Activated Src increases adhesion, survival and alpha2-integrin expression in human breast cancer cells.

Focal adhesion kinase (FAK) is an intracellular kinase that localizes to focal adhesions. FAK is overexpressed in human tumours, and FAK regulates both cellular adhesion and anti-apoptotic survival signalling. Disruption of FAK function by overexpression of the FAK C-terminal domain [FAK-CD, analogous to the FRNK (FAK-related non-kinase) protein] leads to loss of adhesion and apoptosis in tumour cells. We have shown that overexpression of an activated form of the Src tyrosine kinase suppressed the loss of adhesion induced by dominant-negative; adenoviral FAK-CD and decreased the apoptotic response in BT474 and MCF-7 breast cancer cell lines. This adhesion-dependent apoptosis was increased by the Src-family kinase inhibitor PP2 [4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine]. We have also shown that expression of activated Src in breast cancer cells increased the expression of alpha2-integrin and that overexpression of alpha2-integrin suppressed FAK-CD-mediated loss of adhesion. Our results suggest a model in which Src regulates adhesion and survival through enhanced expression of the alpha2-integrin. This provides a mechanism through which Src promotes cellular adhesion and alters the adhesive function of FAK.

Clinical significance of bone marrow micrometastasis detected by nested rt-PCR for keratin-19 in breast cancer patients.

PURPOSE: Breast cancers in the early phase frequently undergo distant metastasis and survival of patients is greatly dependent on distant metastasis. The occurrence of micrometastasis has been suggested to relate with prognostic features of breast cancer, such as lymph node metastasis and the presence of vascular invasion. The aim of this study was to examine the presence of keratin-19 mRNA of epithelial tumors in bone marrow aspirates obtained from breast cancer patients and its possible correlation with tumor staging and disease-free survival. METHODS: Bone marrow samples were obtained from 59 breast cancer patients at the time of surgery. We separated the mononuclear fraction from the samples and carried out nested reverse transcriptase polymerase chain reaction (RT-PCR) for the detection of keratin-19 mRNA with two different pairs of primers. After operation, the patients were followed up at 3-month intervals. We studied the possible correlation of the detection of keratin-19 mRNA with tumor size, nodal involvement, stage and recurrence rate. RESULTS: Bone marrow micrometastasis was detected by nested RT-PCR for keratin-19 mRNA in one of four patients with ductal carcinoma in situ (DCIS), 13 of 30 patients with T1, 11 of 20 patients with T2 and all four patients with T3 lesion. Recurrence was observed in seven cases and all of them were positive for micrometastasis in bone marrow. CONCLUSION: The method of nested RT-PCR to detect the presence of keratin-19 mRNA in bone marrow from patients with breast cancer is sensitive and reliable. Moreover, early recurrence was observed in the patients with the tumor mRNA detected in bone marrow. Additional studies with larger numbers of patients and longer follow-up are desirable.