本研究計畫的總目標是要了解骨髓微環境中的人類間質幹細胞（hMSCs）在癌症骨轉移 過程中與癌細胞間之交互作用，並根據其與骨轉移性癌細胞間特有的趨化性設計標靶溶 瘤病毒治療的策略。在之前的研究資助期間，我們已經證明: 1. hMSCs與前列腺癌細胞 的共同演化增加了他們分化的能力以及促進癌症的發展。 2. hMSCs藉由IL-6對IL - 6受體 激活產生對骨轉移的前列腺癌細胞的趨化性。3. hMSCs受到維生素D3的誘導能有效複製 骨鈣素啟動子控制的Ad-hOC-E1溶瘤腺病毒載體。 最後，在人類腎細胞癌（RCC）異種 移植瘤的動物體內給予全身性攜帶Ad-hOC-E1之hMSC維持其移行到RCC的能力並有效 的抑制腫瘤的生長。 這些結果顯示使用治療性之hMSCs有可能在體內成為反應基質而 促進腫瘤生長。因此，這一延續性研究計畫的目的是為了進一步了解骨轉移的癌細胞透 過何種分子來誘導hMSCs變成反應基質（目標 1）; 藉由鑑定關鍵性蛋白激?激活的模 式來解析IL-6/IL-6R對hMSC腫瘤細胞趨化的下游的訊息傳導（目標 2）。 我們也將在被 動免疫裸鼠模型進一步評估使用hMSC來幫助溶瘤病毒逃避免疫系統攻擊之可行性（目 標 3）。 這些研究可提供發展以幹細胞為腫瘤治療的分子基礎 。這種結合腫瘤-基質相 互作用，溶瘤病毒和MSC誘導免疫抑制的策略提供了一種新穎且有價值的癌症標靶治 療。
Oncolytic virotherapy has made significant strides in the past decade. However, more optimization of its delivery to targeted areas is needed in order for its full therapeutic potential to be realized. Several preclinical and clinical studies using MSCs as a cell source or gene delivery vehicle have clearly demonstrated the therapeutic potential of MSCs in human diseases that offers an opportunity to overcome some of the hurdles encountered in oncolytic virotherapy delivery. The overall goal of this proposal is to understand the inextricable relationship between bone marrow-derived MSC and bone metastasizing cancer cells in promoting carcinogenesis and metastasis, and to devise a safely strategy for targeting this stromal-tumor interactions for controlling cancer metastasis. During the previous funding period, we have demonstrated several points regarding the use of hMSC in the delivery of an inducible oncolytic adenoviral vector, Ad-hOC-E1 under the control of human osteocalcin (hOC) promoter and pharmaceutical inductor vitamin D3. First, we confirmed that co-evolution of cancer-associated hMSCs with prostate cancer cells increased their ability in mesengenic differentiation as well as promotes cancer progression. Second, hMSCs preferentially migrating toward prostate cancer cells that have the property of bony metastasis, and it is dependent on IL-6 signaling through the IL-6R activation. Third, cancer-associated MSCs were more susceptible to Ad-hOC-E1 infection and the sustained viral replication upon vitamin D3 induction. This property of MSCs is critical in their use as an intermediate carrier of an oncolytic virotherapy package. Lastly, hMSCs transduced with Ad-hOC-E1 showed robust oncolysis of cancer cells in vitro, maintained their ability to migrate to established human renal cell carcinoma (RCC) xenograft tumors and improved tumor regression compared to animals treated with virus alone. after systemic administration in vivo. This impressive data demonstrated ‘‘double-edged sword’’ properties of hMSCs and raised a concern when using them for therapeutic purpose in vivo, as they have the potential to become reactive stroma and promote malignant growth. Hence, the Aims of this renewed proposal is to further understand the molecular biology that govern reactive stroma phenotype of hMSCs under the induction of bone metastatic cancer cells by characterize the direct cause-and-effect relationship between chemokine expression by cancer-associated MSCs and the cognate receptor expression on tumor cells (Aim 1); to dissect down-stream signaling that mediates IL-6/IL-6R effects in MSCs in response to tumor cells by identify the key protein kinase activation (Aim 2). Information gained from this study may provide the molecular basis for modifying MSCs for therapeutic purposes. We will also further assess the feasibility of using hMSC as novel and valuable cell-based carrier for targeted oncolytic virotherapy by their ability to help evade the protective mechanisms of the immune system in a passive immunization model in athymic nude mice, conditions analogous to those experienced by cancer patients undergoing virotherapy (Aim 3). The combination of tumor-stromal interaction, inducible oncolytic virotherapy and MSC-mediated immunusuppresion may provide a new and exciting treatment paradigm for osteotropic cancer treatment.
