Abstract. In the present study, we analyzed differential composition of blood serum from Ehrlich carcinoma-bearing and healthy male C57Bl/6 mice by isolating complexes of hemoglobin and other serum proteins by a proteomic approach (gel filtration, gel electrophoresis, and mass spectrometry). The hemoglobin fractions isolated from the serum of micebearing tumors contained several proteins with molecular weights of 15, 65, 68, and 100 kDa, while hemoglobin fractions isolated from the serum of healthy mice did not contain additional protein bands. These bands were identified by MALDI-TOF as haptoglobin, serum albumin, a homologue of α-fetoprotein, and hemoglobin-α. Ion exchange chromatography indicated complex formation of these proteins. Injection of hemoglobin-associated blood serum proteins (HAP) isolated from tumor-bearing animals, leads to tumor regression. Intraperitoneally injected HAP-induced apoptosis in Ehrlich carcinoma cells but not normal peritoneal cells and led to a complete regression of the ascitic or solid Ehrlich carcinoma. A one-year follow up of the animals did not reveal any signs of tumor growth. In conclusion, HAP might be a novel principle of tumor regression. The clinical relevance of these findings with Ehrlich carcinoma should be investigated in the future.

PurposeMost colon cancers show low sensitivity to treatment with oxaliplatin and a specific strategy is needed to overcome this problem. Our approach uses RNA interference to silence the expression of target genes responsible for the development of oxaliplatin resistance. Profile analysis of genes related to the regulation of apoptosis allowed identification of target genes showing the greatest degree of upregulation in response to oxaliplatin exposure.MethodsWe designed a panel of genes with functions closely related to inactivation of the caspase cascade, endoplasmic reticulum stress reduction, and drug metabolism. The candidate genes were silenced by means of specific small interfering RNA (siRNA) oligonucleotides.ResultsThe caspase 3 and 9 inhibitors of apoptosis 2 (cIAP2) and LIVIN were found to be the most dose-responsive genes during the period of oxaliplatin treatment. Two-fold sensitization of cells to oxaliplatin was observed with independent knockdown of either cIAP2 or LIVIN expression. siRNA-silencing of both targets produced a five-fold increase in oxaliplatin sensitivity of HCT-116 cells.ConclusionA dose-dependent approach revealed reliable targets for siRNA-silencing under low doses of oxaliplatin. Targeting the key proapoptotic chain with several specific siRNAs resulted in synergetic sensitization of HCT-116 cells to oxaliplatin treatment.