This review describes the most popular methods of search for serological markers of tumors that are used in clinical setting, provided with comparison of their efficiency.

This review describes the most popular methods of search for serological markers of tumors that are used in clinical setting, provided with comparison of their efficiency.

It was demonstrated that enteric alpha-defensin 5 is undetectable in five blood serum samples of healthy donors, whereas its processed form is present in two out of five serum samples of colon cancer patients. Obtained results open a possibility of serological diagnosis of colon tumors in high risk cancer patients.

Разработан новый алгоритм биоинформатического поиска потенциальных сывороточных маркеров опухолей, включающий: 1) идентификацию микроРНК, уровень синтеза которых наиболее заметно и часто понижается в опухолях; 2) поиск мРНК-мишеней, регулируемых микроРНК; 3) отбор мишеней, кодирующих секреторные белки; 4) сравнительный анализ уровней транскрипции мишеней в нормальных и опухолевых тканях. Практическое использование алгоритма позволило обнаружить семь потенциальных сывороточных маркеров опухолей толстой кишки: ADAMTS14, ANGPT2, CCL7, DEFA5, MMP11, MMP14 и PLAU. Экспериментально показано, что уровень синтеза двух из семи белков (MMP14 и DEFA5) в опухолях толстой кишки значительно превышает уровень в нормальной ткани.

A new algorithm has been developed for bioinformatics search of putative serum markers of cancer, which includes: 1) identification of microRNAs that are most often and most significantly overexpressed in tumors; 2) selection of mRNA targets regulated by microRNAs; 3) identification of mRNA targets encoding secreted proteins; 4) comparative analysis of mRNA transcription levels in normal and tumor tissues. Application of the algorithm led to discovery of seven putative serum markers of colon cancer: ADAMTS14, ANGPT2, CCL7, DEFA5, MMP11, MMP14, and PLAU. Experiments demonstrated that production of two out of seven proteins (MMP14 and DEFA5) is significantly increased in colon tumors vs. normal samples.

В результате сравнительного анализа уровня синтеза белков в интестинальных и диффузных опухолях желудка и в нормальных тканях, выполненного методом двумерного гель-электрофореза, идентифицированы три белка (SOD2, S100A6 и TXN), содержание которых в опухолях значительно выше, чем в нормальных тканях. При этом повышение уровня синтеза белков SOD2 и TXN гораздо чаще наблюдается в диффузных опухолях, чем в интестинальных. На основе опубликованных данных отобрана контрольная панель из 11 белков, содержание которых, согласно данным двумерного электрофореза, в опухолях желудка заметно выше, чем в нормальных тканях. Биоинформатический поиск мРНК, кодирующих белки из контрольной панели, в базе данных Oncomine, содержащей результаты определения уровней транскрипции мРНК в нормальных и опухолевых тканях, выявил совпадение данных протеомного и транскриптомного анализа для семи из 11 белков.

The review presents the data on clinical characteristics of two different histological types of gastric cancer and molecular factors of pathogenesis including Helicobacter pylori infection, inherited and somatic mutations and other genetic disturbances. The analysis of relation of the markers of proliferation, apoptosis, growth factors and regulators of intercellular interactions to the tumor progression was carried out. The results of proteomic studies on the search for diagnostic markers and prognosis of intestinal and diffuse types of gastric cancer were presented.

Modification of 2D analysis protocol was developed, based on preliminary removal of major cellular proteins by extraction with buffer saline and elimination of high molecular weight proteins by gel filtration. This approach allowed identification of 12 proteins with increased expression levels in tumors versus normal tissues. Increase in expression levels of the eight proteins in colon tumors was discovered for the first time. We performed comparison of marker search efficiency by 2D analysis and SAGE in a control panel of 19 putative colon cancer markers, discovered by us previously and at the same time independently identified by other authors. Results of 2D analysis of control panel completely coincided with published data, as compared to search in SAGE database, which allowed identification of only one third of markers.

Highly sensitive techniques of comparative 2D-proteomic analysis were used as a prospective tool in the search for protein markers with consistently differing levels in normal and tumor tissues in stomach cancer patients. We performed the proteomic analysis of protein extracts which are primarily depleted of major physiologically insoluble structural proteins. After the evaluation of four paired gels, we selected six proteins the level of which in two or more tumor specimens was at least 10-fold higher than in the paired normal tissue (thymosin beta-10, cathepsin D (CTSD), S100 calcium binding protein A9 (S100A9), tropomyosin 3 and cyclophillin A. These proteins were identified by mass-spectrometry. For five of the six proteins, the observed upregulation in gastric adenocarcinoma is in agreement with the data of other recent studies. At the same time, our study is the first one to report consistently increased hCG1816442 levels in gastric tumors. Cyclophilin A is the most promising to further investigation to assay its prognostic value, since its expression level is low in most normal tissues and tumors of other localizations