RP215 single chain fragment variable and single domain recombinant antibodies induce cell cycle arrest at G0/G1 phase in breast cancer.

BACKGROUND: Targeted therapy is an attractive approach to avoid the side effects of cancer treatment. Based on antibody-targeted superantigens, single chain variable fragment (scFv) and single domain (sdAb) antibodies, characterized by a low molecular weight, low immunogenicity and a high tumor penetration compared to monoclonal antibodies (mAb), have been increasingly used in gene-targeted therapy for cancer. In the present study, we aimed to develop the novel recombinant scFv-RP215 and sdAb-RP215 antibodies based on the variable regions of the RP215 monoclonal antibody (RP215-mAb) against CA215, a pan cancer marker expressed in various human tumor tissues, and to examine their biological activity in breast cancer cell lines.

METHODS: The VH and VL genes were amplified from hybridoma cells secreting RP215-mAb by RT-PCR and joined with a linker using splicing by overlap extension PCR (SOE-PCR) to obtain the RP215-scFv gene, whereas the VH gene was used to generate the RP215-sdAb. Gene fragments of antibodies were subcloned into the pET32a(+) vector and expressed in Escherichia coli BL21. Western blot, indirect immunofluorescence (IF), ELISA and competitive ELISA were used to detect the immunoreactivity of scFv-RP215, sdAb-RP215, and RP215-mAb. The CCK-8 assay and cell cycle analysis were used to assess antibodies function.

RESULTS: The novel recombinant scFv-RP215 and sdAb-RP215 antibodies were successfully developed based on the variable regions of the monoclonal antibody RP215 (RP215-mAb) against CA215. We verified that scFv-RP215 and sdAb-RP215 recognize CA215 on the surface of breast cancer cells (MB231, MCF7, MB468, SK-BR-3 and BT549) and characterized their activity and specificity. Our findings also indicate that scFv-RP215 and sdAb-RP215 induce cell cycle arrest at the G0/G1 phase in breast cancer cells.

CONCLUSION: Our results showed that scFv-RP215 and sdAb-RP215 have excellent immunoreactivity and localize accurately to breast cancer cells in membrane-bound form, suggesting their potential as tumor targeting antibodies for breast cancer therapy.