via oral gavage for 7 days), vaccination using ovalbumin (OVA) peptide‐pulsed dendritic cell [vaccine (VAC)] alone, or the combination of SUT and VAC (SUT/VAC). We observed superior anti‐tumor efficacy for SUT/VAC combination approaches, particularly when SUT was applied at the time of the initial vaccination or the VAC boost. Treatment effectiveness was associated with the acute loss of (and/or failure to recruit) cells bearing myeloid‐derived suppressor cells or Treg phenotypes within the tumor microenvironment (TME) and the corollary, prolonged enhancement of Type‐1 anti‐OVA CD8+ T cell responses in the tumor‐draining lymph node and the TME. Enhanced Type‐1 T cell infiltration of tumors was associated with treatment‐induced expression of vascular cell adhesion molecule‐1 (VCAM‐1) and CXCR3 ligand chemokines in vascular/peri‐vascular cells within the TME, with SUT/VAC therapy benefits conditionally negated upon adminsitration of CXCR3 or VCAM‐1 blocking antibodies. These data support the ability of a short 7 day course of SUT to (re)condition the TME to become more receptive to the recruitment and prolonged therapeutic action of (VAC‐induced) anti‐tumor Tc1 cells.

Combined vaccine+axitinib therapy yields superior antitumor efficacy in a murine melanoma model.

Axitinib, a tyrosine kinase inhibitor of vascular endothelial growth factor receptors, has demonstrated modest efficacy when applied as a single agent in the setting of advanced-stage melanoma. On the basis of the reported ability of axitinib to ‘normalize’ the tumor vasculature, we hypothesize that combination therapy using axitinib plus specific peptide-based vaccination would promote superior activation and recruitment of protective T cells into the melanoma microenvironment, leading to enhanced treatment benefit. Using a subcutaneous M05 (B16.OVA) melanoma model, we observed that a treatment regimen consisting of a 7-day course of axitinib (0.5 mg/day provided orally) combined with a subcutaneous vaccine [ovalbumin (OVA) peptide-pulsed syngenic dendritic cells adenovirally engineered to produce IL-12p70] yielded superior protection against melanoma growth and extended overall survival when compared with animals receiving either single modality therapy. Treatment benefits were associated with: (a) a reduction in suppressor cell (myeloid-derived suppressor cells and Treg) populations in the tumor, (b) activation of tumor vascular endothelial cells, and (c) activation and recruitment of type-1, vaccine-induced CD8+ T cells into tumors. These results support the therapeutic superiority of combined vaccine+axitinib immunotherapy and the translation of such approaches into the clinic for the treatment of patients with advanced-stage melanoma.

Neem leaf glycoprotein restores the impaired chemotactic activity of peripheral blood mononuclear cells from head and neck squamous cell carcinoma patients by maintaining CXCR3/CXCL10 balance

Interaction between CXCL10 and CXCR3 is dysregulated in head and neck squamous cell carcinoma (HNSCC) and hampers chemotaxis of cytotoxic cells at tumor site. In continuation of the demonstration of significant immunomodulatory effects of neem leaf preparation (NLP), the active ingredient of NLP is characterized as a glycoprotein (NLGP). NLGP is responsible for in vivo immunomodulation to restrict the growth of mice tumors. Effect of NLGP in rectification of the dysregulated IFN gamma dependent chemokine and its receptor CXCR3 splice variants was investigated. Upregulated expression of CXCR3B in HNSCC-PBMC were downregulated following in vitro NLGP treatment. Unchanged expression of CXCR3A+B by NLGP with downregulation of the CXCR3B indirectly suggests the upregulation of the CXCR3A, responsible for cellular migration. However, stimulation of healthy-PBMC with NLGP maintains physiological homeostasis of CXCL10 and increases IFN gamma secretion. The suppressed chemotaxis of HNSCC-PBMC could be restored either by in vitro treatment with NLGP or during use of NLGP stimulated PBMC supernatant as a chemoattractant. Neutralization studies confirmed that the chemoattraction process is guided by both receptor (CXCR3A) and its ligand (CXCL10). Neutralization of the IFN gamma in PBMC culture in presence of NLGP unexpectedly increases the intracellular release of CXCL10, suggesting the NLGP mediated IFN gamma independent release of CXCL10. Interestingly, downregulation of the CXCL10 release was detected after IFN gamma neutralization in absence of NLGP and IFN gamma receptor neutralization in presence of NLGP. Efficacy of NLGP in restoration of the dysregulation of the chemokine signaling may be utilized to design new immunotherapeutic protocol.

Intratumoral IL-12 Gene Therapy Results in the Crosspriming of Tc1 Cells Reactive Against Tumor-associated Stromal Antigens

HLA-A2 transgenic mice bearing established HLA-A2(neg) B16 melanomas were effectively treated by intratumoral (i.t.) injection of syngeneic dendritic cells (DCs) transduced to express high levels of interleukin (IL)-12, resulting in CD8(+) T cell-dependent antitumor protection. In this model, HLA-A2-restricted CD8(+) T cells do not directly recognize tumor cells and therapeutic benefit was associated with the crosspriming of HLA-A2-restricted type-1 CD8(+) T cells reactive against antigens expressed by stromal cells [i.e., pericytes and vascular endothelial cells (VEC)]. IL-12 gene therapy-induced CD8(+) T cells directly recognized HLA-A2(+) pericytes and VEC flow-sorted from B16 tumor lesions based on interferon (IFN)-γ secretion and translocation of the lytic granule-associated molecule CD107 to the T cell surface after coculture with these target cells. In contrast, these CD8(+) T effector cells failed to recognize pericytes/VEC isolated from the kidneys of tumor-bearing HHD mice. The tumor-associated stromal antigen (TASA)-derived peptides studied are evolutionarily conserved and could be recognized by CD8(+) T cells harvested from the blood of HLA-A2(+) normal donors or melanoma patients after in vitro stimulation. These TASA and their derivative peptides may prove useful in vaccine formulations against solid cancers, as well as, in the immune monitoring of HLA-A2(+) cancer patients receiving therapeutic interventions, such as IL-12 gene therapy.

Neem leaf glycoprotein helps to generate carcinoembryonic antigen specific anti-tumor immune responses utilizing macrophage-mediated antigen presentation

In an objective to generate effective carcinoembryonic antigen (CEA) specific anti-tumor immune response in Swiss mice, CEA was presented using macrophages with adjuvant help from neem leaf glycoprotein (NLGP). Such vaccination generates significantly higher antibody (IgG2a) and T cell response than immunization protocol without NLGP. NLGP controls the function of both B cells and macrophages by altering the expressions of various regulatory molecules, like, CD19, CD11b, etc. NLGP also directs CEA vaccination towards Th1 bias, by modulating cytokine secretion. This NLGP-generated anti-CEA immune response would be effective as a vaccine to lyse CEA(+) tumors in vitro and in vivo.

Neem leaf glycoprotein matures myeloid derived dendritic cells and optimizes anti-tumor T cell functions

In an objective to find out an effective, nontoxic dendritic cell (DC) maturating agent for human use, CD14(+) monocytes were differentiated with GMCSF/IL-4 and matured with neem leaf glycoprotein (NLGP). NLGP matured DCs (NLGP-DCs) show upregulated expression of CD83, CD80, CD86, CD40 and MHCs, in a comparable extent of control, LPS. NLGP-DCs secrete high amount of IL-12p70 with low IL-10. NLGP upregulates the expression of crucial transcription factor, ikaros, indicating maturation towards DC1 phenotype. Increased expression of CD28 and CD40L on T cells following co-culture with NLGP-DCs was noticed to promote DC-T interactions. As a result, T cells secrete high amount of IFN gamma with low IL-4 and generates anti-tumor type 1 immune microenvironment. Such NLGP-DCs present carcinoembryonic antigen (CEA) effectively to T cells to increase T cell mediated cytotoxicity of CEA(+) tumor cells in vitro and in vivo. With emergence of the NLGP as a promising DC maturating agent, NLGP-DCs can be used as a candidate vaccine tool for antigen specific cancer immunotherapy.

Vaccines Targeting Tumor Blood Vessel Antigens Promote CD8+ T Cell-Dependent Tumor Eradication or Dormancy in HLA-A2 Transgenic Mice

We have recently shown that effective cytokine gene therapy of solid tumors in HLA-A2 transgenic (HHD) mice lacking murine MHC class I molecule expression results in the generation of HLA-A2–restricted CD8+ T effector cells selectively recognizing tumor blood vessel-associated pericytes and/or vascular endothelial cells. Using an HHD model in which HLA-A2neg tumor (MC38 colon carcinoma or B16 melanoma) cells are not recognized by the CD8+ T cell repertoire, we now show that vaccines on the basis of tumor-associated blood vessel Ags (TBVA) elicit protective Tc1-dependent immunity capable of mediating tumor regression or extending overall survival. Vaccine efficacy was not observed if (HLA-A2neg) wild-type C57BL/6 mice were instead used as recipient animals. In the HHD model, effective vaccination resulted in profound infiltration of tumor lesions by CD8+ (but not CD4+) T cells, in a coordinate reduction of CD31+ blood vessels in the tumor microenvironment, and in the “spreading” of CD8+ T cell responses to alternate TBVA that were not intrinsic to the vaccine. Protective Tc1-mediated immunity was durable and directly recognized pericytes and/or vascular endothelial cells flow-sorted from tumor tissue but not from tumor-uninvolved normal kidneys harvested from these same animals. Strikingly, the depletion of CD8+, but not CD4+, T cells at late time points after effective therapy frequently resulted in the recurrence of disease at the site of the regressed primary lesion. This suggests that the vaccine-induced anti-TBVA T cell repertoire can mediate the clinically preferred outcomes of either effectively eradicating tumors or policing a state of (occult) tumor dormancy.

Neem Leaf Glycoprotein Activates CD8 + T Cells to Promote Therapeutic Anti-Tumor Immunity Inhibiting the Growth of Mouse Sarcoma

In spite of sufficient data on Neem Leaf Glycoprotein (NLGP) as a prophylactic vaccine, little knowledge currently exists to support the use of NLGP as a therapeutic vaccine. Treatment of mice bearing established sarcomas with NLGP (25 µg/mice/week subcutaneously for 4 weeks) resulted in tumor regression or dormancy (Tumor free/Regressor, 13/24 (NLGP), 4/24 (PBS)). Evaluation of CD8+ T cell status in blood, spleen, TDLN, VDLN and tumor revealed increase in cellular number. Elevated expression of CD69, CD44 and Ki67 on CD8+ T cells revealed their state of activation and proliferation by NLGP. Depletion of CD8+ T cells in mice at the time of NLGP treatment resulted in partial termination of tumor regression. An expansion of CXCR3+ and CCR5+ T cells was observed in the TDLN and tumor, along with their corresponding ligands. NLGP treatment enhances type 1 polarized T-bet expressing T cells with downregulation of GATA3. Treg cell population was almost unchanged. However, T∶Treg ratios significantly increased with NLGP. Enhanced secretion/expression of IFNγ was noted after NLGP therapy. In vitro culture of T cells with IL-2 and sarcoma antigen resulted in significant enhancement in cytotoxic efficacy. Consistently higher expression of CD107a was also observed in CD8+ T cells from tumors. Reinoculation of sarcoma cells in tumor regressed NLGP-treated mice maintained tumor free status in majority. This is correlated with the increment of CD44hiCD62Lhi central memory T cells. Collectively, these findings support a paradigm in which NLGP dynamically orchestrates the activation, expansion, and recruitment of CD8+ T cells into established tumors to operate significant tumor cell lysis.

Neem leaf glycoprotein enhances carcinoembryonic antigen presentation of dendritic cells to T and B cells for induction of anti-tumor immunity by allowing generation of immune effector/memory response.

Vaccination with neem leaf glycoprotein matured carcinoembryonic antigen (CEA) pulsed dendritic cells (DCs) enhances antigen-specific humoral and cellular immunity against CEA and restricts the growth of CEA(+) murine tumors. NLGP helps better CEA uptake, processing and presentation to T/B cells. This vaccination (DCNLGPCEA) elicits mitogen induced and CEA specific T cell proliferation, IFN gamma secretion and induces specific cytotoxic reactions to CEA(+) colon tumor cells. In addition to T cell response, DCNLGPCEA vaccine generates anti-CEA antibody response, which is principally IgG2a in nature. This antibody participates in cytotoxicity of CEA(+) cells in antibody-dependent manner. This strong anti-CEA cellular and humoral immunity protects mice from tumor development and these mice remained tumor free following second tumor inoculation, indicating generation of effector memory response. Evaluation of underlying mechanism suggests vaccination generates strong CEA specific CTL and antibody response that can completely prevent the tumor growth following adoptive transfer. In support, significant upregulation of CD44 on the surface of lymphocytes from DCNLGPCEA immunized mice was noticed with a substantial reduction in L-selectin (CD62L).

Restoration of dysregulated CC chemokine signaling for monocyte/macrophage chemotaxis in head and neck squamous cell carcinoma patients by neem leaf glycoprotein maximizes tumor cell cytotoxicity

Previous studies have shown that the CC chemokine receptor CCR5 is downregulated on monocyte/macrophage (MO/Mφ) surfaces in head and neck squamous cell carcinoma (HNSCC) patients (stage IIIB). Ligands (RANTES, MIP-1α and MIP-1β) of this chemokine receptor were also secreted in lesser quantity from MO/Mφ of HNSCC patients in comparison with healthy individuals. In an aim to restore this dysregulated receptor–ligand signaling, we have used neem leaf glycoprotein (NLGP), a novel immunomodulator reported from our laboratory. NLGP upregulated CCR5 expression, as evidenced from studies on MO/Mφ of peripheral blood from HNSCC patients as well as healthy individuals. Expression of RANTES, MIP-1α and MIP-1β was also upregulated following NLGP treatment of these cells in vitro. Interestingly, NLGP has little effect on the expression of CCR5 and the ligand RANTES in oral cancer cells. This restored CCR5 receptor–ligand signaling seen in MO/Mφ was reflected in improved CCR5-dependent, p38 mitogen-activated protein kinase (MAPK)-mediated migration of MO/Mφ after NLGP treatment to a standard chemoattractant. NLGP also induces better antigen presentation and simultaneous costimulation to effector T cells by MO/Mφ by upregulating human leucocyte antigen (HLA)-ABC, CD80 and CD86. In addition, NLGP-treated MO/Mφ-primed T cells can effectively lyse tumor cells in vitro. The effects of NLGP on monocyte migration and T cell-mediated oral tumor cell killing were further demonstrated in transwell assays with or without CCR5 neutralization. These results suggest a new approach in cancer immunotherapy by modulating dysregulated CCR5 signals from MO/Mφ.