Biomedical subjects

Ammar Almofti

Publications and source records attributed to Ammar Almofti.

5 recordsLinked to original sources

PubMed2004

Acquisition of lymph node, but not distant metastatic potentials, by the overexpression of CXCR4 in human oral squamous cell carcinoma.

Recently, it has been suggested that chemokine/receptor interactions determine the destination of the invasive tumor cells in several types of cancer. It has also been proposed that the stromal cell-derived factor-1 (SDF-1; CXCL12)/CXCR4 system might be involved lymph node metastasis in oral squamous cell carcinoma (SCC). In order to further clarify the role of the SDF-1/CXCR4 system in oral SCC, we generated CXCR4 stable transfectants (IH-CXCR4) using oral SCC cells, and compared them to IH, which did not express CXCR4 and which did not have lymph node metastatic potentials in vivo. We introduced enhanced green fluorescent protein (GFP) fused-CXCR4 into IH cells, and detected the GFP fluorescence in the cytoplasm and cell membrane in approximately 60% of the G418-resistant cells. This bulk-transfectant expressed a high level of CXCR4 mRNA and protein, and exhibited the characteristic calcium fluxes and chemotactic activity observed in treatment with SDF-1. SDF-1 biphasically activated extracellular signal-regulated kinase (ERK)1/2, but continuously activated Akt/protein kinase B (PKB) in IH-CXCR4 cells. Most importantly, IH-CXCR4 cells frequently metastasized to the cervical lymph node, but not to the distant organs in the orthotopic inoculation of nude mice. Furthermore, these lymph node metastases were inhibited by the treatment of a mitogen-activated protein kinase/ERK kinase inhibitor, U0126, or a phosphatidylinositol 3 kinase inhibitor, wortmannin. These results indicate that SDF-1/CXCR4 signaling mediates the establishment of lymph node metastasis in oral SCC via ERK1/2 or Akt/PKB pathway.

Animals↗

PubMed2004

The clinicopathological significance of the expression of CXCR4 protein in oral squamous cell carcinoma.

We have demonstrated the possibility that the stromal cell-derived factor-1 (SDF-1; CXCL12)/CXCR4 system might be involved in the establishment of lymph node metastasis in oral squamous cell carcinoma (SCC). In order to further clarify the role of the SDF-1/CXCR4 system in oral SCC, we examined the expression of CXCR4 and SDF-1 in biopsy specimens from 61 patients with oral SCC by means of immunohistochemistry, and investigated several clinicopathological factors, including age, sex, lymph node metastasis, invasion, recurrence and prognosis. The expression of CXCR4 and SDF-1 was observed in 57.3 and 11.4% of our subjects, respectively. Although we were unable to find a statistically significant association between the expression of SDF-1 and any clinicopathological factors, we did find a significant association between the expression of CXCR4 and lymph node metastasis (P=0.0417). Moreover, the mode of invasion (P=0.0002) and recurrence of the tumors (P=0.0185) were strongly associated with CXCR4 expression, and the CXCR4-positive group showed a significantly poorer prognosis than the CXCR4-negative group (P=0.0401). Recombinant SDF-1alpha stimulated in vitro invasiveness and scattering in CXCR4-expressing oral SCC cells, but the treatment did not affect the expression of matrix metalloproteinases or urokinase-type plasminogen activator. These results indicate that SDF-1/CXCR4 signaling in oral SCC cells might be involved in the diverse action of oral SCC, including invasion or micrometastasis at the primary site and lymph node metastasis.

Aged↗

PubMed2003

Possible role of stromal-cell-derived factor-1/CXCR4 signaling on lymph node metastasis of oral squamous cell carcinoma.

We examined the role of chemokine signaling on the lymph node metastasis of oral squamous cell carcinoma (SCC) using lymph node metastatic (HNt and B88) and nonmetastatic oral SCC cells. Of 13 kinds of chemokine receptors examined, only CXCR4 expression was up-regulated in HNt and B88 cells. CXCR4 ligand, stromal-cell-derived factor-1alpha (SDF-1alpha; CXCL12), induced characteristic calcium fluxes and chemotaxis only in CXCR4-expressing cells. CXCR4 expression in metastatic cancer tissue was significantly higher than that in nonmetastatic cancer tissue or normal gingiva. Although SDF-1alpha was undetectable in either oral SCC or normal epithelial cells, submandibular lymph nodes expressed the SDF-1alpha protein, mainly in the stromal cells, but occasionally in metastatic cancer cells. The conditioned medium from lymphatic stromal cells promoted the chemotaxis of B88 cells, which was blocked by the CXCR4 neutralization. SDF-1alpha rapidly activated extracellular signal-regulated kinase (ERK)1/2 and Akt/protein kinase B (PKB), and their synthetic inhibitors attenuated the chemotaxis by SDF-1alpha. SDF-1alpha also activated Src family kinases (SFKs), and its inhibitor PP1 diminished the SDF-1alpha-induced chemotaxis and activation of both ERK1/2 and Akt/PKB. These results indicate that SDF-1/CXCR4 signaling may be involved in the establishment of lymph node metastasis in oral SCC via activation of both ERK1/2 and Akt/PKB induced by SFKs.

Animals↗

PubMed2003

Cationic liposome-mediated gene delivery: biophysical study and mechanism of internalization.

To identify factors affecting cationic liposome-mediated gene delivery efficiency, we studied the relationship between the biophysical characteristics of liposome/DNA complexes (lipoplexes) at different (+/-) charge ratios, their structures as monitored by atomic force microscopy (AFM), and their mechanism(s) of internalization into the cells. Significant changes were observed in the particle size and zeta potential of liposomes and their structures assessed by AFM upon addition of DNA, which depended on (+/-) charge ratios. AFM images showed that lipoplexes were formed from extensively fused and apparently homogeneous lipid particles encapsulating DNA. Lipoplexes were found to internalize the cells through the endocytosis pathway. Lipoplex-cell fusion was found to occur mainly at the plasma membrane level; however, this lipoplex-cell membrane fusion was found to be essential for the uptake of the large particles. A new perspective for the internalization of large lipoplex particles into cytoplasm is discussed.

Biophysical Phenomena↗

PubMedDate not supplied

Lipoplex size determines lipofection efficiency with or without serum.

In order to identify factors affecting cationic liposome-mediated gene transfer, the relationships were examined among cationic liposome/DNA complex (lipoplex)-cell interactions, lipoplex size and lipoplex-mediated transfection (lipofection) efficiency. It was found that lipofection efficiency was determined mainly by lipoplex size, but not by the extent of lipoplex-cell interactions including binding, uptake or fusion. In addition, it was found that serum affected mainly lipoplex size, but not lipoplex-cell interactions, which effect was the major reason behind the inhibitory effect of serum on lipofection efficiency. It was concluded that, in the presence or absence of serum, lipoplex size is a major factor determining lipofection efficiency. Moreover, in the presence or absence of serum, lipoplex size was found to affect lipofection efficiency by controlling the size of the intracellular vesicles containing lipoplexes after internalization, but not by affecting lipoplex-cell interactions. In addition, large lipoplex particles showed, in general, higher lipofection efficiency than small particles. These results imply that, by controlling lipoplex size, an efficient lipid delivery system may be achieved for in vitro and in vivo gene therapy.

Cations↗