CXCR4 and cancer: Upregulated BCL-6 promotes the immortalization of mouse embryonic fibroblasts and primary B cells by elevating cyclin D1 levels.257 HIF-1α binds CXC chemokine receptor type 4 (CXCR4) to promote B-cell viability.258 The immune effects of B cells on cancers have not been conclusively established.