Lidamycin regulates p53 expression by repressing Oct4 transcription.

Antitumor antibiotic lidamycin (LDM) is widely used in the treatment of a variety of cancers. Here we demonstrated that LDM up-regulates the expression of the tumor suppressor p53 gene by repressing Oct4 transcription. We showed that low dose LDM-induced increase of p53 expression and decrease of Oct4 expression in P19 and HCT116-p53(+/+) cells. Knockdown of Oct4 expression by siRNA led to activation of p53 in both cell lines, whereas ectopical expression of Oct4 significantly inhibited p53 expression in P19 cells. LDM-induced p53 activation was blocked by ectopical expression of Oct4.

Lidamycin induces neural differentiation of mouse embryonic carcinoma cells through down-regulation of transcription factor Oct4.

Lidamycin is a potential anti-cancer drug, which is widely used in a variety of human cancer types. It has been reported that lidamycin inhibited mouse embryonic carcinoma (EC) cells growth through down-regulation of embryonic stem (ES) cell-like genes. In this study, whether 0.01 nM lidamycin induces neuronal differentiation of mouse EC cells was investigated. It was observed that lidamycin decreased transcription factor Oct4, and increased both p21 mRNA and protein expression in P19 EC cells. Furthermore, luciferase assay showed that lidamycin activated p21 promoter activity through suppression of Oct4, and Chromatin immunoprecipitation (ChIP) assay confirmed that binding of transcription factor Oct4 to the p21 promoter decreased in lidamycin-exposed cells. Knockdown of Oct4 resulted in neuron-like differentiation and up-regulation of p21 expression. In accordance, overexpression of Oct4 blocked neural differentiation and down-regulated p21 in lidamycin-treated P19 cells. Taken together, these results suggested that neuronal differentiation of EC cells induced by lidamycin was associated with the inhibition of Oct4 expression and the activation of p21 transcription. Our results have provided a novel mechanism, in which lidamycin led to cancer cell differentiation.

Inhibition of mouse embryonic carcinoma cell growth by lidamycin through down-regulation of embryonic stem cell-like genes Oct4, Sox2 and Myc.

Lidamycin (LDM, also known as C-1027) as an anti-cancer agent inhibits growth in a variety of cancer cells by inducing apoptosis and cell cycle arrest. In this study we demonstrated that inhibition of mouse embryonic carcinoma (EC) cell growth using LDM at low concentrations can be attributed to a loss of the cell's self-renewal capability but not to apoptosis or cell death, which can be correlated to the down-regulation of embryonic stem (ES) cell-like genes Oct4, Sox2 and c-Myc. MTT assays showed that LDM inhibited the growth of mouse P19 EC cells in a time- and dose-dependent manner. The EC cells exposed to a low dose (0.01 nM) of LDM lost their capability to generate colonies, as evidenced by the colony forming assay. Flow cytometer analyses demonstrated that LDM induced G1 arrest in exposed EC cells without apoptosis. Real-time qPCR, Western blotting and immunocytochemistry revealed that Oct4, Sox2 and c-Myc were down-regulated in LDM-exposed EC cells, but not adriamycin (ADM)-exposed cells. Furthermore, a combination of the low dose of LDM and ADM significantly reduced the proliferation of the cancer cells than single-agent treatment. This suggested that synergy of ADM and LDM improved chemotherapy. Taking together, our results indicate that LDM can reduce the capability for self-renewal that mouse EC cells possess through the repression of ES cell-like genes, thereby inhibiting carcinoma cell growth. This data also suggests that LDM might have potential for application in CSC-based therapy and be a useful tool for studying ES cell pluripotency and differentiation.

Lidamycin inhibits the cancer cell PKC activity induced by basic fibroblast growth factor.

AIM: To study the mechanism of inhibition of basic fibroblast growth factor (bFGF) related signal transduction by lidamycin in cancer cells. METHODS: MTT assay was used to determine the growth inhibitory effect of lidamycin (LDM) and adriamycin (ADR) in several cancer cell lines. The inhibition of bFGF bound to its receptor by LDM was measured with [125I]-bFGF binding assay. Intracellular Ca2+ stimulated by bFGF was measured by Fura-3. The formation of bFGF-receptor immune complex and the inhibitory effect of LDM on the activity of PKC isoenzymes induced by bFGF in cancer cells were identified by Western blotting analysis. RESULTS: LDM displayed extremely potent growth inhibitory effect on several cancer cell lines in a dose-dependent manner. A comparison of the IC50 values showed that the effect of LDM was 1000-fold more potent than that of ADR. LDM blocked the specific binding of [125I]-bFGF to rat lung membranes with an IC50 value of 2.0 x 10(-4) nmol x L(-1). As detected by anti-FGFR specific antibody, LDM inhibited the formation of bFGF-receptor immune complex. bFGF induced cytosolic Ca2+ response was obstructed by pretreatment with 10 nmol x L(-1) LDM. Immunoblotting demonstrated that LDM inhibited the activity of PKC isoenzymes in cancer cells stimulated with bFGF. CONCLUSION: The blocking of bFGF receptors in the signal transduction pathway may be involved in the effect of LDM on cancer cells.