Immuno-hormonal regulation of tumor proliferation in breast cancer patients

Abstract

It is well known that tumor cells proliferation is regulated by sex steroid hormones, estradiol and progesterone (E2 and Pg) in breast cancer patients (BCP). Moreover, specific auto-antibodies to estrogen receptor (ERα) were detected in blood serum of BCP. Their levels positively correlated with the percentage of Ki-67 expressing breast cancer cells. We proposed that antiidiotypic auto-antibodies to E2 and Pg (IgG2-E2 and IgG2-Pg) could act as antibodies against membrane ER and progesterone receptor (PR). Our study aimed for research of IgG2-E2 and IgG2-Pg according to E2 and Pg serum levels in association with Ki-67 positive tumors in BCP. Antiidiotypic antibodies were studied in ER-positive patients with breast cancer (stage I, n = 374, and stage II-IV, n = 379,) using ELISA technique with monoclonal antibodies against E2 and Pg as adsorbed antigens. Blood serum concentrations of E2 and Pg were measured using “ImmunoEA-Estradiol” and “ImmunoEA-Progesterone” test-systems (“Immunotech”, Russia). Tumor Ki-67 was studied by standard immunohistochemical technique at the Kemerovo Oncological Hospital. Higher percentage of Ki-67 positive breast cancer cells (Ki-67 30) was increased in BCP II-IV stages compared with stage I patients (50.7% vs 29.8%, p 0,001). Such increased values were detected for the BCP with low levels of both IgG2-E2 and IgG2-Pg antibodies in the following subgroups: 1) at low serum E2 concentration of ≤ 200 pmol/L (50.9% vs 21.3%, р 0.001); 2) at the E2 exceeding 200 pmol/L (74.2% vs 34.1%, р = 0.003); 3) at the Pg levels under 600 pmol/L (60.6% vs 22.2%, р 0.001); 4) at Pg values exceeding 600 pmol/L (58.5% vs 30.8%, р = 0.02). Similar differences were not revealed between stage II-IV and stage I BCP with low levels of both IgG2-E2 and IgG2-Pg. Corresponding Ki-67 30 indices were as follows: 1) 36.9% vs 22.0% (р = 0.14); 2) 48.4% vs 34.5% (р = 0.08); 3) 34.0% vs 27.7% (р = 0.75). Significant differences were detected in BCP with Pg 600 pmol/L and high IgG2-E2 and IgG2-Pg levels only: 48.1% vs 26.6%, (р = 0.01). Hence, antiidiotypic auto-antibodies to steroid hormones may participate in regulation of tumor proliferation in BCP. Immunoassay of IgG2-E2 and IgG2-Pg may be used for prognosis of tumor proliferation upon breast cancer progression.