STAT3, HIF-1alpha, EPO and EPOR - signaling proteins in human primary ductal breast cancers

STAT3 upregulates expression of HIF-1 induced EPO. Receptor EPOR was reported to activate STAT3. Our study was aimed at demonstration of tissue immunoreactivities of those proteins and determination of their relationships in reference to clinicopathological variables of breast cancers. We detected STAT3, HIF-1alpha, EPO and EPOR in specimens of 76 human, female, ductal breast cancers by immunohistochemistry. STAT3 was detected in 38 of 76 cancers (50%). HIF-1alpha was found in 55 cases (72%). EPO positive tumors comprised 89% of all the cancers (68 cases). EPOR was also visualized in 55 cases (72%). Anti-HIF-1alpha and anti-STAT3 stained nuclei and cytoplasm of breast cancer cells in diffuse and finely granular fashion. Strong membranous expressions of EPO and EPOR were distributed in cytoplasmic and membranous granularity or diffuse staining. STAT3 correlated with HIF-1 in general (r=0.4012, p<0.0001) and in different patients' subgroups. STAT3 was significantly associated with EPO and EPOR in all the cancers (r=0.2370, p=0.039 and r=0.3336, p=0.003, respectively). Besides a correlation between STAT3 and EPOR in node negative ones, STAT3 wasn't related to EPO and EPOR in remaining subgroups. HIF-1alpha correlated with EPO and EPOR in most of analyzed groups. Immunoreactivity to EPO generally was associated with EPOR (r=0.3520, p=0.002). Statistically analyzed distributions of the proteins reflected functional dependences among STAT3, HIF-1alpha, EPO and EPOR in cellular signal conduction.