Proteasome functioning in breast cancer: connection with clinical-pathological factors.

Breast cancer is one of four oncology diseases that are most widespread in the world. Moreover, breast cancer is one of leading causes of cancer-related deaths in female population within economically developed regions of the world. So far, detection of new mechanisms of breast cancer development is very important for discovery of novel areas in which therapy approaches may be elaborated. The objective of the present study is to investigate involvement of proteasomes, which cleave up to 90% of cellular proteins and regulate numerous cellular processes, in mechanisms of breast cancer development. Proteasome characteristics in 106 patient breast carcinomas and adjacent tissues, as well as relationships of detected proteasome parameters with clinical-pathological factors, were investigated. Proteasome chymotrypsin-like activity was evaluated by hydrolysis of fluorogenic peptide Suc-LLVY-AMC. The expression of proteasome subunits was studied by Western-blotting and immunohistochemistry. The wide range of chymotrypsin-like activity in tumors was detected. Activity in tumors was higher if compared to adjacent tissues in 76 from 106 patients. Multiple analysis of generalized linear models discovered that in estrogen α-receptor absence, tumor growth was connected with the enhanced expression of proteasome immune subunit LMP2 and proteasome activator PA700 in tumor (at 95% confidence interval). Besides, by this analysis we detected some phenomena in adjacent tissue, which are important for tumor growth and progression of lymph node metastasis in estrogen α-receptor absence. These phenomena are related to the enhanced expression of activator PA700 and immune subunit LMP7. Thus, breast cancer development is connected with functioning of immune proteasome forms and activator PA700 in patients without estrogen α-receptors in tumor cells. These results could indicate a field for search of new therapy approaches for this category of patients, which has the worst prognosis of health recovery

Expression of proteasome immune subunits and Rpt6 subunit in breast samples at different disease stages.

<p>Western-blotting was performed with the use of mouse mAbs to proteasome subunits LMP2, LMP7 and Rpt6; β-actin was detected as the inner control with the use of mouse mAbs to this protein. TT, tumor tissue. AT, adjacent tissue.</p

Regulatory network between ERα and proteasome immune subunit LMP2 in breast cancer.

<p>MIR, microRNA; SOX4, PU.1 (SPI 1), MYC, transcription factors. Created within open informatics site MirOB, (<a href="http://mirob.interactome.ru/pathway_navigator" target="_blank">http://mirob.interactome.ru/pathway_navigator</a>, 2012−2013).</p

Statistical indicators for revealed dependence of the proteasome parameters in breast samples on simultaneous effect of clinical-pathological factors.^1.

1<p>Multiple GLM (generalized linear models) analysis was applied;</p>2<p>F (DF), F-test value for indicated pair of interacting signs (Degrees of Freedom);</p>3<p><i>p</i>, statistical significance of observed effects.</p><p>Statistical indicators for revealed dependence of the proteasome parameters in breast samples on simultaneous effect of clinical-pathological factors.^1.</p

Confocal images of cells in slices of IDC after double immunofluorescent labeling.

<p>(Panel A) Rabbit pAbs to LMP7 subunit and mouse mAbs to α1,2,3,5,6,7 subunits. (Panel B) Rabbit pAbs to LMP7 subunit and mouse mAbs to Rpt6 subunit. IDC, invasive ductal carcinoma. Scale bar, 100 µm.</p

Dependence of amount of proteasome subunits in breast samples on simultaneous effect of two factors.

<p>TT, tumor tissue. AT, adjacent tissue. Factors: lymph node metastasis and histological tumor type. Wilks lambda = 0.014; F(40; 77.7) = 4.02; <i>p</i><0.001. IDC, invasive ductal carcinoma. ILC, invasive lobular carcinoma. MdC, medullary cancer. McC mucinous cancer. Vertical bars denote 95% confidence interval.</p

Dependence of ChTL activity difference in tumor and adjacent tissue on ChTL activity in breast samples.

<p>(A) F(1) = 519.763; <i>p</i><0.001. (B) F(1) = 0.947; <i>p</i> = 0.333. Calculated at 95% confidence.</p

Expression of immune subunits LMP2 and LMP7 in cytokeratin 18 containing cells of IDC sample.

<p>(Panels A) Mouse mAbs to cytokeratin 18, rabbit pAbs to LMP2. (Panels B) Mouse mAbs to cytokeratin 18, rabbit pAbs to LMP7. IDC, invasive ductal carcinoma. Scale bar, 100 µm.</p