CXCR4 and medullary thyroid gland carcinoma: However, the increases in colony number and the number of cells in S phases, plus the reduction in percentage of apoptotic cells, were reversed when cells were co-transfected with miR-455-5p inhibitor and shCXCL12 or when miR-455-5p inhibitor-transfected MTC cells were treated with AMD3100, the CXCR4 antagonist (Fig. 3b-f).