Connexin 43 (Cx43), a vital gap junction protein in tumor microenvironment (TME), is a novel molecular target for melanoma chemotherapeutics due to its tumor suppressive function. Dioscin, an herbal steroidal saponin, exerts anti-tumor effects while the underlying mechanism is unclear. Using WB, FACS, and immunofluorescence methodologies, we found dioscin significantly activated the transcription and translation of Cx43 via the retinoid acid signaling pathway and simultaneously enhanced the transporting function of Cx43. Through stimulating Cx43, dioscin remarkably suppressed the migratory and invasive capacities of B16 cells, and notably decreased pluripotency markers of cancer stem cells and epithelial-to-mesenchymal transition in B16 cells and animal tumor tissues. Conversely, dioscin improved the secretion of pro-inflammatory cytokines (IL-6, TNFα, and IL-1β), and the phagocytic capacity of tumor-associated macrophages by increasing M2-to-M1 phenotype transition. More strikingly, even in Cx43 functional deficient B16 and RAW264.7 cells, dioscin still dramatically reversed the aggravated tumor malignancy and reduced macrophage phagocytic activity. Two classical metastasis animal models were utilized in vivo and results showed that dioscin showed significant anti-metastatic effects, which is closely related to the expression of Cx43 either in in situ tumor or metastatic lung nodes. In conclusion, dioscin targets Cx43 to suppress the tumor cell malignancy and activate macrophage sensitivity, thereby targeting melanoma microenvironment.
The flavonoid-based natural product genistein is a biologically active compound possessing promising anti-oxidant and anti-cancer properties. Poor pharmacokinetics along with low potency limit however the therapeutic application of genistein in cancer therapy. In order to overcome those limitations and to expand its therapeutic window of efficacy, we sought to covalently attach genistein with a heptamethine cyanine dye—IR 783—for cancer cell targeting and enhanced delivery to tumors. Herein we report the synthesis, a selective detailed characterization and preliminary in vitro/in vivo biological evaluation of genistein-IR 783 conjugate 4. The conjugate 4 displayed improved potency against human breast cancer MCF-7 cells (10.4 ± 1.0 μM) as compared with the parent genistein (24.8 ± 0.5 μM) or IR 783 (25.7 ± 0.7 μM) and exhibited selective high uptake in MCF-7 as against the normal mammary gland MCF-10A cells in various assays. In the cell viability assay, conjugate 4 exhibited over threefold lower potency against MCF-10A cells (32.1 ± 1.1 μM) suggesting that the anti-cancer profile of parent genistein is significantly improved upon conjugation with the dye IR783. Furthermore, the genistein-IR783 conjugate 4 was shown to be especially accumulated in MCF-7 cancer cells by fluorescent intensity measurements and inverted fluorescence microscopy in fixed cells as well as in live cells with time via live cell confocal fluorescence imaging. The mechanism-based uptake inhibition of conjugate 4 was observed with OATPs inhibitor BSP and in part with amiloride, as a macropinocytosis inhibitor. For the first time we have shown amiloride inhibited uptake of cyanine dye by about ~40%. Finally, genistein-IR 783 conjugate 4 was shown to be localized in MCF-7 tumor xenografts of mice breast cancer model via in vivo near infrared fluorescence (NIRF) imaging. In conclusion, conjugation of genistein with cyanine dye IR783 indeed improved its pharmacological profile by cancer cell selective uptake and targeting and therefore warrants further investigations as a new anti-cancer therapeutics derived from natural product genistein.
The results provided the first insight into the anti-angiogenesis properties of Saponin family in solid tumors and suggested a promising therapeutic potential of PSII in the ovarian cancer treatment.
The clinical applications of Rhizoma paridis in traditional Chinese medicine are well known. However, the therapeutic potential of Rhizoma paridis and its active component such as Paris saponin I (polyphyllin D) and Paris saponin II (PSII) (formosanin C) in cancer treatments have not yet been fully explored. Recent studies have demonstrated that PSII and chemoagents exhibit comparable inhibitory affects against human ovarian cancer cell growth. Since NF-κB, a ubiquitous transcription factor that plays an important role in cancer biology, is often associated with gynecological cancers, in the present study, we evaluated the possibility that PSII modulates NF-κB activity and VEGF-mediated angiogenesis and elucidated the molecular mechanisms underlying such effects. We assessed the effects of PSII on NF-κB activity in SKOV3 tumor cells and on tumor cell induced-angiogenesis using standardized angiogenesis in vitro, ex vivo and in vivo assays, western blot analysis and kinase assay. We also assessed the effect of the super-engineered repressor of IĸBα and its effect, in combination with PSII treatment on tumor growth and angiogenesis in xenograft athymic mouse models of ovarian cancer (SKOV3 and SKOV3/mutant IĸBα cells) using color Doppler ultrasound and traditional immunohistochemistry. We showed that PSII suppressed NF-κB activation as a result of the reduction in IKKβ kinase activity on its substrate IκBα and the expression of IKKβ. Compromising NF-κB activation reduced the expression of NF-κB-downstream targets such as VEGF, Bcl-2 and Bcl-xL. Such inhibitory effects at molecular levels appear to compromise tumor growth and angiogenesis. Most importantly, the combination of PSII treatment and constitutive repression of IĸBα activity exhibited marked inhibitory effects against human ovarian cancer cell growth in a xenograft mouse model of ovarian cancer. For the first time, we provide evidence showing that PSII potently inhibits angiogenesis and the growth of human ovarian cancer by suppressing NF-κB signaling.
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