Enhancement of therapeutic DNA vaccine potency by melatonin through inhibiting VEGF expression and induction of antitumor immunity mediated by CD8+ T cells

Abstract

To be effective, therapeutic cancer vaccines should stimulate both an effective cell-mediated and a robust cytotoxic CD8+ T-cell response against human papillomavirus (HPV)-infected cells to treat the pre-existing tumors and prevent potential future tumors. In this study, the therapeutic experiments were designed in order to evaluate antitumor effect against the syngeneic TC-1 tumor model. The anti-tumor efficacy of a HPV-16 E7 DNA vaccine adjuvanted with melatonin (MLT) was evaluated in a C57BL/6 mouse tumor model by measuring tumor growth post vaccination and the survival rate of tumor-bearing mice, analyzing the specific lymphocyte proliferation responses in control and vaccinated mice by MTT assay. The E7-specific cytotoxic T cells (CTL) were analyzed by lymphocyte proliferation and lactate dehydrogenates (LDH) release assays. IFN-γ, IL-4 and TNF-α secretion in splenocyte cultures as well as vascular endothelial growth factor (VEGF) and IL-10 in the tumor microenvironment were assayed by ELISA. Our results demonstrated that subcutaneous administration of C57BL/6 mice with a DNA vaccine adjuvanted with MLT dose-dependently and significantly induced strong HPV16 E7-specific CD8+ cytotoxicity and IFN-γ and TNF-α responses capable of reducing HPV-16 E7-expressing tumor volume. A significantly higher level of E7-specific T-cell proliferation was also found in the adjuvanted vaccine group. Furthermore, tumor growth was significantly inhibited when the DNA vaccine was combined with MLT and the survival time of TC-1 tumor bearing mice was also significantly prolonged. In vivo studies further demonstrated that MLT decreased the accumulation of IL-10 and VEGF in the tumor microenvironment of vaccinated mice. These data indicate that melatonin as an adjuvant augmented the cancer vaccine efficiency against HPV-associated tumors in a dose dependent manner.

Heparanase, cell signaling, and viral infections

“…Upregulation of VEGF during an ocular HSV-1 infection can lead to corneal neovascularization, and elevated VEGF levels during DENV infections contribute to dengue hemorrhagic fever [71,72]. Inhibiting VEGF reduces the severity of viral infection and tumor growth [73][74][75].…”

<p>Cervical Cancer: Emerging Immune Landscape and Treatment</p>

“…All of these vaccines types exerted antitumor effects through activating the T cell response, especially CD8+ cells. [106][107][108] In addition, increased level of IFN-γ helped mediate cellular immunity. 109 Scientists prefer to combine therapeutic vaccines and immune checkpoint inhibitors such as PL-L1 and CTLA-4 in trials.…”

Antigens from H22 cell mutation induced by lentinan are correlated with HCC immunoprophylaxis

“…The T lymphocyte transformation test and B lymphocyte transformation experiment were carried out according to the instructions of the kit(American Biolegend Co., Ltd.). With the results were tested at 570nm, the stimulation index was calculated to judge the proliferation rate of T lymphocytes and B lymphocytes [19]. The stimulation index is according to the following formula.…”