Antineoplastic agents in chemotherapy facilitating tumor growth and angiogenesis in the interval administrations.

ABSTRACT

AIMS: There is emerging evidence that antineoplastic agents and the cytotoxic effects on tumor tissues attenuate the benefits of chemotherapy due to tumor microenvironment changes. Nevertheless, the actual relationship between chemotherapy and recurrent tumors in which the genotypes differ from the original tumor after chemotherapy is unclear. MATERIALS AND METHODS: Bone marrow transplantation, flow cytometer, immune inhibition and immunofluorescence will be utilized to investigate the effect of antineoplastic agents on bone-marrow-derived cells (BMDCs) release and recruitment, and to explore the pathways and mechanisms of antineoplastic agents in promoting tumor growth. KEY FINDINGS: Tumor growth and angiogenesis were significantly enhanced in the mouse model after treatment with antineoplastic agents such as cyclophosphamide, 5-fluorouracil, or cisplatin, along with large increases in proangiogenic vascular endothelial growth factor receptor-2 (VEGFR2+), ß3+, CD11b+Gr-1+, and VEGFR2+ß3+ BMDCs in circulating blood. BMDC recruitment and VEGFR2 and ß3 mRNA transcription in tumor tissues were also enhanced by antineoplastic agents. Antineoplastic-agent-treated BMDCs markedly augmented tumor and endothelial cell proliferation, and ß3 mRNA transcription in endothelial cells (ECs). SIGNIFICANCE: The results suggested that antineoplastic-agent treatment augmented the tumor microenvironment by mobilizing proangiogenic BMDCs, enhancing BMDC recruitment and angiogenesis, and increasing BMDC-mediated tumor and EC functions. These results led to tumor growth and angiogenesis aggravation. It is paramount to elucidate the potential mechanism by which the cellular and molecular effects triggered by the antineoplastic agents attenuate the effects of cancer therapy, and thereafter to explore possible methods for improving tumor treatment efficacy.