Therapy with transcutaneous administration of imiquimod combined with oral administration of sorafenib suppresses renal cell carcinoma growing in an orthotopic mouse model

Transcutaneous Imiquimod Combined With Anti-Programmed Cell Death-1 Monoclonal Antibody Extends the Survival of Mice Bearing Renal Cell Carcinoma

PURPOSE

Imiquimod (IQM), an imidazoquinoline derivative, is an immunomodulator that activates an adaptive immune response. IQM is applied topically for genital warts and actinic keratosis. Programmed cell death-1 (PD-1) suppresses activated T cells by binding to programmed cell death-ligand 1 and programmed cell death-ligand 2, braking antitumor immunity. Anti-PD-1 therapy has been used for various malignant neoplasms including renal cell carcinoma (RCC). Whether combination therapy with transcutaneous administration of IQM cream and intraperitoneal administration of anti-PD-1 monoclonal antibody (mAb) suppresses mouse RCC cells growing in subcutaneous tissue was investigated.

METHODS

Female BALB/c mice were implanted subcutaneously with 2 × 105 RENCA mouse RCC cells and treated with a transcutaneously applied cream containing IQM and intraperitoneal administration of anti-PD-1 mAb beginning 5 days after cell implantation. Tumor burden and survival of the mice were determined. RENCA tumor-specific IgG production and a minor CD8+ T cell subset derived from the spleen of the mice bearing RENCA tumor were detected by flow cytometry. The tumor and spleen weights of mice treated with IQM, anti-PD-1 mAb, and their combination were compared.

RESULTS

Combination therapy with IQM and anti-PD-1 mAb significantly suppressed tumor growth compared to each monotherapy and prolonged the survival of the mice. The combination therapy produced more RENCA tumor-specific IgG than either IQM or anti-PD-1 mAb alone. The percentage of the CD44highCD62Llow CD8+ T cell subset (effector memory T cells) among splenocytes from mice treated with IQM therapy increased. The CD44lowCD62Llow CD8+ T cell subset (pre-effector-like T cells) of mice treated with anti-PD-1 mAb increased. A negative correlation between tumor and spleen weights was suggested in mice treated with therapies containing IQM.

CONCLUSIONS

The present results show that combination therapy with IQM and anti-PD-1 mAb might be a promising novel therapeutic strategy for advanced RCC.

Normalization of tumor vasculature by imiquimod: proposal for a new anticancer therapeutic indication for a TLR7 agonist

Imiquimod (IMQ), a drug from aminoquinoline group, is the toll-like receptor 7 (TLR7) agonist. It acts as an immunostimulant and radio-sensitizing agent. IMQ stimulates both innate and adaptive immune response. Despite studies conducted, there are no unambiguous data showing how IMQ affects the condition of tumor blood vessels. Tumor vasculature plays the main role in tumor progression. Formation of abnormal blood vessels increases area of hypoxia which recruits suppressor cells, blocks tumor infiltration by CD8+ T lymphocytes, inhibits efficacy of chemoterapeutic drug and leads to cancer relapse. Normalization is a type of therapy targeted at abnormal tumor blood vessels. Here, we demonstrated that 50 µg of IMQ inhibits the growth of melanoma tumors more efficiently, compared to other tested doses and the control group. Dose escalation did not improve the therapeutic antitumor potential of TLR7 agonist. A dose of 50 µg of IMQ most effectively reduced tumor blood vessel density. Imiquimod normalized tumor vasculature both structurally (by reducing vessel tortuosity and increasing pericyte coverage) and functionally (by improving tumor perfusion) in a dose-dependent manner. Hypoxia regions in tumors of treated mice were significantly reduced after IMQ administration. A dose of 50 µg of IMQ had also the greatest impact on the changes in tumor-infiltrating T lymphocytes levels. TLR7 agonist inhibited angiogenesis in treated mice. Functional vascular normalization by IMQ increases the effectiveness of low dose of doxorubicin. Higher dose of IMQ showed worse effects than lower doses including decreased tumor perfusion, increased tumor hypoxia and immunosuppression. This knowledge may help to optimize the combination of the selected IMQ dose with e.g. chemotherapy or radiotherapy to elicit synergistic effect in cancer treatment. To conclude, we outline IMQ repurposing as a vascular normalizing agent. Our research results may contribute to expanding the therapeutic indications for the use of IMQ in anticancer therapy in the future.

Recent advances in cancer immunotherapy: Modulation of tumor microenvironment by Toll-like receptor ligands

Immunotherapy is considered a promising approach for cancer treatment. An important strategy for cancer immunotherapy is the use of cancer vaccines, which have been widely used for cancer treatment. Despite the great potential of cancer vaccines for cancer treatment, their therapeutic effects in clinical settings have been limited. The main reason behind the lack of significant therapeutic outcomes for cancer vaccines is believed to be the immunosuppressive tumor microenvironment (TME). The TME counteracts the therapeutic effects of immunotherapy and provides a favorable environment for tumor growth and progression. Therefore, overcoming the immunosuppressive TME can potentially augment the therapeutic effects of cancer immunotherapy in general and therapeutic cancer vaccines in particular. Among the strategies developed for overcoming immunosuppression in TME, the use of toll-like receptor (TLR) agonists has been suggested as a promising approach to reverse immunosuppression. In this paper, we will review the application of the four most widely studied TLR agonists including agonists of TLR3, 4, 7, and 9 in cancer immunotherapy.