PLEIOTROPHIN-- AN ANGIOGENIC SWITCH IN TUMOR PROGRESSION

本研究的长期目标是确定和表征肿瘤中多营养因子（PTN）和midkine （MK）信号新生血管（即“肿瘤血管生成”），并确定和利用治疗控制病理性血管生成和人类肿瘤的部位和方法。PTN和MK在许多侵袭性人类肿瘤中都有高表达，来自这些肿瘤的细胞系组成性地表达PTN和MK，这表明它们的表达是转化细胞中遗传稳定突变的结果。PTN转化的细胞和仅表达PTN或其c端结构域的肿瘤细胞在裸鼠体内形成高度血管性肿瘤。值得注意的是，表达PTN的细胞将碱性成纤维细胞生长因子（bFGF）释放到细胞外部位，而未转化的对照细胞则不会，这表明bFGF的释放依赖于转化，是PTN信号通路的结果。转化细胞的基本FGF释放也由PMA规定，这表明bFGF的释放依赖于活化的蛋白激酶C （PKC）异构体。这些发现可能与人类肿瘤非常相关，因为显性PTN负效应物中断内源性PTN信号传导可逆转人类乳腺癌细胞的侵袭性生长。由于PTN和MK的结构和功能具有惊人的相似性，并且这些高度相关的细胞因子的表达是许多侵袭性和高血管化肿瘤的特征，因此现在建议利用用于生成上述初步数据的模型，从功能上解剖和比较导致肿瘤促进和肿瘤血管生成的PTN和MK的不同结构域。该提案旨在确定PTN-或mk-“合作启动转化和肿瘤促进的致癌途径，确定由PTN或mk刺激的信号激活的下游基因和途径，从而导致肿瘤血管生成。寻找可能直接介导PTN和MK信号的肿瘤血管生成的因子，如活化的PKC异构体或bFGF，并确定PTN和MK信号通路中的新靶点，用于逆转人类肿瘤的逐步进展。该结果可能会确定在人类肿瘤中具有潜在广泛重要性的“血管生成开关”，促进血管生成知识的发展，并确定治疗干预的潜在位点。

The long-range goals of this research are to identify and characterize whereby pleiotrophin (PTN) and midkine (MK) signal neovascularization in tumors (i.e., "tumor angiogenesis") and to identify and exploit the sites and methods to therapeutically control pathological angiogenesis and human tumors. Both PTN and MK are highly expressed in many aggressive human tumors and cell lines from these tumors constitutively express PTN and MK, suggesting that their expression is the result of a genetically stable mutation in the transformed cell. PTN transformed cells and tumor cells in which constitutive expression of PTN or its C-terminal domain alone have been established develop highly vascular tumors in the nude mouse. Remarkably, the cells that express PTN release basic fibroblast growth factor (bFGF) to extracellular sites but non-transformed control cells do not, suggesting that bFGF release is transformation-dependent and the result of a PTN signaled pathway. Basic FGF release from transformed cells is also stipulated by PMA, suggesting that bFGF release is dependent on an activated protein kinase C (PKC) isoform. These findings may be very relevant to human tumors, since interruption of endogenous PTN signaling by a dominant negative PTN effector reverses aggressive growth of human breast cancer cells. Since there is a striking similarity of both structure and functions of PTN and MK and expression of these highly related cytokines is a feature of many aggressive and high vascularized tumors, it is mow proposed to exploit the models used to generate the Preliminary Data cited above to functionally dissect and compare the different domains of PTN and MK that lead to tumor promotion and tumor angiogenesis. The proposal seeks to define oncogenic pathways with which PTN- OR mk- "cooperates to initiate transformation and tumor promotion, to identify downstream genes and pathways which are activated by PTN or MK stimulated signaling that lead to tumor angiogenesis, to seek the factor(s) such as an activated PKC isoform or bFGF which may directly mediate PTN and MK signaled tumor angiogenesis and to define new targets in PTN and MK signaling pathways for therapies to reverse the stepwise progression of tumors in man. The results are likely to identify "angiogenic switch(s)" of potential broad importance in human tumors, advance knowledge of vasculogenesis and identify potential sites for therapeutic intervention.