Autophagy plays an important role in neoplastic transformation of cells and in resistance of cancer cells to radio- and chemotherapy. p62 (SQSTM1) is a key component of autophagic machinery which is also involved in signal transduction. Although recent empirical observations demonstrated that p62 is overexpressed in variety of human tumors, a mechanism of p62 overexpression is not known. Here we report that the transformation of normal human mammary epithelial cells with diverse oncogenes (RAS, PIK3CA and Her2) causes marked accumulation of p62. Based on this result, we hypothesized that p62 may be a feasible candidate to be an anti-cancer DNA vaccine. Here we performed a preclinical study of a novel DNA vaccine encoding p62. Intramuscularly administered p62-encoding plasmid induced anti-p62 antibodies and exhibited strong antitumor activity in four models of allogeneic mouse tumors – B16 melanoma, Lewis lung carcinoma (LLC), S37 sarcoma, and Ca755 breast carcinoma. In mice challenged with Ca755 cells, p62 treatment had dual effect: inhibited tumor growth in some mice and prolonged life in those mice which developed tumor size similar to control. P62-encoding plasmid has demonstrated its potency both as a preventive and therapeutic vaccine. Importantly, p62 vaccination drastically suppressed metastasis formation: in B16 melanoma where tumor cells where injected intravenously, and in LLC and S37 sarcoma with spontaneous metastasis. Overall, we conclude that a p62-encoding vector(s) constitute(s) a novel, effective broad-spectrum antitumor and anti-metastatic vaccine feasible for further development and clinical trials.
Objectives: NSC631570 is a cytotoxic drug with the ability to be selectively accumulated in tumor tissue and activate apoptosis only in malignant cells and not in normal cells. Therapy with NSC631570 is accompanied by the stimulation of anticancer immune responses. It is known that cytotoxic anticancer drugs have additional effects on the immune system of tumor-bearing organism by increasing the immunogenic properties of tumor cells. This study aimed to investigate the immunogenicity of melanoma B16 after treatment with NSC631570. Methods: Two melanoma B16 sublines with different metastatic potentials were used. For in vivo growth cells were inoculated intravenously into C57BL/6 mice. The anticancer effect was calculated according to the growth inhibition index. Cell viability was determined by the MTT test. Cell apoptosis and necrosis were assessed by flow cytometry. HMGB1 expression, the serum level of cytokines and cytokine profile in tumor tissue were determined by ELISA. TAP1 and TAP2 expression was evaluated in RT-PCR and by Western blot. Results: Treatment of melanoma B16 cells with NSC631570 at apoptogenic concentrations induced tumor cell death accompanied by dose-dependent HMGB1 release in vitro. At the nonapoptogenic concentration the preparation caused an increase in TAP expression. The therapeutic efficacy of NSC631570 was also associated with strong release of HMGB1 in the serum of tumor-bearing mice and was more expressed in the case of the high-metastatic tumor variant. The therapeutic effect was accompanied by an increase of levels of Th1 cytokines in the serum and in tumor tissue of treated animals. Conclusion: In addition to the direct induction of tumor cell apoptosis, the preparation can increase the tumor immunogenicity.
Aim: To study the effect of long-term impact of mouse interferon-beta (IFN-b) on the behavior of mouse melanoma cells in vitro and in vivo and the expression of epithelial-mesenchymal transition (EMT) associated proteins. Materials and Methods: Studies were performed on mouse B16 melanoma cells as a tumor model (MM-4 cell line). Immunocytochemical and tumor cell biology approaches have been used in this study. Results: Long-time treatmentof MM-4 melanoma cellswith low-dose IFN-b (1/2 of IC50) leads to change their morphology, significant inhibition of cell growth and plating efficiency, suppression of cell migration and anchorage-independent growth in semisolid agar. Moreover, IFN-modification of melanoma cells is accompanied by the significant suppression of their malignancy in vivo: growth of tumor induced by IFN-treated cells has inhibited on 50% and growth of metastases - on 90%. Also, IFN-modification of MM-4 cells affects on the expression of proteins involved in cell cycle regulation and inhibits expression of some molecules of adhesion (N-, VE-cadherins), but not influence on the expression of EMT-associated Twist and Slug proteins and E-cadherin. Conclusions: Long-term impact of mouse IFN-beta in low dose on melanoma cells in vitro changes their phenotype and inhibits their proliferative potential, signs of malignancy in vitro, tumorigenicity and metastatic ability in vivo. Loss of malignancy is associated with inhibition of N- and VE-cadherins expression, but not associated with the change of expression and subcellular localization of E-cadherin and EMT transcription factors Twist and Slug.
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