A therapeutic DNA vaccine and gemcitabine act synergistically to eradicate HPV-associated tumors in a preclinical model

Abstract

Although active immunotherapies are effective strategies to induce activation of CD8 + T cells, advanced stage tumors require further improvements for efficient control. Concerning the burden of cancer-related to Human papillomavirus (HPV), particularly the high incidence and mortality of cervical cancer, our group developed an approach based on a DNA vaccine targeting the HPV-16 E7 oncoprotein (pgDE7h). This immunotherapy is capable of inducing an antitumour CD8 + T cell response but show only partial control of tumors in more advanced growth stages. Here, we combined a chemotherapeutic agent (gemcitabine-Gem) with pgDE7h to overcome immunosuppression and improve antitumour responses in a preclinical mouse tumor model. Our results demonstrated that administration of Gem had synergistic antitumor effects when combined with pgDE7h leading to eradication of both early-stages and established tumors. Overall, the antiproliferative effects of Gem observed in vitro and in vivo provided an optimal window for immunotherapy. In addition, the enhanced antitumour responses induced by the combined therapeutic regimen included enhanced frequencies of antigen-presenting cells (APCs), E7-specific IFN-γ-producing CD8 + T cells, and cytotoxic CD8 + T cells and, concomitantly, less pronounced accumulation of immunosuppressive myeloid-derived suppressor cells (MDSCs) and regulatory T cells (Tregs). These findings demonstrated that the combination of Gem and an active immunotherapy strategy show increased effectiveness, leading to a reduced need for multiple drug doses and, therefore, decreased deleterious side effects avoiding resistance and tumor relapses. Altogether, our results provide evidence for a new and feasible chemoimmunotherapeutic strategy that supports future clinical translation.

Single immunizations of self-amplifying or non-replicating mRNA-LNP vaccines control HPV-associated tumors in mice

“…Therefore, gD may act as a checkpoint molecule and, once fused to the E7 oncoprotein, enhances the antitumor activity of activated CD8 + T cells. Unlike purified protein or DNA gDE7-based vaccines, which require cotreatment with chemotherapies ( 57 , 58 ), electroporation ( 44 ), adjuvants ( 37 , 39 , 42 , 59 , 60 ), blockers of immunosuppressive mechanisms ( 43 , 61 , 62 ), or prime-boost immunizations to induce efficient control of established tumors ( 37 , 43 , 58 ), the mRNA-LNP formulations tested in this study induced potent antitumor protection in mice immunized with a single low dose without additional combined treatment.…”

“…Moreover, we found that gDE7 mRNA-LNP vaccine–induced antitumor protection was also partially affected in mice deficient for CD4 + T cell responses, demonstrating that CD8 + T cells are induced through CD4 T cell–dependent and T cell–independent mechanisms in this tumor model. It is well known that the protective responses in the TC-1 tumor model are mediated by CD8 + T cells ( 42 , 58 , 71 ). It was also demonstrated that CD4 + T cells contribute to the efficient priming of CD8 + T cells and to the development of long-lived immune memory ( 72 , 73 ).…”

Current progress in the development of prophylactic and therapeutic vaccines

“…Another DNA-based vaccine pgDE7h (encoding HPV16 E7 fused to the herpes simplex virus type 1 (HSV-1) glycoprotein D (gD)) was found to have a synergistic antitumor effect when combined with Gemcitabine (Gem), a nucleoside analogue used in the clinic for a wide range of tumors. This combination induced tumor-specific cytotoxic CD8+ T cells and eradicated existing tumors (Ramos da Silva et al, 2021). In addition, one study found that pembrolizumab combined with the GX-188E (a DNA-based vaccine engineered to express E6 and E7 proteins of HPV16 and HPV18 fused to extracellular domain of Flt3L and the signa sequence of tissue plasminogen activator) offers a new possible regimen for CIN3 patients (Choi et al, 2020).…”

Therapeutic vaccines for human papillomavirus-related cancer: progress and challenges

“…These vaccines are based on the production of a hybrid protein formed by the fusion of Herpes simplex virus-1 (HSV-1) glycoprotein Editorial Therapeutic vaccines for human papillomavirus-related cancer: progress and challenges D (gD) and the HPV 16 E7 oncoprotein (gDE7), which activate CD8 + E7-specific T cells and elicit a significant antitumor response in mice models. When combined with other techniques such as electroporation (10), IDO inhibitors (9), melatonin (9), polyinosinic:polycytidylic acid [poly(I:C)] (20), spores (11), chemotherapies (7,8), and IL-10 inhibitors (21), the antitumor potential of gDE7-based vaccines was boosted.…”

“…In the field of therapeutic vaccines, the focus of HPV research relies on strategies that deliver HPV oncoproteins to target immune cells ( 5 - 7 ), eliciting an antitumor response capable of controlling tumor development and achieving partial or total tumor remission. Furthermore, treatment combinations are required to boost the antitumor potential of a vaccine candidate ( 8 - 11 ). In this proposal, Lee et al [2022] design vaccines based on HPV-16 E7 short or long peptides and tested different treatment approaches in a tumor-mouse model ( 12 ).…”