New therapeutic strategies are required to enhance the anticancer efficacy of chemotherapeutic drugs and to reduce their cytotoxicity. The purpose of this study was to assess the anti-tumor, antimetastatic and anti-apoptotic activities of sinapic acid (SA) and 3,3′-diindolylmethane (DIM) in solid Ehrlich carcinoma (SEC) induced in mice and combining SA or DIM compounds with cyclophosphamide (CYP).

For induction of solid tumor, the right hind limbs of mice were inoculated subcutaneously with Ehrlich carcinoma cells. After 5 days of tumor inoculation, mice were treated with SA (56 mg/kg), DIM (40 mg/kg), CYP (10 mg/kg), and their combinations (SA/CYP) and (SA/DIM) for 21 days. The mRNA levels of Elabela, Serpina3, caspase-3, MMP-2 and MMP-9 were assessed by qPCR. Tumor and liver tissues were stained with hematoxylin and eosin for histological examination. Serum was investigated for ALT and AST activities.

Treatment of SEC mice with SA and DIM significantly reduced solid tumor weight by 45.6% and 33.2%, respectively. They also reduced tumor size and increased life span of SEC mice. SA and DIM diminished area of metastatic nodules of tumor cells in the liver by 54.1% and 47.4%, respectively. They also reduced serum aminotransferases activities. Both SA and DIM were found to upregulate caspase 3 and downregulate MMP-2 and MMP-9. Furthermore, SA and DIM reduced gene expression of Elabela by (44.8% and 35.1%) and Serpina3 by (30.7% and 23.5%), respectively. SA and DIM were also shown to potentiate the anti-tumor activity CYP.

SA and DIM showed promising antitumor effects and enhanced CYP antitumor activity mostly through upregulation of apoptotic caspase 3 and suppressing metastatic enzymes MMP-2 and MMP-9. Additionally, SA and DIM exhibited a hepatoprotective effect. Our results suggest that these natural compounds may be used to improve the efficacy and reduce the adverse effects of chemotherapeutic drugs in the treatment of solid malignancies.