The terminal differentiation of malignant melanoma cells is known to be induced by activating cAMP signaling pathway with alpha-MSH or cAMP analogues. However, sustained activation of cAMP signaling system that induces the differentiation of melanoma cells, also induces the desensitization of the pathway at the receptor level. Nevertheless, the adaptation of adenylate cyclase (AC) expression by sustained activation of cAMP signaling system has not been clearly understood. This study was performed to examine whether the sustained activation of cAMP system induce changes in the expression AC isoforms as an adaptation mechanism. Treatment of B16/F10 murine melanoma cells with 100 mM forskolin for 6 days resulted in differentiation, melanin accumulation and increased expression of tyrosine hydroxylase mRNA. In the forskolin-treated melanoma cells, change in expression of various AC isoform at the transcription level was detected by reverse-transcription polymerase chain reaction (RT-PCR). Expression of AC isoform mRNA: ACI, III, VI, VII, and IX increased to the level of 196-392% of the control whereas the level of ACII was decreased by 30%. The cAMP concentration was increased both in basal and alpha-MSH stimulated cells, but the AC activity was decreased in the forskolin treated cells. Thus, these results suggest that sustained activation of cAMP system induces differential expression of AC isoforms, which results in increase of cAMP accumulation.
Adenylate Cyclase/*genetics ; Animal ; Cell Differentiation ; Cyclic AMP/*metabolism ; Forskolin/*pharmacology ; Isoenzymes/genetics ; Melanoma, Experimental/*enzymology/*pathology ; Mice ; Signal Transduction

Increasing evidence suggests that stress may induce changes in hair color, with the underlying mechanism incompletely understood. In this study, female C57BL/6 mice subjected to electric foot shock combined with restraint stress were used to build chronic stress mouse model. The melanin contents and tyrosinase activity were measured in mouse skin and B16F10 melanoma cells. The enzyme-linked immunosorbent assay (ELISA) was used to determine the content of tumor necrosis factor α (TNF-α), interleukin- 1β (IL-1β) and interleukin-6 (IL-6) in the mouse skin. The content of nuclear factor κB (NFκB)/p65 subunit in mouse skins was valued by immunofluorescence staining. The results demonstrated that under chronic stress, the fur color turned from dark to brown in C57BL/6 mice due to the decrease of follicle melanocytes and tyrosinase activity in C57BL/6 mouse skin. Simultaneously, inflammatory responses in skins were detected as shown by increased NFκB activity and TNF-α expression in stressed mouse skin. In cultured B16F10 melanoma cells, TNF-α reduced the melanogenesis and tyrosinase activity in a dose-dependent manner. These findings indicate that chronic stress induces fur color change by decreasing follicle melanocytes and tyrosinase activity in female C57BL/6 mice, and TNF-α may play an important role in stress-induced hair color change.
Animal Fur ; Animals ; Color ; Female ; Melanins ; Melanocytes ; enzymology ; Melanoma, Experimental ; Mice ; Mice, Inbred C57BL ; Monophenol Monooxygenase ; metabolism ; Pigmentation ; Skin ; physiopathology ; Stress, Physiological

Glycyrrhizin (GR), triterpenoid saponin composed of one glycyrrhetinic acid (GA) and two glucuronic acids, is a main constituent of the hydrophilic fraction of licorice (Glycyrrhiza glabra) extracts and is known to have a wide range of pharmacological actions. In this study, we investigated the mechanism of GR effect on melanogenesis in B16 murine melanoma cells. The cellular levels of tyrosinase mRNA, protein, enzyme activities and melanin contents were increased by GR in a dose dependent manner. Expression of tyrosinase-related protein-2 (TRP-2) mRNA was also increased by GR, however, no significant change was observed on TRP-1. No cytotoxicity was observed at the effective concentration range of GR. GA showed no effect on melanogenesis at the equivalent nontoxic concentrations, indicating that glycoside structure is important in the stimulatory effect of GR on melanogenesis. These results indicate that GR-induced stimulation of melanogenesis is likely to occur through the transcriptional activation.
Animal ; Blotting, Western ; Glycyrrhetinic Acid/pharmacology ; Glycyrrhizic Acid/*pharmacology ; Intramolecular Oxidoreductases/genetics/metabolism ; Melanins/*biosynthesis ; Melanoma, Experimental/enzymology/*metabolism ; Mice ; Monophenol Monooxygenase/genetics/metabolism ; Proteins/genetics/metabolism ; Reverse Transcriptase Polymerase Chain Reaction

Malignant melanoma still remains to be a serious health threat. Overexpression of focal adhesion kinase (FAK) in melanoma has suggested that FAK could be a promising target for therapeutic intervention. To further investigate the function of FAK in melanoma, FAK expression was down-regulated by stable transfection of plasmid harboring FAK small interfering RNA (siRNA) into melanoma cell line. Two stable cell lines, F10-siFAK and F10-control, have been constructed and screened. Compared with the F10-control, both the mRNA and protein levels of FAK decreased significantly, and the cell cycle of F10-siFAK was arrested at G1 phase. Furthermore, the tumor growth rate of F10-siFAK cells was notably slower than that of F10-control in in vivo tumor models. These results show that FAK is an important regulatory gene in melanoma. The stable FAK-knockdown melanoma cell line is an useful tool for further investigation of FAK's function in the progression of melanoma, and also an effective means of drug screening for anti-melanoma therapeutics.
Animals ; Cell Cycle ; Cell Line, Tumor ; Cell Proliferation ; Down-Regulation ; Focal Adhesion Protein-Tyrosine Kinases ; genetics ; metabolism ; G1 Phase ; Gene Knockdown Techniques ; Melanoma, Experimental ; enzymology ; pathology ; Mice ; Mice, Inbred C57BL ; Mitogen-Activated Protein Kinase 1 ; metabolism ; Mitogen-Activated Protein Kinase 3 ; metabolism ; Plasmids ; RNA, Messenger ; metabolism ; RNA, Small Interfering ; genetics ; Transfection

OBJECTIVETo investigate the effects of endostatin and doxycycline on microcirculation patterns in melanoma and their molecular mechanisms.

METHODSTo establish mouse B16 melanoma model by subcutaneous injection of B16 melanoma cell suspension. The mice were divided into 3 experimental groups and 1 control group. To treat the mice in the 3 experimental groups with endostatin, doxycycline, endostatin and doxycycline, respectively, and the control group without any treatment. The tumor volume was measured and recorded to make comparison of their growth rate. To assess the expression of MMP-2, MMP-9 and TIMP-2 by immunohistochemical staining. The three microcirculation patterns of endothelium-dependent vessels, mosaic vessels and vasculogenic mimicry were counted. The activity of MMP-2, MMP-9 between different groups was examined by gelatin zymography.

RESULTSTumor growth in the three experimental groups was statistically significantly slower than that in the control group. The expression of MMP-2, MMP-9 and TIMP-2 in each treated group was significantly different with that in the control group. The amount of three microcirculation patterns in three experimental groups was less than that of the control group, and the amount of MV and VM in each experimental group was significantly less than that in the control group. By gelatin zymography, the enzyme activity of MMP-9, actived-MMP-2 and MMP-2/proMMP-2 in ES, DOX and ES + DOX group was lower than that in the control group, but the enzyme activity of pro-MMP-2 among the four groups was not significantly different.

CONCLUSIONThe combined use of doxycycline and endostatin in melanoma can inhibit the expression of MMPs, influencing the formation of different microcirculation patterns in melanoma.

Animals ; Antineoplastic Agents ; pharmacology ; Cell Line, Tumor ; Doxycycline ; pharmacology ; Drug Combinations ; Drug Synergism ; Endostatins ; pharmacology ; Female ; Male ; Matrix Metalloproteinase 2 ; metabolism ; Matrix Metalloproteinase 9 ; metabolism ; Melanoma, Experimental ; blood supply ; enzymology ; pathology ; Mice ; Mice, Inbred C57BL ; Microcirculation ; drug effects ; Microvessels ; pathology ; Neoplasm Transplantation ; Tissue Inhibitor of Metalloproteinase-2 ; metabolism ; Tumor Burden ; drug effects