The Roles of Macrophages and Nitric Oxide in Interleukin-3-Enhanced HSV-Sr39tk-Mediated Prodrug Therapy

Abstract

The herpes simplex virus thymidine kinase/ganciclovir (HSV-sr39tk/GCV) system is a well-established prodrug system used in cancer gene therapy. However, this system is currently not effective enough to eradicate malignant tumors completely. This study aimed to evaluate whether co-expression of interleukin-3 (IL-3) could enhance the anti-tumor activity of HSV-sr39tk/GCV prodrug gene therapy using a murine TRAMP-C1 prostate tumor model. In vitro results demonstrated that HSV-sr39tk-transfected cells exhibited enhanced sensitivity to the GCV prodrug, which was not affected by co-expression of the mIL-3 gene. However, in vivo studies showed that co-expression of the mIL-3 gene significantly increased the HSV-sr39tk/GCV-induced tumor growth delay and even cured the tumor. The TRAMP-C1-specific immune response of spleen lymphocytes from mice bearing HSV-sr39tk- and IL-3-expressing TRAMP-C1 tumors was measured by ELISA. Results showed that IL-3-activated IL-4-dominant lymphocytes became IFN-γ- dominant lymphocytes after combined HSV-sr39tk/GCV therapy. The efficacy of combined therapies on tumor regression was reduced when macrophages populations were depleted by carrageenan or NO production was inhibited by administration of the iNOS inhibitor, L-NAME. These results suggest that utilizing a bicistronic vector to express HSV-sr39tk and the IL-3 gene induced an enhanced macrophage- or NO-dependent anti-tumor effect.

Characterization of macrophage - cancer cell crosstalk in estrogen receptor positive and triple-negative breast cancer

“…IL-3 can also activate macrophages to increase the expression of MHC class II molecules and IL-1 37 . The use of IL-3 has also been reported to enhance macrophage-dependent anti-tumor effects when utilized in combination with cancer gene therapy 38 .…”

Nitric oxide inhibits the transcription of E6 gene of human papillomavirus

“…Other accessory factors such as NO are involved in the progression of infected cells to full neoplastic phenotype. NO can inhibit the replication of a variety of viruses, such as murine poxvirus and herpes viruses including HSV and Epstein-Barr virus (EBV), and RNA viruses including coxsackievirus (Yu et al, 2013;Gao, et al, 1999;Akaike and Maeda, 2000). In this study we found that in SiHa cells with integrated HPV, NO caused dose and time dependent inhibition of the expression of HPV early gene E6 mRNA, indicating that NO inhibits the replication of HPV.…”

Distinct Role of CD11b+Ly6G−Ly6C− Myeloid-Derived Cells on the Progression of the Primary Tumor and Therapy-Associated Recurrent Brain Tumor

“…The HSV-sr39tk suicide gene constructed by Dr. Ching-Fang Yu [37] was transfected into ALTS1C1 by Effectene Transfection Reagent (QIAGEN, 1054250, Mainz, Germany). Briefly, 1 µg of plasmid DNA diluted to a total of 150 µL and mixed with 8 µL Enhancer and kept at room temperature for 4 min.…”

“…Even local radiation therapy (RT) in this model stimulates myelopoiesis and modifies the tumor microenvironment in favor of anti-inflammatory M2 TAMs, which promote tumor recurrence [39]. Interestingly, in another model of tk/GCV gene therapy combined with IL-3 immune therapy in a prostate tumor model, M1 macrophages were generated that had anti-tumor efficacy with NO production [37]. Our aim here was to specify the roles of CD11b + Gr-1 − myeloid cells in ALTS1C1 tumors following chemotherapy.…”

“…HSV-tk is 1000 times more efficient than the mammalian thymidine kinase to use monophosphorylate GCV (thymidine analog to inhibit DNA synthesis) as a substrate. By expressing HSV-tk in the cancerous cells, selective cytotoxicity against tumor cells is therefore achieved [37]. These genetic targeting methods allowed us to investigate the role of the CD11b + Gr-1 − myeloid cells in brain tumor progression and recurrence after pro-drug GCV chemotherapy in our established astrocytoma model.…”