AIM:To examine the expression of downstream of tyrosine kinase(DOK)1-6 genes in normal and breast cancer tissue and correlated this with several clinicopathological and prognostic factors.METHODS:DOK1-6 m RNA extraction and reverse transcription were performed on fresh frozen breast cancer tissue samples(n = 112) and normal background breast tissue(n = 31). Tissues were collected between 1991 and 1996 at two centres and all patients underwent mastectomy and ipsilateral axillary node dissection. All tissues were randomly numbered and the details were only made known after all analyses were completed. Transcript levels of expression were determined using real-time polymerase chain reaction and analyzed against TNM stage, tumour grade and clinical outcome over a 10-year follow-up period.RESULTS:DOK-2 and DOK-6 expression decreased with increasing TNM stage. DOK-6 expression decreased with increasing Nottingham Prognostic Index(NPI) [NPI-1 vs NPI-3(mean copy number 15.4 vs 0.22, 95%CI:2.7-27.6, P = 0.018) and NPI-2 vs NPI-3(mean copy number 7.6 vs 0.22, 95%CI:0.1-14.6, P = 0.048)]. After a median follow up period of 10 years, higherlevels of DOK-2 expression were found among patients who remained disease-free compared to those who developed local or distant recurrence(mean copy number 3.94 vs 0.0000096, 95%CI:1.0-6.85, P = 0.0091), and distant recurrence(mean copy number 3.94 vs 0.0025, 95%CI:1.0-6.84, P = 0.0092). Patients who remained disease-free had higher levels of DOK-6 expression compared to those who died from breast cancer.CONCLUSION:Decreasing expression levels of DOK-2 and DOK-6 with increased breast tumour progression supports the notion that DOK-2 and DOK-6 behave as tumour suppressors in human breast cancer. AIM: To examine the expression of downstream of tyrosine kinase (DOK) 1-6 genes in normal and breast cancer tissue and correlated with several clinicopathological and prognostic factors. METHODS: DOK 1-6 m RNA extraction and reverse transcription were performed on fresh frozen Tissues were collected between 1991 and 1996 at two centers and all patients underwent mastectomy and ipsilateral axillary node dissection. All tissues were randomly numbered and the details were only made known after all analyzes were completed. Transcript levels of expression were determined using real-time polymerase chain reaction and analyzed against TNM stage, tumor grade and clinical outcome over a 10-year follow-up period .RESULTS: DOK-2 and DOK -6 expression decreased with increasing TNM stage. DOK-6 expression decreased with increasing Nottingham Prognostic Index (NPI) [NPI-1 vs NPI-3 (mean copy number 15.4 vs 0.22, 95% CI: 27.6, P = 0.018) and NPI-2 vs NPI-3 (mean copy number 7.6 vs. 0.22, 95% CI: 0.1-14.6, P = 0.048)]. After a median follow up period of 10 years, higher levels of DOK- 2 expression were found among patients who remained disease-free compared to those who developed local or distant recurrence (mean copy number 3.94 vs 0.0000096, 95% CI: 1.0-6.85, P = 0.0091), and distant recurrence (mean copy number 3.94 vs 0.0025, 95% CI: 1.0-6.84, P = 0.0092). Patients who remained disease-free had higher levels of DOK-6 expression compared to those who died from breast cancer. CONCLUSION: Decreasing expression levels of DOK-2 and DOK- 6 with increased breast tumor progression supports the not that that DOK-2 and DOK-6 behave as tumor suppressors in human breast cancer.