Changes in proteasome pool in human papillary thyroid carcinoma development

Proteasomes in Patient Rectal Cancer and Different Intestine Locations: Where Does Proteasome Pool Change?

A special problem in the surgery of rectal cancer is connected with a need for appropriate removal of intestine parts, along with the tumor, including the fragment close to the sphincter. To determine the length of fragments to remove, it is necessary to reveal areas without changes in molecule functioning, specific for tumor. The purpose of the present study was to investigate functioning the proteasomes, the main actors in protein hydrolysis, in patient rectal adenocarcinoma and different intestine locations. Chymotrypsin-like and caspase-like activities, open to complex influence of different factors, were analyzed in 43-54 samples by Suc-LLVY-AMC- and Z-LLE-AMC-hydrolysis correspondingly. Both activities may be arranged by the decrease in the location row: cancer→adjacent tissue→proximal (8-20 cm from tumor) and distal (2 and 4 cm from tumor) sides. These activities did not differ noticeably in proximal and distal locations. Similar patterns were detected for the activities and expression of immune subunits LMP2 and LMP7 and expression of 19S and PA28αβ activators. The largest changes in tumor were related to proteasome subtype containing LMP2 and PA28αβ that was demonstrated by native electrophoresis. Thus, the results indicate a significance of subtype LMP2-PA28αβ for tumor and absence of changes in proteasome pool in distal fragments of 2-4 cm from tumor.

Combined Effect of Bortezomib and Menadione Sodium Bisulfite on Proteasomes of Tumor Cells: The Dramatic Decrease of Bortezomib Toxicity in a Preclinical Trial

Tumor growth is associated with elevated proteasome expression and activity. This makes proteasomes a promising target for antitumor drugs. Current antitumor drugs such as bortezomib that inhibit proteasome activity have significant side effects. The purpose of the present study was to develop effective low-toxic antitumor compositions with combined effects on proteasomes. For compositions, we used bortezomib in amounts four and ten times lower than its clinical dose, and chose menadione sodium bisulfite (MSB) as the second component. MSB is known to promote oxidation of NADH, generate superoxide radicals, and as a result damage proteasome function in cells that ensure the relevance of MSB use for the composition development. The proteasome pool was investigated by the original native gel electrophoresis method, proteasome chymotrypsin-like activity-by Suc-LLVY-AMC-hydrolysis. For the compositions, we detected 10 and 20 μM MSB doses showing stronger proteasome-suppressing and cytotoxic in cellulo effects on malignant cells than on normal ones. MSB indirectly suppressed 26S-proteasome activity in cellulo, but not in vitro. At the same time, MSB together with bortezomib displayed synergetic action on the activity of all proteasome forms in vitro as well as synergetic antitumor effects in cellulo. These findings determine the properties of the developed compositions in vivo: antitumor efficiency, higher (against hepatocellular carcinoma and mammary adenocarcinoma) or comparable to bortezomib (against Lewis lung carcinoma), and drastically reduced toxicity (LD50) relative to bortezomib. Thus, the developed compositions represent a novel generation of bortezomib-based anticancer drugs combining high efficiency, low general toxicity, and a potentially expanded range of target tumors.

Changes in proteasome chymotrypsin-like activity during the development of human mammary and thyroid carcinomas

Changes in the proteasome chymotrypsin-like activity in mammary and thyroid carcinomas in comparison with the adjacent tissue were studied at stages T(1-4)N(0-3)M(0) and T(2-3)N(0-1)M(0), respectively. The activities changed in a wave-like manner over the course of mammary carcinoma growth in cases with and without metastases. The minimum increment of the activity in the tumor was recorded during the T(2)N(0) stage in the absence of local metastases. The increment of the activity reached the peak in N(1) tumors of the same size with metastases. The activities in the tumor and adjacent tissues virtually did not differ during the T(3-4)N(1-3) stages. The time course of proteasome activity changes in thyroid tumors of the studied stages was similar to that in mammary carcinoma. The results can be used for development of methods for evaluating the aggressiveness of mammary and thyroid tumors.