Depletion of CXCR7 causes cell cycle arrest, but not apoptosis. wt-MCF7, MCF7-LTED, wt-SUM44 and SUM44-LTED cells were transfected with sicontrol or siCXCR7 × oestradiol (E2) for 72-hours. (A) Whole-cell extracts were immunoblotted and assessed for changes in expression of BCL2, cleaved poly(ADP-ribose) polymerase (PARP) and β-arrestins 1 and 2. (B) Changes in BCL2 were assessed by quantitative RT-PCR. Data are expressed relative to dextran-coated charcoal (DCC)–treated sicontrol. (C) Assessment of alteration in S- and G1-phase accumulation as a result of CXCR7 depletion. Data are expressed as mean × SEM. *P <0.05, **P <0.01, ***P <0.001. (D) Immunoblot analysis of cell cycle markers in response to CXCR7 depletion. Data shown are representative of a minimum of three independent experiments. CXCR, C-X-C chemokine receptor; LTED, Long-term oestrogen deprivation; si, Small interfering; wt, Wild type.