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Abstract [Objective] In order to optimize the efficient virus elimination and regeneration system from shoot apical meristem of tea chrysanthemum, suitable heat treatment duration and detoxification agents, this study aims to improve the problem of low virus-free seedlings obtaining ratio. [Methods] Six tea chrysanthemum varieties were used as materials. The axenic seedlings were pre-treated with alternating heat temperature treatment of 40 ℃/32 ℃ day/night, detoxification agents such as salicylic acid, ribavirin, and abscisic acid, as well as a combination of detoxification agents and heat treatment. The rate of callus induction, regeneration frequency, and average number of regenerated shoots from inoculated shoot apical meristems were compared among different treatment methods, the detoxification efficacy of various treatments were evaluated. [Results] There was a significant difference in the regeneration frequency of shoot apical meristems among different varieties of tea chrysanthemum, with ‘Wuyuan Huangju’ having the highest regeneration frequency of 54.77%. Under different heat treatment days, the difference in regeneration of shoot apical meristems in tea chrysanthemum reached a significant level, with ‘Hangbaiju’ and ‘Qiyuexue’ showing the best regeneration after 40 ℃/32 ℃ heat treatment. Salicylic acid, ribavirin, and abscisic acid treatments inhibited the regeneration of shoot apical meristems. Salicylic acid and ribavirin treatments combined with heat treatment promoted the regeneration of shoot apical meristems, while high concentration abscisic acid combined with heat treatment severely inhibited the regeneration of shoot apical meristems. Treatment with 10 μmol/L salicylic acid combined with heat treatment showed the best regeneration. Virus-free seedlings were obtained through suitable heat treatment combined with detoxification agents. [Conclusion] The combination of 10 μmol/L salicylic acid with 40 ℃/32 ℃ day/night pretreatment for 40 days significantly enhances the regeneration frequency of shoot apical meristems, and obtains virus-free seedlings

Simple Summary: Long non-coding RNAs have been demonstrated to play important roles in regulating tumor development and progression in breast cancer, which is tumor type dependent and cellular localization dependent. However, the regulatory mechanisms remain unclear. Herein, we found a dual function of long non-coding RNA CCAT2 in the luminal subtype of breast cancer, depending on its subcellular distribution. CCAT2 showed an overall downregulation in the tumor tissues from the luminal breast cancer patients. Cytoplasmic CCAT2 in the luminal subtype of breast cancer cell MCF-7 or T47D significantly suppressed cell proliferation and cancer cell stemness in vitro. It inhibited tumor growth in vivo, which was mediated with miR-221-p27 signaling. In contrast, nuclear overexpression of CCAT2 led to upregulation of OCT4-PG1 and the induction of cancer cell stemness. In summary, for the first time, the current study revealed a dual function of lncRNA CCAT2 as a tumor suppressor or oncogene depending upon its subcellular distribution. Breast cancer is the most common cancer in women around the world. Emerging evidence has indicated the important roles that non-coding RNAs play in regulating tumor development and progression in breast cancer. Herein, we found a dual function of long non-coding RNA (LncRNA) CCAT2 in the luminal subtype of breast cancer, depending on its subcellular distribution. CCAT2 showed an overall downregulation in the tumor tissues from luminal breast cancer patients. Transient overexpression of CCAT2 in the luminal subtype of breast cancer cell MCF-7 or T47D significantly suppressed cell proliferation in vitro and inhibited tumor growth in vivo. Gene expression analysis of cancer stem cell markers including OCT4, NANOG, h-TERT, SOX2 and KLF4; flow cytometry analysis of breast cancer stem cell population, and mammosphere formation assay demonstrated inhibition of cancer cell stemness with transient transfection of CCAT2 in which exogenous CCAT2 mainly distributed in the cytoplasm and regulated miR-221-p27 signaling via RNA sequence interaction. However, overexpression of CCAT2 in MCF-7 cells through pMX retroviral nuclear expression vector accumulated CCAT2 in the nucleus, leading to upregulation of OCT4-PG1, a pseudogene of stem gene OCT4, thereby promoting the cancer cell stemness. In conclusion, the current study, for the first time, revealed a dual function of lncRNA CCAT2 as a tumor suppressor or oncogene depending upon its subcellular distribution. It also demonstrated the regulatory mechanism of cytoplasmic CCAT2 in suppressing tumorigenesis in the luminal subtype of breast cancer. [ABSTRACT FROM AUTHOR]

P-element-induced wimpy testis (Piwi)-interacting RNAs (piRNAs) are a class of germline-enriched small non-coding RNA that associate with Piwi family proteins and mostly induce transposon silencing and epigenetic regulation. Emerging evidence indicated the aberrant expression of Piwil proteins and associated piRNAs in multiple types of human cancer including breast cancer. Although the majority of piRNAs in breast cancer remains unclear of the function mainly due to the variety of regulatory mechanisms, the potential of piRNAs serving as biomarkers for cancer diagnosis and prognosis or therapeutic targets for cancer treatment has been demonstrated by in vitro and in vivo studies. Herein we summarized the research progress of oncogenic or tumor suppressing piRNAs and their regulatory mechanisms in regulating human breast cancer, including piR-021285, piR-823, piR-932, piR-36712, piR-016658, piR-016975 and piR-4987. The challenges and perspectives of piRNAs in the field of human cancer were discussed. [ABSTRACT FROM AUTHOR]

Cisplatin has been widely used in the treatment of a various types of cancers including triple-negative breast cancer (TNBC) by damaging DNA and inducing apoptosis. However, its anti-cancer effects are often limited due to chemo-resistance, which is one of the main reasons causing cancer relapse and metastasis. To overcome resistance, cisplatin is often used in combination with other drugs or molecules. Our study found that the targeted inhibition of miR-221/222 in MDA-MB-231 cells promoted cisplatin-induced cell apoptosis, and increased the cell sensitivity to cisplatin in vitro. Much higher expression levels of miR-221/222 were detected in the cisplatin-resistant MDA-MB-231 cells and in cisplatin-resistant breast cancer patients. The combination chemotherapy of cisplatin with anti-miR-221/222 showed much higher efficiency in suppressing tumor growth in the mice transplanted with MDA-MB-231 cells. In addition, anti-miR-221 and anti-miR-222 showed synergetic effects on improving sensitivity to cisplatin in MDA-MB-231 cells. Suppression of SOCS1-STAT3-Bcl-2 pathway and activation of p53-Pten signaling both contribute to anti-miR-221/222-induced sensitivity to cisplatin in MDA-MB-231 cells. These findings suggest the potential of a novel approach for the combination chemotherapy of cisplatin with small non-coding RNA in treatment of human TNBC. [ABSTRACT FROM AUTHOR]

Triple-negative breast cancers (TNBC) are more aggressive due to lacking receptors for hormone therapy and maintaining stemness features in cancer cells. Herein we found long non-coding RNA CCAT2 overexpressed specially in TNBC, and in breast cancer stem cells (BCSC) as well. Enforced overexpression and targeted knockdown demonstrated the oncogenic function of CCAT2 both in vitro and in vivo. CCAT2 promoted the expression of stemness markers including OCT4, Nanog and KLF4, increased mammosphere formation and induced ALDH+ cancer stem cell population in TNBC. A chromosomally adjacent gene OCT4-PG1, as a pseudogene of OCT4, was upregulated by CCAT2, and positively regulated the stemness features of TNBC cells. miR-205 was identified as a target gene of CCAT2 in TNBC. Point-mutation in CCAT2 impaired the sponge inhibition of miR-205. Overexpression of miR-205 rescued the oncogenic phenotypes induced by CCAT2. In addition, Notch2, as a target gene of miR-205, was downregulated by miR-205 and upregulated by CCAT2 in TNBC. Collectively, the current study revealed a novel function of CCAT2 in promoting tumor initiation and progression in TNBC through upregulating OCT4-PG1 expression and activating Notch signaling. These findings not only demonstrated a lncRNA-based therapeutic strategy in treatment of TNBC, but also added a node to the regulatory network of CCAT2 that controls aggressiveness of breast cancer stem cells. [ABSTRACT FROM AUTHOR]