miR-20b and miR-125a promote tumorigenesis in radioresistant esophageal carcinoma cells

Olaparib increases chemosensitivity by upregulating miR-125a-3p in ovarian cancer cells

OBJECTIVE

Ovarian cancer is associated with the highest mortality rate among all malignant gynecological tumors. PolyADP-ribose polymerase (PARP) inhibitor maintenance therapy is the standard treatment strategy for this type of cancer, and olaparib is a widely used oral PARP inhibitor for tumors with BRCA mutations. The present study aimed to investigate the effects of olaparib in non-BRCA-mutated ovarian cancer and the potential mechanisms involved.

METHODS

The antitumor effect of cisplatin alone or in combination with olaparib was analyzed in an ovarian cancer subcutaneous transplantation tumor model in nude mice. Furthermore, the differences in microRNA (miRNA) expression levels were analyzed using miRNA arrays. In addition, the effects of miR-125a-3p on the proliferation of non-BRCA-mutated (A2780 and OVCAR-3) ovarian cancer cells were detected using A Cell Counting Kit-8 and changes in the cell cycle were detected using flow cytometry. Furthermore, SPiDER-βGal was used to detect expression changes in cellular senescence, and the expression of DNA damage repair proteins was detected using western blot analysis.

RESULTS

The results revealed that cisplatin plus olaparib significantly reduced tumor volume in mice subjected to subcutaneous tumor transplantation, and the expression of miR-125a-3p significantly increased with this treatment combination. The overexpression of miR-125a-3p could inhibit cell migration, invasion and induces cell cycle arrest.

CONCLUSION

On the whole, the present study demonstrates that the increased expression of miR-125a-3p induces DNA damage and senescence in ovarian cancer cells, which enhances the therapeutic sensitivity.

The YTHDC1 reader protein recognizes and regulates the lncRNA MEG3 following its METTL3-mediated m6A methylation: a novel mechanism early during radiation-induced liver injury

While apoptotic cell death is known to be central to the pathogenesis of radiation-induced liver injury (RILI), the mechanistic basis for this apoptotic activity remains poorly understood. N6-methyladenosine (m6A) modifications are the most common form of reversible methylation observed on lncRNAs in eukaryotic cells, with their presence leading to pronounced changes in the activity of a range of biological processes. The degree to which m6A modification plays a role in the induction of apoptotic cell death in response to ionizing radiation (IR) in the context of RILI remains to be established. Here, IR-induced apoptosis was found to significantly decrease the levels of m6A present, with a pronounced decrease in the expression of methyltransferase-like 3 (METTL3) at 2 d post radiation in vitro. From a mechanistic perspective, a methylated RNA immunoprecipitation assay found that lncRNA MEG3 was a major METTL3 target. The expression of MEG3 was upregulated via METTL3-mediated m6A in a process that was dependent on YTHDC1, ultimately reversing the miR-20b-mediated inhibition of BNIP2 expression. Together, these findings demonstrate that the responsivity of METTL3 activity to IR plays a role in IR-induced apoptotic cell death, leading to the reverse of miR-20b-mediated BNIP2 inhibition through the YTHDC1-dependent m6A modification of MEG3, suggesting that this process may play a central role in RILI incidence.

DNA repair in tumor radioresistance: insights from fruit flies genetics

BACKGROUND

Radiation therapy (RT) is a key anti-cancer treatment that involves using ionizing radiation to kill tumor cells. However, this therapy can lead to short- and long-term adverse effects due to radiation exposure of surrounding normal tissue. The type of DNA damage inflicted by radiation therapy determines its effectiveness. High levels of genotoxic damage can lead to cell cycle arrest, senescence, and cell death, but many tumors can cope with this damage by activating protective mechanisms. Intrinsic and acquired radioresistance are major causes of tumor recurrence, and understanding these mechanisms is crucial for cancer therapy. The mechanisms behind radioresistance involve processes like hypoxia response, cell proliferation, DNA repair, apoptosis inhibition, and autophagy.

CONCLUSION

Here we briefly review the role of genetic and epigenetic factors involved in the modulation of DNA repair and DNA damage response that promote radioresistance. In addition, leveraging our recent results on the effects of low dose rate (LDR) of ionizing radiation on Drosophila melanogaster we discuss how this model organism can be instrumental in the identification of conserved factors involved in the tumor resistance to RT.

miR-378a-5p exerts tumor-suppressive effects on esophageal squamous cell carcinoma after neoadjuvant immunotherapy by downregulating APOC1/CEP55

Genetic assessment of tumors following neoadjuvant immunotherapy helps identifying targets that mediate anti-tumor immunity. In this study, we explored dysregulated RNAs in esophageal squamous cell carcinoma samples after neoadjuvant immunotherapy using deep sequencing and high-throughput screening. We identified 584 differentially expressed messenger RNAs (mRNAs), 67 differentially expressed microRNAs (miRNAs), and 1,047 differentially expressed long non-coding RNAs (lncRNAs) using differential expression analysis. Competing endogenous RNAs closely related to esophageal squamous cell carcinoma were selected via a combined Pearson's correlation test and weighted correlation network analysis. After validation using survival analysis and dry-lab and wet-lab-based studies, we identified the I-miR-378-5p-APOC1/CEP55 as a critical pathway for esophageal squamous cell carcinoma progression after neoadjuvant immunotherapy. Tumor immune infiltration analysis showed that APOC1 and CEP55 expression is associated with immune regulatory pathways and the function of multiple infiltrating immune cells. We investigated the mechanism of esophageal squamous carcinoma progression after neoadjuvant immunotherapy from the perspective of the mRNA-miRNA-lncRNA network. Furthermore, we identified accurate novel therapeutic targets and prognostic biomarkers, introduced novel perspectives to immunotherapy studies, and laid the foundation for the clinical treatment of patients with esophageal squamous carcinoma.

Non-coding RNAs in radiotherapy resistance: Roles and therapeutic implications in gastrointestinal cancer

Radiotherapy has become an indispensable and conventional means for patients with advanced solid tumors including gastrointestinal cancer. However, innate or acquired radiotherapy resistance remains a significant challenge and greatly limits the therapeutic effect, which results in cancer relapse and poor prognosis. Therefore, it is an urgent need to identify novel biomarkers and therapeutic targets for clarify the biological characteristics and mechanism of radiotherapy resistance. Recently, lots of studies have revealed that non-coding RNAs (ncRNAs) are the potential indicators and regulators of radiotherapy resistance via the mediation of various targets/pathways in different cancers. These findings may serve as a potential therapeutic strategy to overcome radiotherapy resistance. In this review, we will shed light on the recent findings regarding the functions and regulatory mechanisms of ncRNAs following radiotherapy, and comprehensively discuss their potential as biomarkers and therapeutic targets in radiotherapy resistance of gastrointestinal cancer.

Noncoding RNAs in esophageal cancer: A glimpse into implications for therapy resistance

Esophageal cancer (EC) is one of the most common malignancies of the digestive system and has a high morbidity and mortality worldwide. Chemotherapy in combination with radiotherapy is one of the most important treatment modalities for EC. Chemoradiotherapy is currently acknowledged worldwide as being the standard treatment for locally advanced or unresectable disease. Unfortunately, due to the existence of therapy resistance, a number of EC patients fail to benefit from drug or irradiation treatment, which ultimately leads to poor outcomes. Considerable efforts have been made to explore the mechanisms underlying the therapy resistance of EC. Notably, noncoding RNAs (ncRNAs), including microRNAs (miRNAs), long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs), are current research areas for the modulation of therapy responses and may serve as new targets to overcome treatment resistance in EC. Herein, we summarized the mechanisms by which ncRNAs are involved in drug and radiation resistance in EC and highlighted their role in promoting or repressing treatment resistance. Additionally, we discussed the clinical relevance of ncRNAs, which may serve as potential therapeutic targets and predictive biomarkers for EC.

The emerging role of miR-20b in human cancer and other disorders: Pathophysiology and therapeutic implications

miR-20b is a microRNA with diverse and somehow contradictory roles in the pathogenesis of human disorders, especially cancers. It has been known to be a tumor suppressor in colon cancer, renal cell carcinoma, prostate cancer, osteosarcoma and papillary thyroid cancer. In lung cancer and breast cancers, both tumor suppressor and oncogenic effects have been identified for this miRNA. Finally, in T cell leukemia, hepatocellular carcinoma, esophageal squamous cell carcinoma and cervical and gastric cancers, miR-20b is regarded as an oncogenic miRNA. In several types of cancer, dysregulation of miR-20b has been recognized as a predictive marker for patients' survival. Dysregulation of miR-20b has also been recognized in Alzheimer's disease, diabetic retinopathy, myocardial ischemia/infarction, chronic hepatitis B and multiple sclerosis. In the current review, we have summarized the miR-20b targets and related cellular processes. We have also provided a review of participation of this miRNA in different human disorders.

Melatonin Modulation of Radiation-Induced Molecular Changes in MCF-7 Human Breast Cancer Cells

Radiation therapy is an important component of cancer treatment scheduled for cancer patients, although it can cause numerous deleterious effects. The use of adjuvant molecules aims to limit the damage in normal surrounding tissues and enhance the effects of radiation therapy, either killing tumor cells or slowing down their growth. Melatonin, an indoleamine released by the pineal gland, behaves as a radiosensitizer in breast cancer, since it enhances the therapeutic effects of ionizing radiation and mitigates side effects on normal cells. However, the molecular mechanisms through which melatonin modulates the molecular changes triggered by radiotherapy remain mostly unknown. Here, we report that melatonin potentiated the anti-proliferative effect of radiation in MCF-7 cells. Treatment with ionizing radiation induced changes in the expression of many genes. Out of a total of 25 genes altered by radiation, melatonin potentiated changes in 13 of them, whereas the effect was reverted in another 10 cases. Among them, melatonin elevated the levels of PTEN and NME1, and decreased the levels of SNAI2, ERBB2, AKT, SERPINE1, SFN, PLAU, ATM and N3RC1. We also analyzed the expression of several microRNAs and found that melatonin enhanced the effect of radiation on the levels of miR-20a, miR-19a, miR-93, miR-20b and miR-29a. Rather surprisingly, radiation induced miR-17, miR-141 and miR-15a but melatonin treatment prior to radiation counteracted this stimulatory effect. Radiation alone enhanced the expression of the cancer suppressor miR-34a, and melatonin strongly stimulated this effect. Melatonin further enhanced the radiation-mediated inhibition of Akt. Finally, in an in vivo assay, melatonin restrained new vascularization in combination with ionizing radiation. Our results confirm that melatonin blocks many of the undesirable effects of ionizing radiation in MCF-7 cells and enhances changes that lead to optimized treatment results. This article highlights the effectiveness of melatonin as both a radiosensitizer and a radioprotector in breast cancer. Melatonin is an effective adjuvant molecule to radiotherapy, promoting anti-cancer therapeutic effects in cancer treatment. Melatonin modulates molecular pathways altered by radiation, and its use in clinic might lead to improved therapeutic outcomes by enhancing the sensitivity of cancerous cells to radiation and, in general, reversing their resistance toward currently applied therapeutic modalities.

Factors and molecular mechanisms of radiation resistance in cancer cells

PURPOSE

The aim of this work is to review the published studies on radiation resistance mechanisms and molecular markers involved in different tumors. The revision has been focused in the last 5 years (2016-2021).

CONCLUSIONS

Radioresistance is a cause of concern as it causes failure of radiation therapy and subsequent tumor relapse. Combination chemotherapy and radiation therapy are clinically successful in treating many types of tumors. Despite continued improvements in cancer treatment, locoregional recurrence or metastatic spread continues to occur in a high proportion of patients after being treated with radiation therapy or combination treatments. There is strong evidence that cancer stem cells contribute to radiation resistance, contributing to treatment failure. The mechanisms of radiation resistance in different tumors are not fully understood. A better understanding of cancer stem cells and the associated signaling pathways that regulate radiation resistance will open up new strategies for treating cancer by radiation therapy. Radiation can damage malignant cells mainly by the induction of DNA double strand breaks. However, in some tumors appear resistant cells that repopulate the tumor following therapy leading over time to the failure of the treatment. Native mechanisms and induced pathways, are the cause of radiation resistance. It has been described that numerous molecular markers acting through numerous mechanisms of action involved in radiation resistance, such as apoptosis resistance, alterations of cell growth, proliferation and DNA repair, hypoxia, increase in invasiveness and migration capacity, cell cycle alterations and expression of heat shock proteins, among others. Therefore, resistance to radiation is a multifactorial phenomenon that, in different cell types, it occurs through different regulatory mechanisms in which different molecules intervene. Resistance can be acquired by altering different regulatory pathways in different tumors. The knowledge of radiation resistance markers could help in the classification and treatment of patients with more aggressive tumors.