Studies of tumor and MSCs interactions.

• Other Authors: Zhang, Ting
• Format: Others
• Language: English; Chinese
• Published: 2013
• Subjects: Stem cells > Therapeutic use; Cancer > Treatment; Gene therapy; Stem Cell Transplantation; Neoplasms > therapy; Genetic Therapy
• Online Access: http://library.cuhk.edu.hk/record=b5549810; http://repository.lib.cuhk.edu.hk/en/item/cuhk-328551

惡性腫瘤嚴重威脅著人類的身體健康，其治療也成為人類關注的焦點。傳統的化學療法和放射療法由於缺乏特異性，取得療效的同時往往也帶來較大的毒副作用。隨著對腫瘤發生發展分子機制認識的不斷深入，腫瘤的基因治療已成為攻克和治愈腫瘤最具希望和挑戰的研究領域。近年來研究發現骨髓間充斥幹細胞(MSCs)可被募集至腫瘤或損傷部位并參與腫瘤生長或組織修復，研究證明間充斥幹細胞通過靜脈注入帶瘤鼠（比如乳腺癌、膠質瘤、結腸癌及黑色素瘤）體內后，特異性的分佈于生長中的腫瘤中。這種特異性向腫瘤組織趨化轉移的特性使得骨髓間充斥幹細胞成為腫瘤基因靶向治療的載體的理想細胞。酶蛋白基因如單純皰疹病毒胸苷激酶(HSV-TK)可以使一些無毒或低毒的前藥轉化為強細胞毒性物質，殺死腫瘤細胞。我們前期實驗結果表明，通過遺傳改造后的表達TK基因的MSCs在GCV的存在下，具有殺傷腫瘤細胞抑制腫瘤生長的能力。但沒有改造的MSCs遷移至腫瘤之後可能會分化成成纖維細胞或者腫瘤基質細胞等支持腫瘤生長，但其命運和影響到底如何，我們怎麼樣進一步促進其向腫瘤的遷移以提高殺傷腫瘤的效率是本研究需要解決的問題。 === 本研究擬採用免疫螢光組織化學技術和分子生物學等技術研究和觀察MSCs對腫瘤（以乳腺癌，前列腺癌為例）的趨化過程及其在腫瘤生長中的作用，在在此基礎上研究促進攜帶HSV-TK自殺基因的MSCs的腫瘤靶向性細胞治療策略，採用分子和細胞生物學等方法評估其對荷瘤鼠體內腫瘤殺傷的原理，為利用TK-MSCs腫瘤的靶向治療奠定基礎。 === 研究結果顯示體外共培養的條件下，小鼠骨髓間充斥幹細胞可促進小鼠乳腺癌細胞增長，且增長速度同培養體系中間充斥幹細胞數目呈正相關。將兩種細胞混合注射于裸鼠體內，相比共注射小鼠皮膚成纖維細胞，間充斥幹細胞可促進體內腫瘤生長。使用人胚胎骨髓間充斥幹細胞和前列腺癌細胞可得出類似的效果。將腫瘤組織切片分析發現間充斥幹細胞促進體內腫瘤細胞增殖的同時，提高了腫瘤組織內血管密度。體外實驗發現共培養前列腺癌細胞和間充斥幹細胞可促進血管生成且在間充斥細胞內同血管增生相關的蛋白表達量都有相應提高，進一步證實間充斥幹細胞可能通過促進血管增生從而促進腫瘤生長。另外，我們利用人胚胎來源的骨髓間充斥幹細胞建立了穩定表達TK自殺基因的細胞系，且在GCV的存在下具有抑制腫瘤生長的能力。為了促進它們向腫瘤遷移的能力，我們用多柔比星預處理腫瘤細胞，和沒處理過的對照組相比，能增強對表達TK的間充斥幹細胞的招募能力。且在聯合利用多柔比星和TK的條件下，腫瘤生長能得到較大程度的抑制，這種抑制作用强於單獨使用多柔比星和表達自殺基因的間充斥幹細胞系統。初步認為是多柔比星的處理能增強腫瘤組織內炎性介質的分泌從而增強間充斥幹細胞的遷移達到增強自殺基因系統殺死腫瘤細胞的目的。 === 總的來說，雖然間充質幹細胞對腫瘤的生長存在一定的促進作用，但我們仍能對其進行遺傳改造，且在其它抗腫瘤藥的配合下達到最大的抗腫瘤效果。 === Eradication of cancer, especially when it has metastasized is extremely difficult and conventional cancer therapies are simply unable to specifically target tumors/cancers, thus causing unwanted side effects and complications. Recently, it has been shown that bone marrow mesenchymal stem cells (MSCs) are able to migrate specifically to tumors and contribute to the formation of tumor-associated stroma. These properties make MSCs good candidates as anti-tumor agent delivery vehicles and lead to a great deal of interest in the possibility of genetically modifying MSCs to express anticancer molecules and using them as specific targeted anticancer agents. We and others have showed that MSCs have the ability to migrate towards various cancer cells including breast, colon, fibrosarcoma and prostate cancer cells. Suicide gene therapy is widely used in cancer gene therapy. When stably infected with herpes simplex virus thymidine kinase gene by lentivirus, TK-MSCs maintained their MSCs characters and tumor tropism potential and significantly inhibited tumor growth, in the presence of the pro-drug ganciclovir (GCV). Improve MSCs homing to tumor tissue as anti-tumor gene therapy vehicles and maximizing their tumor killing effects is highly warranted. Furthermore, MSCs interact with tumor cells in numerous ways, which have the potential to support or suppress tumor growth. Therefore the fate and role of MSCs engrafted in tumor sites need to be clarified in order to making better use of these cells as anti-cancer agent delivery vehicles. === The aims of the current study are: (1) to study the role and fate of MSCs homed into the tumors; (2) to establish human bone marrow MSCs that stably express the TK genes; (3) to investigate the methods that enhance the anti-tumor efficiency of TK-MSCs. === In this study, bone marrow-derived mesenchymal stem cells from mice or human fetus were isolated and characterized. Effects of BM-MSCs on tumor cell proliferation in vitro were analyzed in a co-culture system with mouse breast cancer cell 4T1 cells. Both co-culture with BM-MSCs and treatment with MSC-conditioned medium led to enhanced growth of 4T1 cells. Co-injection of 4T1 cells and MSCs into nude mice led to increased tumor size compared with injection of 4T1 cells alone. Identical experiments using human prostate cancer cell DU145 cells and hBM-MSCs instead of 4T1 cells and mBM-MSCs yielded similar results. Compared with tumors induced by injection of cancer cells alone, tumor vessel area was greater in tumors from co-injection of 4T1 or DU145 with BM-MSCs, which correlated with decreased central tumor necrosis and increased tumor cell proliferation. Furthermore, both conditioned medium from co-cultures of hBM-MSCs and DU145 cells or hBM-MSCs alone was able to induce angiogenesis in human umbilical vein endothelial cells (HUVEC). When hBM-MSCs exposed to DU145 cells environment, the expression of markers associated with neovascularization (α-SMA, VEGF, TGF-β and IL6) were increased. Together, these results indicate that MSCs promote tumor growth both in vitro and in vivo and suggest that tumor promotion in vivo may be attributable in part to enhanced angiogenesis. === Immortalized human fetal bone marrow-derived MSCs (hfBMSCs) expressing herpes simplex virus thymidie kinase was established by conventional lentiviral transduction method. Functional expression of TK was evaluated by cytotoxicity in the presence of its prodrug GCV. SV40-TK-hfBMSCs exhibited comparable proliferation, surface phenotype expression, multi-differentiation potential and tumor-tropic migration ability as hfBMSCs. By measurement of tumor volume, repeated injection of the SV40-TK-hfBMSCs and subsequent consecutive GCV administration could suppress tumor growth in DU145 or PC3 human prostate tumor xenograft nude mice model without causing weight loss. However, its clinical applications are still limited. Alternative strategies have been pursued in this study by the use of combination therapy with cytotoxic chemotherapy to improve the overall efficacy of the TK-hfBMSCs/GCV system. === TK-hfBMSCs/GCV was evaluated alone or combined with low-dose doxorubicin in human prostate carcinoma DU145 xenografts in nude mice, testing for effects on local growth and overall survival. Tissues were evaluated through immunofluorescence and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling staining (TUNEL) for treatment effects on tumor cell proliferation and apoptosis. Transwell migration assay was used to access the migration ability of TK-hfBMSCs to tumor cells upon doxorubicin treatment and caspase-3 activity was conducted for test the tumor cells apoptosis under TK-hfBMSCs/GCV, doxorubicine, or combination of the two compound treatments respectively. Only minimal growth inhibition was observed in DU145 after treatment with TK-hfBMSCs/GCV or doxorubicin alone at doses and time points as indicated. In contrast, the combination of both agents resulted in a significant growth inhibition. Caspase-3, plays a central role in the execution-phase of cell apoptosis, was increased by TK-hfBMSCs/GCV or doxorubicine and also to a much greater extent by the combination treatment. Treatment by TK-hfBMSCs/GCV resulted in only a slight decrease in tumor growth compared with controls. Treatment with low-dose doxorubicin alone resulted in a small, nonstatistically significant decrease in tumor growth; In contrast, combined low-dose doxorubicin and TK-hfBMSCs/GCV was markedly inhibitory compared with control, doxorubicin alone, or TK-hfBMSCs/GCV alone. During the whole treatment process, no significant weight loss was observed. Furthermore, combined therapy induced increased area of necrosis, significant apoptosis and decreased tumor cell proliferation in treated tumors. Taken together, low dosage of doxorubicin could be used in combination with TK-hfBMSCs based suicide gene therapy. === In conclusion, we have demonstrated that BM-MSCs could increase the growth of human prostate cancer and mouse breast cancer. The promotion effect may partly attribute to the increased expression of pro-angiogenic factors in BM-MSCs in tumor microenvironment and subsequent enhancement in angiogenesis and tumor growth. The current study also suggests combination of TK-hfBMSCs/GCV and doxorubicin was more effective in inhibiting prostate cancer cells growth than TK-hfBMSCs/GCV or doxorubicin alone. Although many problems need to be resolved for further application, our study provided the possibility of a new strategy of suicide gene-based therapy accompanied by low dosage of chemotherapy in treating prostate cancer. Therefore MSCs were described as a “double-edged sword in their interaction with tumors. However, if MSCs are suitably engineered with anticancer genes they could be employed as a valuable “single-edged sword“ against cancers. === Detailed summary in vernacular field only. === Detailed summary in vernacular field only. === Detailed summary in vernacular field only. === Detailed summary in vernacular field only. === Zhang, Ting. === Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. === Includes bibliographical references (leaves 120-158). === Abstracts also in Chinese. === ACKNOWLEDGEMENT --- p.ii === PUBLICATIONS --- p.vii === ABSTRACT --- p.xiii === Chapter CHAPTER 1 --- Introduction --- p.1 === Chapter 1.1 --- Mesenchymal stem cells (MSCs) --- p.2 === Chapter 1.2 --- Tumor microenvironment and involvement of MSCs in tumor establishment --- p.5 === Chapter 1.3 --- Tumors-tropic characteristics of MSCs --- p.15 === Chapter 1.4 --- Impact of MSCs on in vivo tumors --- p.21 === Chapter 1.5 --- In vivo imaging demonstrating MSCs tumor-homing potentials --- p.25 === Chapter 1.6 --- Evidence for use of MSCs as anti-tumor agents delivery vehicles --- p.26 === Chapter 1.7 --- Homing strategies to enhance efficacy and safety of MSCs therapy --- p.32 === Chapter 1.8 --- Summary --- p.35 === Chapter CHAPTER 2 --- Hypotheses, Objectives and Study Design --- p.35 === Chapter 2.1 --- Hypothesis --- p.35 === Chapter 2.2 --- Objective --- p.36 === Chapter 2.3 --- Study design --- p.37 === Chapter CHAPTER 3 --- Bone Marrow-derived Mesenchymal Stem Cells Promote Growth and Angiogenesis of Breast and Prostate Tumors (Study I) --- p.40 === Chapter 3.1 --- Materials and Methods --- p.40 === Chapter 3.2 --- Results --- p.49 === Chapter 3.3 --- Discussion --- p.64 === Chapter 3.4 --- Conclusions --- p.67 === Chapter CHAPTER 4 --- Immortalized human fetal bone marrow-derived mesenchymal stem cell expressing anti-tumor suicide gene for anti-tumor therapy in vitro and in vivo (Study II) --- p.68 === Chapter 4.1 --- Materials and Methods --- p.68 === Chapter 4.2 --- Results --- p.73 === Chapter 4.3 --- Discussion --- p.85 === Chapter CHAPTER 5 --- Enhanced antitumor effects by combination therapy using mesenchymal stem cell expressing anti-tumor suicide gene and Doxorubicin in a xenograft mouse model (Study III) --- p.89 === Chapter 5.1 --- Materials and Methods --- p.89 === Chapter 5.2 --- Results --- p.97 === Chapter 5.3 --- Discussion --- p.111 === Chapter CHAPTER 6 --- General discussion and conclusions --- p.116 === Chapter 6.1 --- General discussion --- p.116 === Chapter 6.2 --- General conclusions --- p.119 === FUNDING --- p.120 === REFERENCE --- p.120