Autocrine motility factor and its receptor: Role in cell locomotion and metastasis

Summary The ability to locomote and migrate is fundamental to the acquisition of invasive and metastatic properties by tumor cells. Autocrine motility factor (AMF) is a 55 kD cytokine produced by various tumor cells which stimulates their in vitro motility and in vivo lung colonizing ability. AMF stimulates cell motility via a receptor-mediated signalling pathway. Signal transduction following binding of AMF to its receptor, a cell surface glycoprotein of 78 kD (gp78) homologous to p53, is mediated by a pertussis toxin sensitive G protein, inositol phosphate production and the phosphorylation of gp78. Cell surface gp78 is localized to the leading and trailing edges of motile cells but following cell permeabilization is found within an extended network of intracellular tubulovesicles. Gp78 tubulovesicles colocalize with microtubules and extension of the tubulovesicular network to the cell periphery is dependent on the presence of intact microtubules. Gp78 labeled vasicles can be induced to translocate between the cell center and periphery by altering intracellular pH as previously described for tubulovesicles labeled by fluid phase uptake. Anti-gp78 mAb added to viable motile cells is localized to large multivesicular bodies which, with time, relocate to the leading edge. Binding of AMF to its receptor induces signal transduction, similar to chemotactic stimulation of neutrophil mobility, as well as the internalization and transport of its receptor to the leading edge stimulating pseudopodial protrusion and cell motility.     

Autocrine motility factor receptor: a clinical review

The ability to target and alter the metastatic activity of cancer cells is a key avenue for cancer therapeutics. While local tumor control is often achieved through surgical resection, patient morbidity and mortality is dependent upon the control of regional and distant spread of disease. Autocrine motility factor receptor (AMFR) is an internalizing cell surface receptor that also exhibits ubiquitin E3 ligase activity in the endoplasmic reticulum. Stimulation of AMFR by its ligand (autocrine motility factor/phosphoglucose isomerase) alters cellular adhesion, proliferation, motility, and apoptosis. Increased AMFR expression has been reported in numerous human cancer types. Review of these studies suggests that AMFR upregulation is significantly correlated with more advanced tumor stage and decreased survival for cancer of the lung, esophagus, stomach, colon, rectum, liver and skin. AMFR has also served as an independent predictor of poor disease prognosis in these tumor types. Significant associations between AMFR expression and other clinicopathologic parameters implicated in disease progression have also been reported. Further characterization of AMFR in human cancer and the development of an understanding of the molecular regulation of this protein is critical for its future role as a target for anticancer agents.     

The TGF-beta signaling inhibitor Smad7 enhances tumorigenicity in pancreatic cancer.

Transforming growth factor-beta (TGF-beta) signaling is dependent on the heterodimerization of the type II TGF-beta receptor (TbetaRII) with the type I TGF-beta receptor (TbetaRI). Activated TbetaRI then mediates TGF-beta signals by inducing the phosphorylation of Smad2 and/or Smad3, which separately hetetorodimerize with Smad4 and translocate to the nucleus. Phosphorylation of Smad2/Smad3 by activated TbetaRI is inhibited by two newly discovered members of the Smad family, Smad6 and Smad7. We now report that Smad7 mRNA levels are increased in human pancreatic cancer by comparison with the normal pancreas, and that by in situ hybridization, Smad7 is over-expressed in the cancer cells within the tumor mass. Stable transfection of COLO-357 human pancreatic cancer cells with a full-length Smad7 construct leads to complete loss of the growth inhibitory response to TGF-beta1, without altering TGF-beta1-mediated induction of PAI-I. Furthermore, Smad7 transfected COLO-357 cells display enhanced anchorage-independent growth and accelerated growth in nude mice. These findings point to a previously unrecognized mechanism for selective suppression of TGF-beta-mediated growth inhibition in cancer cells that allows for continued activation of the PAI-I promoter by TGF-beta1, which may act to enhance the tumorigenicity of certain cancer cells.     

Leptin signaling enhances cell invasion and promotes the metastasis of human pancreatic cancer via increasing MMP-13 production

Emerging evidence has suggested that leptin, an adipokine related to energy homeostasis, plays a role in cancer growth and metastasis. However, its impact on pancreatic cancer is rarely studied. In this study, we found that leptin''s functional receptor Ob-Rb was expressed in pancreatic cancer cell lines. Treatment with leptin enhanced the migration and invasion of pancreatic cancer cells but did not affect the proliferation of human pancreatic cancer cells. Leptin up-regulated the expression of matrix metalloproteinase-13 (MMP-13) via the JAK2/STAT3 signaling pathway. The overexpression of leptin was shown to significantly promote tumor growth and lymph node metastasis in a subcutaneous model and an orthotopic model of human pancreatic cancer, respectively. Furthermore, in human pancreatic cancer tissues, the expression of Ob-Rb was positively correlated with the MMP-13 level. The increased expression of either Ob-Rb or MMP-13 was significantly associated with lymph node metastasis and tended to be associated with the TNM stage in patients with pancreatic cancer. Our findings suggest that leptin enhances the invasion of pancreatic cancer through the increase in MMP-13 production, and targeting the leptin/MMP-13 axis could be an attractive therapeutic strategy for pancreatic cancer.     

Autocrine motility factor signaling induces tumor apoptotic resistance by regulations Apaf-1 and Caspase-9 apoptosome expression

Autocrine motility factor (AMF) is a cytokine that regulates locomotion and metastasis of tumor cells. It is well known that expression levels of AMF secretion and its receptor (AMF R) are closely related to tumor malignancy and rheumatoid arthritis. We have established that AMF signaling induced anti-apoptotic activity and that human fibrosarcoma HT-1080 line that secreted high levels of AMF were resistant to drug-induced apoptosis. These cells did not express the apoptotic protease activating factor-1 (Apaf-1) and Caspase-9 genes that encode for the proteins that form the "apoptosome" complex. The disappearance of the Apaf-1 and Caspase-9 gene was recovered by a cellular signaling inhibitor of protein kinase C, phosphatidylinositol 3-phosphate kinase and mitogen-activated protein kinase of the in vitro cultured human fibrosarcoma HT-1080 line. Treatment with these inhibitors favored apoptotic cell death induced by anti-cancer drugs of the murine ascites Ehrlich line. Apoptotic resistance of tumor cells allows them to escape death from cancer chemotherapy, so an understanding of malignant anti-apoptotic activities is important. Antibodies against AMF induced Ehrlich ascites apoptosis in vitro, and effectively aided in vivo apoptosis induced by anti-cancer drugs. The results might indicate a novel route by which tumor cells protect themselves with products, such as AMF, and proliferate despite various stresses and chemical insults; AMF regulates expression of Apaf-1 and caspase-9 genes via a complex signaling pathway and indirectly regulates formation of the apoptosome.     

Autocrine motility factor receptor expression as a prognostic factor in pulmonary adenocarcinoma

Autocrine motility factor receptor (AMF-R) expression was studied immunologically in tissue specimens from 121 patients with pulmonary adenocarcinoma. AMF-R expression was correlated with lymph node metastasis and stage. The prognosis of AMF-R positive patients was poorer than that of AMF-R negative patients. Multivariate analysis showed that AMF-R expression had a significant influence on prognosis. Our findings suggest that AMF-R plays an important role in tumor progression and that AMF-R expression is a useful prognostic marker for pulmonary adenocarcinomas.     

Autocrine motility factor receptor expression associates with tumor progression in thymoma

We assessed the autocrine motility factor receptor (AMFR/gp78) expression in thymoma. AMFR/gp78 antigen was identified in tumor cells in 16 out of 51 (31.4%) thymomas. The AMFR/gp78 expression was closely associated with the stage (I/II vs. III/IV, p<0.0001), pathological subtypes (epithelial vs. other types, p=0.0214), and enhanced expression of alpha-smooth-muscle actin within stroma (p<0. 0001). The outcome of the patients with AMFR/gp78 expression was significantly worse than for those without it (p<0.01). All initial tumors with recurrence expressed AMFR/gp78. The AMFR/gp78 appears to be involved in tumor progression in thymoma.     

miR-143 inhibits the metastasis of pancreatic cancer and an associated signaling pathway

Pancreatic cancer is characterized by early metastasis and high mortality. In this study, the role of miR-143 in invasion and metastasis was investigated in pancreatic cancer cells. miR-143 expression was established by an adenovirus-carried miR-143 expression cassette. mRNA and protein levels of gene expression were examined by RT-PCR and Western blot assay, respectively. Rho GTPases activity was measured by the pull down assay. The role of miR-143 in migration and invasion of Panc-1 cells was tested in vitro. The antimetastatic effect of miR-143 was tested in a liver metastasis model, while its antitumor growth effect was tested in a xenograft Panc-1 tumor model. Results demonstrated that ARHGEF1 (GEF1), ARHGEF2 (GEF2), and K-RAS genes are the targets of miR-143. miR-143 expression significantly decreased mRNA and protein levels of GEF1, GEF2, and K-RAS genes; lowered the constitutive activities of RhoA, Rac1, and Cdc42 GTPases; decreased the protein levels of MMP-2 and MMP-9; but significantly increased the protein level of E-cadherin. miR-143 expression also significantly inhibited the migration and invasion of Panc-1 cells in vitro, liver metastasis, and xenograft tumor growth in vivo. Our study suggested that miR-143 plays a central role in the invasion and metastasis of pancreatic cancer and miR-143 is a potential target for pancreatic cancer therapy.     

Hematogenous metastasis in pancreatic cancer

Out of 248 pancreatic cancer patients, 82 with hematogenous metastases were clinicopathologically analyzed. The incidence of hematogenous metastases on laparotomy were 31% in the liver, 1.2% in the lung, and 0.4% in the adrenal gland and navel. The incidence of liver metastasis, which was present in 23% and 46% of the patients with carcinoma of the head of the pancreas and of the body and tail of the pancreas, respectively, was higher than that of carcinomas of the other digestive organs. In the autopsy findings of the cases submitted to tumor resection, early metastases to the liver, lung, cerebellum and ovary were recognized to have occurred postoperatively. A higher rate of liver metastasis with lymph node involvement in the early stage of the disease was peculiar to pancreatic cancer.     

Oridonin enhances antitumor activity of gemcitabine in pancreatic cancer through MAPK-p38 signaling pathway

Gemcitabine is currently the best treatment available for pancreatic cancer (PaCa); however, patients with the disease develop resistance to the drug over time. Agents that can either enhance the effects of gemcitabine or overcome chemoresistance to the drug are required for the treatment of PaCa. Oridonin is one such agent which is safe and multitargeted, and has been linked with the suppression of survival, proliferation, invasion and angiogenesis of cancer. In this study, we investigated whether oridonin could sensitize PaCa to gemcitabine in vitro and in vivo. In vitro, oridonin inhibited the proliferation of the PaCa cell line, BxPC-3, potentiated the apoptosis induced by gemcitabine, induced G1 cell cycle arrest and activated p38 and p53; these results were significant when oridonin was combined with gemcitabine. In vivo, we found that oridonin significantly suppressed tumor growth and this effect was further enhanced by gemcitabine (P<0.05). Tumors from nude mice injected with BxPC-3 PaCa cells and treated with a combination of oridonin and gemcitabine showed a significant upregulation in p38 and p53 activation (P<0.05 vs. control, P<0.05 vs. gemcitabine or oridonin alone). Taken together, our results demonstrate that oridonin can potentiate the effects of gemcitabine in PaCa through the mitogen-activated protein kinase (MAPK)-p38 signaling pathway, which is dependent on p53 activation.     

Autocrine and paracrine signaling through neuropeptide receptors in human cancer

Autocrine and paracrine signaling leading to stimulation of tumor cell growth is a common theme in human cancers. In addition to polypeptide growth factors such as EGF family members which signal through receptor tyrosine kinases, accumulating evidence supports the autocrine and paracrine involvement of specific neuropeptides with defined physiologic actions as neurotransmitters and gut hormones in lung, gastric, colorectal, pancreatic and prostatic cancers. These neuropeptides, including gastrin-releasing peptide, neuromedin B, neurotensin, gastrin, cholecystokinin and arginine vasopressin bind seven transmembrane-spanning receptors that couple to heterotrimeric G proteins. Studies with human small cell lung cancer (SCLC) cells support a requirement for balanced signaling through G(q) and G(12/13) proteins leading to intracellular Ca2+ mobilization, PKC activation and regulation of the ERK and JNK MAP kinase pathways. While specific neuropeptide antagonists offer promise for interrupting the single neuropeptide autocrine systems operating in pancreatic and prostatic cancers, SCLC is exemplified by multiple, redundant neuropeptide autocrine systems such that tumor growth cannot be inhibited with a single specific antagonist. However, a novel class of neuropeptide derivatives based on the substance P sequence have been defined that exhibit broad specificity for neuropeptide receptors and induce apoptosis in SCLC by functioning as biased agonists that stimulate discordant signal transduction. Thus, interruption of autocrine and paracrine neuropeptide signaling with specific antagonists or broad-spectrum biased agonists offer promising new therapeutic approaches to the treatment of human cancers.     

Hedgehog信号通路与肿瘤转移

Hedgehog(Hh)信号通路在果蝇、多种脊椎动物及人类胚胎发育过程中对细胞分化和增生起重要作用.该通路中各信号分子的突变、异常激活和过表达都可能导致肿瘤的发生.最近研究表明,Hh信号通路与多种恶性肿瘤侵袭和转移有密切的关系,其机制与肿瘤干细胞、上皮细胞间质转化、自分泌/旁分泌途径、肿瘤新生血管和淋巴管等有关.对Hh...     

Phosphoinositide 3-kinase signaling is critical for ErbB3-driven breast cancer cell motility and metastasis

Many malignancies show increased expression of the epidermal growth factor (EGF) receptor family member ErbB3 (HER3). ErbB3 binds heregulin β-1 (HRGβ1) and forms a heterodimer with other ErbB family members, such as ErbB2 (HER2) or EGF receptor (EGFR; HER1), enhancing phosphorylation of specific C-terminal tyrosine residues and activation of downstream signaling pathways. ErbB3 contains six YXXM motifs that bind the p85 subunit of phosphoinositide 3 (PI3)-kinase. Previous studies demonstrated that overexpression of ErbB3 in mammary tumor cells can significantly enhance chemotaxis to HRGβ1 and overall metastatic potential. We tested the hypothesis that ErbB3-mediated PI3-kinase signaling is critical for heregulin-induced motility, and therefore crucial for ErbB3-mediated invasion, intravasation and metastasis. The tyrosines in the six YXXM motifs on the ErbB3 C-terminus were replaced with phenylalanine. In contrast to overexpression of the wild-type ErbB3, overexpression of the mutant ErbB3 did not enhance chemotaxis towards HRGβ1 in vitro or in vivo. We also observed reduced tumor cell motility in the primary tumor by multiphoton microscopy, as well as a dramatically reduced ability of these cells to cross the endothelium and intravasate into the circulation. Moreover, whereas mutation of the ErbB3 C-terminus had no effect on tumor growth, it had a dramatic effect on spontaneous metastatic potential. Treatment with the PI3-kinase inhibitor PIK-75 similarly inhibited motility and invasion in vitro and in vivo. Our results indicate that stimulation of the early metastatic steps of motility and invasion by ErbB3 requires activation of the PI3-kinase pathway by the ErbB3 receptor.     

微小RNA与胰腺癌侵袭性转移

胰腺癌恶性侵袭转移能力很强,其机制仍未完全明确。近年来有研究发现微小RNA（miRNA）影响胰腺癌的发生发展,并与其转移密切相关。与胰腺癌转移相关的miRNA作用机制的揭示,将会为胰腺癌的治疗提供新的途径。