Figure 6

Focal adhesion kinase (FAK) mediates tumor cell autonomous-driven metastasis and systemically driven mammary tumor growth. (a) Control (i.e., scram) and FAK-deficient (shFAK) 4T1 cells were engrafted onto the mammary fat pads of 6-week-old Balb/C mice. Data are expressed as the mean (± SEM) tumor volumes (n = 5) measured at the indicated time points after engraftment. (b) FAK-deficient 4T1 tumors displayed significantly decreased pulmonary metastasis. Data are the mean (± SEM) pulmonary area flux units detected in Balb/C mice (n = 5) imaged at the indicated time points after engraftment (*P < 0.05). Shown are representative mice engrafted with control (i.e., scram) and FAK-deficient (shFAK) 4T1 cells (inset). (c) Immunostaining primary tumor sections with phospho-specific antibodies against p38 MAPK (p-p38) or Smad2 (p-smad2) showed intense nuclear localization of phosphorylated p38 MAPK at the invasive front of control (i.e., scram) tumors (black arrows). Tumors derived from FAK-deficient 4T1 cells exhibit significantly reduced phosphorylation and nuclear accumulation of p38 MAPK (black arrows). Similarly, abundant phosphorylation of Smad2 (p-smad2) was readily detected near the invasive front of control (i.e., scram) 4T1 tumors (right of the line), but not in tumors arising from their FAK-deficient (shFAK) counterparts. (d) 4T1 cells were engrafted onto the mammary fat pads of 6-week-old Balb/C mice. One week after engraftment, the mice were left untreated (NS) or treated with the FAK inhibitor PF-562271 (PF-271; 50 mg/kg/day) for the duration of the experiment. Data are expressed as the mean (± SEM) tumor volumes (n = 5) measured at the indicated time points after engraftment (*P < 0.05; **P < 0.005). (e) Mice treated with PF-562271 as in panel (d) displayed significantly decreased pulmonary metastasis. Data are expressed as the mean (± SEM) pulmonary area flux units detected in Balb/C mice (n = 5) imaged at the indicated time points after engraftment (**P < 0.005). Shown are representative untreated (NS) or PF-562271 (PF-271)-treated mice (inset). (f) Control (NS) 4T1 mammary fat-pad tumors displayed a high degree of macrophage infiltration, as demonstrated by immunostaining for the F4/80 antigen. Macrophage infiltration was greatly reduced in tumor-bearing mice treated with PF-562271 (PF-271).