New progress in the basic research of stem cells / 基础医学与临床

During the recent 5 years,an upsurge of stem cell biology research has appeared around the world with a huge number of papers published.A part of them,however,concluded with a hypothesis of so called "transdifferentiation" or "stem cell plasticity" that stem cells could transform into any other tissues such as fats becoming liver or muscle changing into nervous cells and so on,that all lacks of strong evidence.The discovery of adult stem cells(ASC) in the adult tissues was actually a great scientific epoch-making towards the end of 1999 though the authors made a wrong conclusion of transdifferentiation at that time.More and more evidences showed that the ASC in the adult tissue are the remnants of stem cells from every stage of embryonic development.The tissue specific stem cells harbored in the adult tissues can only be induced to differentiate in the progeny cells of its own committed origin.ASC includes hematopoietic and non-hematopoietic stem cells and there are lots of stem cells in the latter,like nervous stem cells and mesenchymal stem cells(MSC).The progenies of MSC are the connective tissues,such as osteoblasts,chodroblasts,myocytes,angio-endothelio cells,etc,which are most important during the recovery and reconstitution of tissue injury,ischemic necrosis and hematopoietic damage.

The Therapeutic Effects of Intratumoral Injection with MHC Class Ⅱ Gene on Tumor-Bearing Mice / 中国肿瘤生物治疗杂志

Many gene therapy protocols can induce antitumor immunity, however, the ex vivo approach restricts their uses. This sutydy intended to induce antitumor immunity by direct transfer of MHC class Ⅱ gene in vivo. Methods: MHC class Ⅱ gene cDNA was introduced directly into two tumors: P815, (a murine weak immunogenic mas-tocytoma) and B16 (a murine nonirnmunogenic melanoma) to observe the survival rate of the mice. Results: Tumori-genicity of P815 was reduced when MHC class Ⅱ gene was introduced directly into tumors in vivo. Further more, most vaccinated mice could survive after second challenge of P815. Co-injection of MHC class Ⅱ and B7 genes in the B16 also resulted in the tumor grow slowly, while the injection of MHC class Ⅱ gene was not enough to induce effective antitumor responses. Conclusion: The results showed the potential applications of direct transfer of MHC class Ⅱ gene in the treatment of tumor.

Effect of Retroviral Vector-Mediated IL6/IL2 Fused Gene Transduction on B16 Melanoma Cells Adhesive and Metastatic Potential / 中国肿瘤生物治疗杂志

In order to examine the feasibility of cytokine fusion gene transfer into tumor cells, a retroviral vector (pLXSN) for human interleukin 6/interleukin 2 (IL6/IL2) fusion gene was constructed by using PCR and ligating the 2 genes with a synthesized flexible linker. The IL6/IL2 fused gene was introduced into B16 melanoma cell line mediated by retrovirus and the changes of adhesive and metastatic ability of fused gene-modified cells were detected. The B16-IL6/ IL2 cells showed efficient expression of both cytokines and decreased binding affinity with extracellular matrix (Laminin and Matrigel), accompanying with decreased experimental metastatic potentials. These data suggest that the mechanism involving the decreased metastases may relate with the changes of biological characteristics and immune stimulating activity of gene-modified cells.