Dual in vitro invasion/migration suppressing and tamoxifen response modulating effects of a recombinant anti‐ALCAM scFv on breast cancer cells

It has been shown that overexpression of activated leukocyte cell adhesion molecule (ALCAM) is involved in development of resistance to tamoxifen therapy and promotion of cell invasion, migration and metastasis in ER+ breast cancer cells. Thus, we hypothesized that blockade of ALCAM interconnections with antibodies could be an effective approach for reversing mentioned negative events associated with ALCAM overexpression in breast cancer cells. Here, an anti-ALCAM scFv was recombinantly expressed and used throughout study for examination of the putative anticancer effects of ALCAM blockade. The anti-ALCAM scFv coding sequence was obtained from GenBank database and after addition of a 6x His-tag moiety, signal peptide and flanking sequences, the whole construct was expressed in Escherichia coli. Tamoxifen resistant MCF7 cells were then pretreat for 24 hours with purified recombinant anti-ALCAM scFv prior to administration of tamoxifen. In parallel, the cytotoxicity profile of anti-ALCAM scFv and tamoxifen co-treatments against tamoxifen resistant and sensitive MCF7 cell lines was also evaluated using CompuSyn software. The invasion/migration inhibitory effects of anti-ALCAM scFv on MDA-MB-231 cells were also evaluated. Pretreatment with anti-ALCAM scFv could successfully enhance anti-proliferative effects of tamoxifen against resistant MCF-7 cell lines. Furthermore, the combination of 19.2:1 of tamoxifen to anti-ALCAM scFv demonstrated synergistic cell inhibitory effect against tamoxifen resistant MCF7 cell lines. Also, incubating MDA-MB-231 cell lines with anti-ALCAM scFv resulted in a 30% and 25% reduction in number of invaded and migrated cells respectively. Overall, application of anti-ALCAM scFv could significantly suppress cancer cells metastasis in vitro and modulate tamoxifen resistant ER+ MCF7 cell line's sensitivity to tamoxifen. SIGNIFICANCE OF THE STUDY: Acquisition of resistance to tamoxifen therapy is one of the major challenges associated with cancer chemotherapy, gradually turning a responsive tumour into a refractory more invasive one which ultimately ends in disease progression and relapse. Here, we reported expression of an anti-ALCAM scFv, capable of increasing the sensitivity of tamoxifen resistant ER+ MCF-7 cells to tamoxifen therapy following a 24-hour pretreatment period. In addition, we demonstrated that the anti-ALCAM scFv monotherapy was also capable of suppressing invasion and migration of MDA-MB-231 cells in Boyden chamber assays.