Targeting the c-Met pathway potentiates glioblastoma responses to gamma-radiation.

PURPOSE: Resistance to current cytotoxic therapies limits the treatment of most solid malignancies. This results, in part, from the overactivation of receptor tyrosine kinases and their downstream pathways in tumor cells and their associated vasculature. In this report, we ask if targeting the multifunctional mitogenic, cytoprotective, and angiogenic scatter factor/hepatocyte growth factor (SF/HGF)/c-Met pathway potentiates antitumor responses to gamma-radiation. EXPERIMENTAL DESIGN: Endogenous expression of SF/HGF and c-Met was targeted in U87 MG human malignant glioma cells and xenografts using chimeric U1/ribozymes. The effects of U1/ribozymes +/- gamma-radiation on glioma cell proliferation, apoptosis, xenograft growth, and animal survival were examined. RESULTS: U1/ribozymes knocked down SF/HGF and c-Met mRNA and protein levels, sensitized cells to gamma-radiation (P < 0.005), and enhanced radiation-induced caspase-dependent cytotoxicity in vitro (P < 0.005). Intravenous U1/ribozyme therapy as liposome/DNA complexes or radiation alone modestly and transiently inhibited the growth of s.c. U87 xenografts. Combining the therapies caused tumor regression and a 40% tumor cure rate. In animals bearing intracranial xenografts, long-term survival was 0% in response to radiation, 20% in response to intratumoral adenoviral-based U1/ribozyme delivery, and 80% (P < 0.0005) in response to combining U1/ribozymes with radiation. This apparent synergistic antitumor response was associated with a approximately 70% decrease in cell proliferation (P < 0.001) and a approximately 14- to 40-fold increase in apoptosis (P < 0.0001) within xenografts. CONCLUSIONS: Targeting the SF/HGF/c-Met pathway markedly potentiates the anti-glioma response to gamma-radiation. Clinical trials using novel SF/HGF/c-Met pathway inhibitors in glioma and other malignancies associated with c-Met activation should ultimate include concurrent radiation and potentially other cytotoxic therapeutics.     

Targeting the phosphatidylinositol 3-kinase signaling pathway in breast cancer

The phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) network plays a key regulatory function in cell survival, proliferation, migration, metabolism, angiogenesis, and apoptosis. Genetic aberrations found at different levels, either with activation of oncogenes or inactivation of tumor suppressors, make this pathway one of the most commonly disrupted in human breast cancer. The PI3K-dependent phosphorylation and activation of the serine/threonine kinase AKT is a key activator of cell survival mechanisms. The activation of the oncogene PIK3CA and the loss of regulators of AKT including the tumor suppressor gene PTEN are mutations commonly found in breast tumors. AKT relieves the negative regulation of mTOR to activate protein synthesis and cell proliferation through S6K and 4EBP1. The common activation of the PI3K pathway in breast cancer has led to the development of compounds targeting the effector mechanisms of the pathway including selective and pan-PI3K/pan-AKT inhibitors, rapamycin analogs for mTOR inhibition, and TOR-catalytic subunit inhibitors. The influences of other oncogenic pathways such as Ras-Raf-Mek on the PI3K pathway and the known feedback mechanisms of activation have prompted the use of compounds with broader effect at multiple levels and rational combination strategies to obtain a more potent antitumor activity and possibly a meaningful clinical effect. Here, we review the biology of the network, its role in the development and progression of breast cancer, and the evaluation of targeted therapies in clinical trials.     

IL-6/STAT3信号传导通路及其在肿瘤靶向治疗中的作用

白细胞介素-6(IL-6)与肿瘤患者的分期、预后、转归以及对化疗药物的敏感性有关,且在患者的肿瘤组织及血清中常呈过表达.IL-6主要通过介导信号转换和转录激活因子3(STAT3)信号传导通路(IL-6/STAT3信号传导通路)来调节肿瘤细胞的增殖和分化.因此,IL-6/STAT3信号传导通路的阻断,对肿瘤具有潜在治疗意...     

Targeting the Hedgehog pathway in cancer

The Hedgehog (Hh) pathway is a major regulator of many fundamental processes in vertebrate embryonic development including stem cell maintenance, cell differentiation, tissue polarity and cell proliferation. Constitutive activation of the Hh pathway leading to tumorigenesis is seen in basal cell carcinomas and medulloblastoma. A variety of other human cancers, including brain, gastrointestinal, lung, breast and prostate cancers, also demonstrate inappropriate activation of this pathway. Paracrine Hh signaling from the tumor to the surrounding stroma was recently shown to promote tumorigenesis. This pathway has also been shown to regulate proliferation of cancer stem cells and to increase tumor invasiveness. Targeted inhibition of Hh signaling may be effective in the treatment and prevention of many types of human cancers. The discovery and synthesis of specific Hh pathway inhibitors have significant clinical implications in novel cancer therapeutics. Several synthetic Hh antagonists are now available, several of which are undergoing clinical evaluation. The orally available compound, GDC-0449, is the farthest along in clinical development. Initial clinical trials in basal cell carcinoma and treatment of select patients with medulloblastoma have shown good efficacy and safety. We review the molecular basis of Hh signaling, the current understanding of pathway activation in different types of human cancers and we discuss the clinical development of Hh pathway inhibitors in human cancer therapy.     

靶向于癌症治疗的信号通路

癌细胞以存在多种遗传上的改变为特征,这些变异的累积驱动正常细胞向侵袭性癌症进展。在癌变过程中,正常细胞转变为肿瘤细胞至少必须四到六种基因突变[1]。近年来,大量遗传学研究以及基于新一代测序技术的全基因组测序研究丰富了我们     

Targeting the Met pathway in lung cancer

Dysregulation of Met signaling has been implicated in the initiation, progression and metastasis of human cancers, and therefore represents an attractive target for anticancer drug development. Met is overexpressed in non-small-cell lung cancer and its lack of staining in normal lung tissue makes it an attractive target. To date, erlotinib and gefitinib have established themselves as first-line therapy for non-small-cell lung cancer patients whose tumors harbor an EGF receptor gene mutation, and hence, it is crucial that we identify mechanisms of resistance that could be targeted by novel agents, while keeping an acceptable toxicity profile at the same time; something very important when we develop these new drugs. Inhibitors of the Met pathway represent a therapeutic alternative in this setting. In this review, we discuss the early clinical studies reported using two Met inhibitors, a monoclonal antibody (MetMAb) and a small molecule tyrosine kinase inhibitor (MGCD265).     

Modulation of the c-Met/hepatocyte growth factor pathway in small cell lung cancer.

The c-Met receptor tyrosine kinase and its ligand HGF (hepatocyte growth factor) have been shown to be involved in angiogenesis, cellular motility, growth, invasion, and differentiation. The role of c-Met/HGF axis in small cell lung cancer (SCLC) has not been reported previously. We have determined the expression of p170(c-Met) precursor and p140(c-Met) beta-chain in seven SCLC cell lines by immunoblotting. We used the SCLC cell line H69, which expressed an abundant amount of c-Met to study the function and downstream effects of c-Met activation. Stimulation of H69 cells with HGF (40 ng/ml, 6-h stimulation) significantly altered cell motility of the SCLC cells with increased formation of filopodia and membrane ruffling, characterized as membrane blebbing, as well as increased migration of the cellular clusters were seen. We have further studied the signal transduction pathways of HGF/c-Met in the H69 cell line. The stimulation of H69 with HGF (40 ng/ml, >24 h, maximal at 1 h) increased the amount of reactive oxygen species formed by 34%. HGF stimulation (40 ng/ml, 7.5-min stimulation) of H69 cells showed increased tyrosine phosphorylated bands identified at M(r) 68,000, 120,000-140,000, and 200,000. Some of these tyrosine-phosphorylated bands were identified as the focal adhesion proteins paxillin, FAK, PYK2, and the c-Met receptor itself. Phospho-specific antibodies show that tyrosines at amino acid (a.a.) 31 of paxillin, and autophosphorylation sites at a.a. 397 of p125FAK, and a.a. 402 of PYK2 are phosphorylated in response to HGF/c-Met signaling. We also demonstrate that the Hsp90 inhibitor geldanamycin, which also affects c-Met, reduced the growth and viability of four of four SCLC cell lines by 25% to 85%, over a 72-h time period. Geldanamycin caused apoptosis of SCLC cells, as well as led to increased levels of Hsp70 but not Hsp90. These results demonstrate that c-Met/HGF pathway is functional in SCLC, and it would be useful to target this pathway toward novel therapy.     

Targeting the ubiquitin-proteasome pathway in breast cancer therapy

The ubiquitin-proteasome pathway (UPP) is the major eukaryotic mechanism for regulated intracellular proteolysis. Targeting this pathway with proteasome inhibitors has been validated as a rational strategy against hematologic malignancies, but for most solid tumor populations, including breast cancer, such agents have not shown encouraging activity. However, there is an increasing body of evidence showing that UPP dysregulation plays an important role in mammary tumorigenesis. Moreover, modulation of ubiquitin-proteasome function is emerging as a rational strategy to enhance chemosensitivity and overcome chemoresistance. Taken together, these facts suggest that we are only beginning to appreciate the relevance of this pathway for the current and future therapy of patients with breast cancer. This review provides an overview of the biology of the UPP, its role in the malignant process, the current state of knowledge regarding clinical heat shock protein and proteasome inhibition, and some likely future directions that may enhance our ability to exploit this pathway therapeutically.     

Targeting the relaxin hormonal pathway in prostate cancer

Targeting the androgen signalling pathway has long been the hallmark of anti‐hormonal therapy for prostate cancer. However, development of androgen‐independent prostate cancer is an inevitable outcome to therapies targeting this pathway, in part, owing to the shift from cancer dependence on androgen signalling for growth in favor of augmentation of other cellular pathways that provide proliferation‐, survival‐ and angiogenesis‐promoting signals. This review focuses on the role of the hormone relaxin in the development and progression of prostate cancer, prior to and after the onset of androgen independence, as well as its role in cancers of other reproductive tissues. As the body of literature expands, examining relaxin expression in cancerous tissues and its role in a growing number of in vitro and in vivo cancer models, our understanding of the important involvement of this hormone in cancer biology is becoming clearer. Specifically, the pleiotropic functions of relaxin affecting cell growth, angiogenesis, blood flow, cell migration and extracellular matrix remodeling are examined in the context of cancer progression. The interactions and intercepts of the intracellular signalling pathways of relaxin with the androgen pathway are explored in the context of progression of castration‐resistant and androgen‐independent prostate cancers. We provide an overview of current anti‐hormonal therapeutic treatment options for prostate cancer and delve into therapeutic approaches and development of agents aimed at specifically antagonizing relaxin signalling to curb tumor growth. We also discuss the rationale and challenges utilizing such agents as novel anti‐hormonals in the clinic, and their potential to supplement current therapeutic modalities.     

Hedgehog信号通路与肿瘤的关系研究进展

Hedgehog(Hh)信号通路在胚胎时期的细胞分化、组织发育及器官形成中扮演重要角色。近年来,Hh信号通路与肿瘤的关系日益受到人们的重视。多项研究结果显示Hh信号通路在多种肿瘤组织与细胞系中异常激活,并与肿瘤的增殖分化、细胞凋亡、血管新生、侵袭转移等密切相关。阻断肿瘤细胞中Hh信号传导通路将为人类肿瘤的治疗提供一个新的有效手段。     

Hedgehog信号通路与肿瘤的关系研究进展

Hedgehog（Hh）信号通路在胚胎时期的细胞分化、组织发育及器官形成中扮演重要角色。近年来,Hh信号通路与肿瘤的关系日益受到人们的重视。多项研究结果显示Hh信号通路在多种肿瘤组织与细胞系中异常激活,并与肿瘤的增殖分化、细胞凋亡、血管新生、侵袭转移等密切相关。阻断肿瘤细胞中Hh信号传导通路将为人类肿瘤的治疗提供一个新的有效手段。     

Targeting endoplasmic reticulum signaling pathways in cancer

The endoplasmic reticulum (ER) orchestrates the production of membrane-bound and secreted proteins. However, its capacity to process the synthesis and folding of protein is limited. Protein overload and the accumulation of misfolded proteins in the ER trigger an adaptive response known as the ER-stress response that is mediated by specific ER-anchored signaling pathways. This response regulates cell functions aimed at restoring cellular homeostasis or at promoting apoptosis of irreparably damaged cells. Activation or deregulation of ER-signaling pathways has been associated with various diseases including cancer. Here we discuss how tumors engage ER-signaling pathways to promote tumorigenesis and how manipulation of this process by anticancer drugs may contribute to cancer treatment.     

Targeting TGFbeta signaling for cancer therapy

Transforming growth factor (TGF) betas are multifunctional polypeptides that regulate several cellular functions, including cell growth and differentiation, extra cellular matrix production, motility and immunosuppression. The growth-inhibiting properties of TGFbeta have gained much attention into its role as a tumor suppressor. There is, however, now increasing evidence that TGFbeta switches roles, from tumor suppressor to tumor promoter, as the tumor progresses. Given the integral role of TGFbeta in the tumor progression, it follows that TGFbeta signaling offers an attractive target for cancer therapy. Several strategies including the use of antisense oligonucleotides for TGFbeta, TGFbeta antibodies, dominant negative TGFbeta receptor II, and small drug-molecules to inhibit TGFbeta receptor I kinase have shown great promise in the preclinical studies. These new findings, coupled with progressing clinical trials indicate that inhibition of TGFbeta signaling may, indeed, be a viable option to cancer therapy. This review summarizes the TGFbeta signaling, the dual role of TGFbeta--as a tumor suppressor and tumor promoter, and various strategies targeted against TGFbeta signaling for cancer therapy. The next few years promise to better our understanding of approaching cancer therapy with an eye to the inhibition of TGFbeta signaling.     

Targeting the PI3K-AKT-mTOR signaling network in cancer

The phosphoinositide 3-kinase-AKT-mammalian target of rapamycin (PI3K-AKT-mTOR) pathway is a frequently hyperactivated pathway in cancer and is important for tumor cell growth and survival. The development of targeted therapies against mTOR, a vital substrate along this pathway, led to the approval of allosteric inhibitors, including everolimus and temsirolimus, for the treatment of breast, renal, and pancreatic cancers. However, the suboptimal duration of response in unselected patients remains an unresolved issue. Numerous novel therapies against critical nodes of this pathway are therefore being actively investigated in the clinic in multiple tumour types. In this review, we focus on the progress of these agents in clinical development along with their biological rationale, the need of predictive biomarkers and various combination strategies, which will be useful in counteracting the mechanisms of resistance to this class of drugs.     

非小细胞肺癌中 HGF/c-Met 信号通路与 EGFR-TKI 获得性耐药的关系

表皮生长因子受体酪氨酸激酶抑制剂（EGFR-TKI）为首的靶向药物在晚期非小细胞肺癌患者治疗中取得巨大进展。然而,获得性耐药的出现是其不可避免的结果。肝细胞生长因子（HGF）／c-Met信号通路参与多种肿瘤细胞的形成、迁徙、血管生成等重要细胞进程。该信号通路的异常激活在EGFR-TKI 获得性耐药中发挥了重要作用。实验表明,HGF ／c-Met 信号通路抑制剂可使部分 EGFR-TKI获得性耐药患者临床获益。