Phenethyl Isothiocyanate Inhibits In Vivo Growth of Xenograft Tumors of Human Glioblastoma Cells

Abstract

Phenethyl isothiocyanate (PEITC) from cruciferous vegetables can inhibit the growth of various human cancer cells. In previous studies, we determined that PEITC inhibited the in vitro growth of human glioblastoma GBM 8401 cells by inducing apoptosis, inhibiting migration and invasion, and altering gene expression. Nevertheless, there are no further in vivo reports disclosing whether PEITC can suppress the growth of glioblastoma. Therefore, in this study we investigate the anti-tumor effects of PEITC in a xenograft model of glioblastoma in nude mice. Thirty nude mice were inoculated subcutaneously with GBM 8401 cells. Mice with one palpable tumor were divided randomly into three groups: control, PEITC-10, and PEITC-20 groups treated with 0.1% dimethyl sulfoxide (DMSO), and 10 and 20 μmole PEITC/100 μL PBS daily by oral gavage, respectively. PEITC significantly decreased tumor weights and volumes of GBM 8401 cells in mice, but did not affect the total body weights of mice. PEITC diminished the levels of anti-apoptotic proteins MCL-1 (myeloid cell leukemia 1) and XIAP (X-linked inhibitor of apoptosis protein) in GBM 8401 cells. PEITC enhanced the levels of caspase-3 and Bax in GBM 8401 cells. The growth of glioblastoma can be suppressed by the biological properties of PEITC in vivo. These effects might support further investigations into the potential use of PEITC as an anticancer drug for glioblastoma.

Keywords: apoptosis; caspase; glioblastoma; phenethyl isothiocyanate; xenograft.

Figure 1

The effects on body weight in xenograft GBM 8401/luc2 cells-bearing mouse models. The body weights of mice treated with phenethyl isothiocyanate (PEITC) remained similar to those of control mice throughout the study period.

Figure 2

Therapeutic efficacy evaluation of PEITC in xenograft GBM 8401/luc2 cells-bearing mice. (A) The tumor growth of each mouse was monitored by bioluminescent imaging (BLI) every one week. The tumor growth was significantly suppressed by PEITC at both doses (PEITC-10, PEITC-20) compared to the control group. (B) The regions-of-interest (ROIs) of tumors in (A) were quantified. The PEITC-20 group revealed the most obvious tumor inhibition. a¹: p < 0.05, a²: p < 0.01 compared to that of the control; b¹: p < 0.05, b²: p < 0.01 compared to that of PEITC-10 group. (C) The tumor volumes of each mouse were assayed by caliper measurement every 3 days. The tumor volumes were significantly reduced by PEITC at both doses (PEITC-10, PEITC-20 groups) compared to the control group. a¹: p < 0.05, a²: p < 0.01 compared to that of the control; b¹: p < 0.05, b²: p < 0.01 compared to that of PEITC-10 group. (D) Six representative tumor pictures from each group are displayed after the mice were sacrificed. (E) The tumor weights of each mouse were assayed after they were sacrificed on day 21. The tumor weights were significantly decreased by PEITC at both doses (PEITC-10, PEITC-20 groups) compared to the control group. a²: p < 0.01 compared to that of the control; b¹: p < 0.05 compared to that of PEITC-10 group.

Figure 2

Therapeutic efficacy evaluation of PEITC in xenograft GBM 8401/luc2 cells-bearing mice. (A) The tumor growth of each mouse was monitored by bioluminescent imaging (BLI) every one week. The tumor growth was significantly suppressed by PEITC at both doses (PEITC-10, PEITC-20) compared to the control group. (B) The regions-of-interest (ROIs) of tumors in (A) were quantified. The PEITC-20 group revealed the most obvious tumor inhibition. a¹: p < 0.05, a²: p < 0.01 compared to that of the control; b¹: p < 0.05, b²: p < 0.01 compared to that of PEITC-10 group. (C) The tumor volumes of each mouse were assayed by caliper measurement every 3 days. The tumor volumes were significantly reduced by PEITC at both doses (PEITC-10, PEITC-20 groups) compared to the control group. a¹: p < 0.05, a²: p < 0.01 compared to that of the control; b¹: p < 0.05, b²: p < 0.01 compared to that of PEITC-10 group. (D) Six representative tumor pictures from each group are displayed after the mice were sacrificed. (E) The tumor weights of each mouse were assayed after they were sacrificed on day 21. The tumor weights were significantly decreased by PEITC at both doses (PEITC-10, PEITC-20 groups) compared to the control group. a²: p < 0.01 compared to that of the control; b¹: p < 0.05 compared to that of PEITC-10 group.

Figure 3

The effects of PEITC on the expressions of apoptosis-associated proteins in xenograft GBM 8401/luc2 cells-bearing mice. Tumors were isolated from xenograft GBM 8401/luc2 cells-bearing mice after treatment. All samples were analyzed under microscopy at ×100 magnification and photographed. (A) MCL-1 (myeloid cell leukemia 1) and XIAP (X-linked inhibitor of apoptosis protein); (B) Caspase-3 and Bax. (C) Quantification results of MCL-1 and XIAP. (D) Quantification results of Caspase-3 and Bax. a¹: p < 0.05, a²: p < 0.01 compared to that of the control; b¹: p < 0.05, b²: p < 0.01 compared to that of PEITC-10 group.

Figure 4

The effects of PEITC on liver histopathology in GBM 8401/luc2 cells xenograft animal model. Liver tissue from every mouse of every group after treatment was collected and stained with hematoxylin and eosin (H&E). Liver specimens from PEITC-treated and control groups revealed similar structures of hepatocytes and lobular architectures.

Figure 5

Experimental design for the treatments of human GBM 8401-bearing mice. Each mouse was injected with 1 × 10⁷ GBM 8401/luc2 cells. After the tumor volume reached 100–120 mm³, mice were randomized into three different treatment groups (n = 10 per group). PEITC (10, 20 μmole/100 μL PBS) was administered daily by gavage. All mice were sacrificed 21 days after treatments. IHC: immunohistochemical.