Identification of an upstream region that controls the transcription of the human autocrine motility factor receptor

Expression of autocrine motility factor (AMF) and its receptor, AMFR, in human breast cancer

Autocrine motility factor (AMF) stimulates, via an autocrine route, the motility of cancer cells. The current study investigated the expression of AMF and its receptor, AMFR (gp78), in breast cancer and attempted to dissect a clinical link. Breast tumor tissues (n=120) and non-neoplastic normal tissues (n=32) were studied. AMF and AMFR distribution in tissues were assessed using immunohistochemistry and their transcripts were analyzed using RT-PCR and quantitative PCR. Median follow-up of the cohort was 10 years. Normal mammary epithelial cells, but not stromal and endothelial cells, weakly stained for AMF and AMFR. However, cancer cells showed stronger staining. Both AMF and AMFR transcripts were significantly higher in tumor than in normal tissues (p=0.003 and p=0.0001, respectively). High levels of AMF and AMFR were seen in patients who died of breast cancer (p=0.049, p=0.0435) and high AMF was also seen in patients who had local recurrence (p=0.039) compared with those who remained disease free. A significant correlation was seen between long-term survival and the AMFR:CK19 ratio, in which patients with high AMFR:CK19 ratio tumors had a significantly shorter survival (101.0 months, 80.6-121.4) compared with those with low ratio (136.0 months, 123.7-148.2), p=0.0331. In conclusion, AMF and AMFR are overexpressed in human breast cancer and are negatively associated with patients' clinical outcome. This strongly indicates that the AMF-AMFR complex plays an important role in the progression of breast cancer, as well as having a prognostic role.

Actin is closely associated with RNA polymerase II and involved in activation of gene transcription

Biochemical and morphological studies have demonstrated the presence of actin in the nucleus of different eukaryotic cells, whereas its role remains unclear. In this work, we studied the interaction and the functional relationship between nuclear actin and RNA polymerase II (RNAP II). The immunofluorescence study demonstrated a clear co-localization of nuclear actin with RNAP II in HeLa cells. Meanwhile, actin can be immunoprecipitated by anti-RNAP II antibody, indicating that they could interact with each other. Treatment of cells with alpha-amanitin induced the formation of actin bundle network in the nucleoplasm. Blocking of the formation of filamentous actin (F-actin) by cytochalasin B modified the distribution of actin. Although the actin content remained unchanged in resting and concanavalinA stimulated mouse lymphocytes, the actin content in the nuclei showed a progressive increase after stimulation. Furthermore, the antibody against actin blocked RNA synthesis in a eukaryotic in vitro transcription system. These observations implicate that nuclear actin interacts with RNAP II and may have function on the RNAP II-mediated transcription.

Correlation between loss of E-cadherin expression and overexpression of autocrine motility factor receptor in association with progression of human gastric cancers

Loss of intercellular adhesion and increased cell motility synergistically facilitate tumor cell invasion. We studied these factors in 90 patients with gastric cancers by using an immunohistochemical technique to detect strong or weak expression of E-cadherin (ECD) and autocrine motility factor receptor (AMFR). Normal gastric mucosa (control) reacted strongly for ECD and weakly for AMFR. In study cases, ECD was weak in 47 cases, and AMFR was strong in 39 cases. Weak ECD and strong AMFR expression were associated with tumor dedifferentiation. AMFR expression correlated positively with depth of invasion but not with lymph node metastasis. ECD expression correlated negatively with lymph node metastasis but not with depth of invasion. A strong inverse correlation was found between ECD and AMFR expression. Tumors with weak ECD and strong AMFR expression displayed a more aggressive phenotype than tumors with strong ECD and weak AMFR expression. The postoperative survival of patients with tumors with weak ECD and strong AMFR expression was significantly shorter than that of other groups. Since they are involved in the pathway to development of tumors with a more aggressive phenotype, ECD and AMFR should be examined to evaluate the biologic potential of gastric cancers.

The autocrine motility factor receptor gene encodes a novel type of seven transmembrane protein

Autocrine motility factor receptor (AMFR) is a cell surface glycoprotein of molecular weight 78,000 (gp78), mediating cell motility signaling in vitro and metastasis in vivo. Here, we cloned the full-length cDNAs for both human and mouse AMFR genes. Both genes encode a protein of 643 amino acids containing a seven transmembrane domain, a RING-H2 motif and a leucine zipper motif and showed a 94.7% amino acid sequence identity to each other. Analysis of the amino acid sequence of AMFR with protein databases revealed no significant homology with all known seven transmembrane proteins, but a significant structural similarity to a hypothetical protein of Caenorhabditis elegans, F26E4.11. Thus, AMFR is a highly conserved gene which encodes a novel type of seven transmembrane protein.

Tumor cell motility and metastasis : Autocrine motility factor as an example of ecto/exoenzyme cytokines

Cellular locomotion plays a critical role in such normal processes as embryonic development, tissue segregation, as well as the infiltration of fibroblasts and vascular cells during wound repair and the inflammatory responses of the adult immune system. During tumor invasion and metastasis the processes of cell migration achieve dire significance. Disruption of normal homeostatic mechanisms to benefit the survival of the individual tumor cell is a common theme discovered during the characterization of factors once thought to be tumor-specific. One such molecule, tumor cell autocrine motility factor, was so described and has only recently been identified as a normal protein involved in intracellular glycolysis as well as implicated as an extracellular effector of normal cell functions including survival of certain populations of neurons. This molecule represents a member of the newly emerging family of intracellular enzymes whose disparate functions as extracellular mediators of cellular responses defines a new class of ecto/exoenzymes which play a role in normal cellular processes and are inappropriately utilized by tumor cells to elicit new survival strategies.