CXCR4 expression enhances CXCL12 induced invasion, while CXCR7 expression impairs it. (a) In vitro invasion of MTLn3 JP, MTLn3 CXCR4, MTLn3 CXCR7, and MTLn3 CXCR4-CXCR7 cells in the presence or absence of 10 nM CXCL12. The total number of invasive cells present per filter were counted and normalized to the invasive response of control MTLn3 JP cells in the absence of CXCL12 stimulation (n = 3 individual experiments per condition). (b) In vivo invasion of MTLn3 JP, MTLn3 CXCR4, MTLn3 CXCR7, and MTLn3 CXCR4-CXCR7 primary tumors in response to the indicated concentrations of CXCL12. Cells were allowed to invade for four hours into needles containing Matrigel plus or minus chemoattractant. Note that the buffer measurements for all transductants are plotted and overlap. For the MTLn3 CXCR7 transductant, there is no measurement at 6.25 nM CXCL12 as there were no responses at higher concentrations of CXCL12 and the chemotaxis data showed no response at low concentration of CXCL12. Data are from 10 mice with three to eight needles per condition for MTLn3 JP, 14 mice with 5 to 10 needles per condition for MTLn3 CXCR4, eight mice with three to six needles per condition for MTLn3 CXCR7, 13 mice with three to eight needles per condition for MTLn3 CXCR4-CXCR7. Comparison of MTLn3 CXCR7 invasion to CXCL12 with that of MTLn3 JP cells show statistically significant reduction at 31.25 nM (P < 0.05) and 62.5 nM (P < 0.005) using t-test. Comparison between MTLn3 CXCR4 and MTLn3 JP invasion shows statistically significant differences at 6.25 nM, 15.6 nM and 31.25 nM CXCL12 with P < 0.05, P < 0.005, and P < 0.05, respectively. MTLn3 CXCR4-CXCR7 tumors showed statistically significant decreased invasion at all concentrations of CXCL12 tested compared to MTLn3 CXCR4 6.25 nM P < 0.05, 15.6 nM P < 0.005, 31.25 nM P < 0.005, 62.5 nM P < 0.05. (c) In vivo invasion of MTLn3 CXCR4-CXCR7 tumors in response to 15.6 nM CXCL12 with or without 100 nM AMD3100. Three animals were tested with three to seven needles counted per condition. (d) Matrix degradation of MTLn3 CXCR4 and MTLn3 CXCR4-CXCR7 cells in the absence or presence of 5 nM CXCL12 (at least 19 fields were counted per condition). Means and SEMs are shown. P < 0.05 is represented by * as determined by t-test.