Preclinical evaluation of recombinant herpes simplex virus oHSV2 in colorectal cancer / 中国肿瘤临床

ABSTRACT

Objective:To investigate therapeutic efficacy and mechanisms of action of oncolytic agent derived from herpes simplex virus type 2 (oHSV2) in a xenograft mouse model bearing CT26 colorectal cancer. Methods:BALB/c mice were subcutaneously inoculated with CT26 cells to establish a xenograft mouse model of colorectal cancer. 1) After intratumoral administration of oHSV2, enzyme-linked im-munosorbent assay was used to determine granulocyte-macrophage colony-stimulating factor (GM-CSF) expression levels in the blood. 2) Model mice were divided into three groups:PBS group (negative control), oHSV2 group, and 5-fluorouracil (5-FU) group (positive control). After drug administration, drug effectiveness was evaluated on the basis of weight, tumor volume, general state, and survival time. 3) Cells from the draining lymph nodes (TDLN) and tumor were surgical y removed and used to quantify mature dendritic cel s (DCs) and T lym-phocytes by flow cytometry. Result:1) In the CT26 xenograft model, level of GM-CSF continuously elevated. At day 8, peak value was attained in the blood at concentration of 3150±327.1 pg/mL. Then, GM-CSF expression gradually reduced as time progressed. 2) In in vivo study, both oHSV2 and 5-FU exerted antitumor effects relative to PBS group (50 days vs. 36 days, P0.05). Skin of virus injection region did not present necrosis and ulceration. 3) In the TDLN, the frequency of DC was increased when treated with oHSV2 compared with the control group (6.49%vs. 3.73%, P<0.01). Similarly, the percentage of CD4+and CD8+T-cel s from the oHSV2-treated group was signifcantly higher than mock-treated tumors (15%vs. 8.57%, P<0.01;8.19%vs. 5.15%, P<0.01). However, number of cells in the 5-FU group were significantly reduced with respect to that of the negative group (al P<0.01). Conclusion:oHSV2 exerted potent antitumor effects in a murine colorectal cancer model. Compared with 5-FU, oHSV2 treatment caused fewer side effects. Such antitumor effect may be induced by stimulation of immune activity by GM-CSF production.