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Despite its low transfer efficiency, suicide gene therapy with HSV-TK is known for its bystander killing effect. The connexin-based gap junction is believed to mediate the bystander effect. Recently, we found that resveratrol, a polyphenol compound, increased the expression of Cx26 and Cx43, which are connexins and important constituents of gap junctions, in murine hepatoma cells. Hypothetically, the resveratrol-induced upregulation of gap junctions may improve the bystander effect that HSV-TK/GCV has on hepatoma cells. Our present investigation revealed that resveratrol could enhance intercellular communication at the gap junctions in CBRH7919 hepatoma cells and thereby enhance the bystander killing effect of GCV on CBRH7919TK cells. However, inhibition of gap junction using its long-term inhibitor alpha-glycyrrhetinic acid had a negative influence on the bystander effect of gene therapy with HSV-TK/GCV. In addition, combined resveratrol and GCV treatment in tumor-bearing mice with CBRH7919TK and CBRH7919WT cells at a ratio of 2:3 resulted in a significant decrease in the volume and weight of the tumor in comparison to GCV or only resveratrol. The present results demonstrate that resveratrol can enhance the bystander effect exerted by the HSV-TK/GCV system by enhancing connexin-mediated gap junctional communication. [ABSTRACT FROM AUTHOR]

Berberine (BBR), a natural alkaloid derived from Coptis, has anticancer activity. Some researchers have found that it could restrain epithelial-mesenchymal transition (EMT) of melanoma, neuroblastoma, and other tumor cells. However, it is unclear whether BBR can reverse EMT in hepatocellular carcinoma (HCC) and gastric carcinoma (GC). In our study, BBR inhibited the migration and invasion of HepG2, MGC803, and SGC7901 cells in a dose-dependent manner. Transcription sequencing assays showed that Vimentin, MMP, and Smad3 were downregulated, but Smad2, Smad6, TAB2, ZO-1, and claudin 7 were upregulated when treated with BBR. GO Enrichment analysis of KEGG pathway showed that BBR significantly inhibited TGF- β /Smad at 12 h, then, PI3K/Akt and Wnt/ β -catenin signaling pathways at 24 h, which were closely related to the proliferation, migration, and EMT. The results of the transcriptome sequencing analysis were verified by Western Blot. It showed that the expression of epithelial marker E-cadherin and ZO-1 remarkably augmented with BBR treatment, as well as declined mesenchymal markers, including N-cadherin and Vimentin, decreased transcription factor Snail and Slug. The effects of BBR were similar to those of the PI3K inhibitor LY294002 and TGF- β receptor inhibitor SB431542. Furthermore, β -catenin and phosphorylation of AKT, Smad2, and Smad3 were changed dose-dependently by BBR treatment, which upregulated p-Smad2 and downregulated the others. Combined with LY or SB, respectively, BBR could enhance the effects of the two inhibitors. Simultaneously, IGF-1 and TGF- β , which is the activator of PI3K/AKT and TGF- β /Smad, respectively, could reverse the anti-EMT effect of BBR. The Molecular Docking results showed BBR had a high affinity with the TGF- β receptor I (TGF β R1), and the binding energy was -7.5 kcal/mol, which is better than the original ligand of TGF β R1. Although the affinity of BBR with TGF- β receptor II (TGF β R2) was lower than the original ligand of TGF β R2, the more considerable negative binding energy (-8.54 kcal/mol) was obtained. BBR upregulated p-Smad2, which was different from other reports, indicating that the function of Smad2 was relatively complex. Combination BBR with SB could enhance the effect of the inhibitor on EMT, and the results indicated that BBR binding to TGF β R was not competitive with SB to TGF β R since different binding amino acid sites. Our experiments demonstrated BBR increased p-Smad2 and decreased p-Smad3 by binding to TGF β R1 and TG β FR2 inhibiting TGF- β /Smad, then, PI3K/AKT and other signaling pathways to restrain EMT, metastasis, and invasion in tumor cells. The effect of BBR was similar on the three tumor cells., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Haiyan Du et al.)

Suicide gene therapy is a promising strategy against melanoma. However, the low efficiency of the gene transfer technique can limit its application. Our preliminary data showed that dioscin, a glucoside saponin, could upregulate the expression of connexins Cx26 and Cx43, major components of gap junctions, in melanoma cells. We hypothesized that dioscin may increase the bystander effect of herpes simplex virus thymidine kinase/ganciclovir (HSV-tk/GCV) through increasing the formation of gap junctions. Further analysis showed that dioscin indeed could increase the gap junctional intercellular communication in B16 melanoma cells, resulting in more efficient GCV-induced bystander killing in B16tk cells. By contrast, overexpression of dominant negative Cx43 impaired the cell-cell communication of B16 cells and subsequently weakened the bystander effect of HSV-tk/GCV gene therapy. In vivo, combination treatment with dioscin and GCV of tumor-bearing mice with 30% positive B16tk cells and 70% wild-type B16 cells caused a significant reduction in tumor volume and weight compared to treatment with GCV or dioscin alone. Taken together, these results demonstrated that dioscin could augment the bystander effect of the HSV-tk/GCV system through increasing connexin-mediated gap junction coupling.

Objectives: This study aimed to investigate the precise role of miR-34b in nasopharyngeal carcinoma (NPC)., Materials and Methods: The expression of miR-34b and transcription of ubiquitin-specific peptidase 22 (USP22) were examined using quantitative reverse transcription-polymerase chain reaction. Western blot analysis was used to measure the protein expression of USP22. A dualluciferase assay was used to investigate the interaction between miR-34b and USP22. Cell viability was determined by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide assay. The cell cycle was analyzed by propidium iodide staining followed by flow cytometry analysis., Results: miR-34b was significantly downregulated in NPC tissues and NPC cell lines. Overexpression of miR-34b in NPC SUNE-6-10B cells inhibited cell viability and proliferation. USP22 was highly expressed in NPC cells and promoted cell viability and proliferation. Restoration of USP22 expression could reverse the effect of miR-34b on NPC cell viability and proliferation., Conclusion: miR-34b acts as a tumor suppressor in NPC, which is mediated via repression of the oncogene USP22.