FOXM1-Mediated Regulation of Reactive Oxygen Species and Radioresistance in Oral Squamous Cell Carcinoma Cells.

Radioresistance is a major obstacle to the successful treatment of oral squamous cell carcinoma (OSCC). To help overcome this issue, we have developed clinically relevant radioresistant (CRR) cell lines generated by irradiating parental cells over time, which are useful for OSCC research. In the present study, we conducted gene expression analysis using CRR cells and their parental lines to investigate the regulation of radioresistance in OSCC cells. Based on gene expression changes over time in CRR cells and parental lines subjected to irradiation, forkhead box M1 (FOXM1) was selected for further analysis in terms of its expression in OSCC cell lines, including CRR cell lines and clinical specimens. We suppressed or upregulated the expression of FOXM1 in OSCC cell lines, including CRR cell lines, and examined radiosensitivity, DNA damage, and cell viability under various conditions. The molecular network regulating radiotolerance was also investigated, especially the redox pathway, and the radiosensitizing effect of FOXM1 inhibitors was examined as a potential therapeutic application. We found that FOXM1 was not expressed in normal human keratinocytes but was expressed in several OSCC cell lines. The expression of FOXM1 was upregulated in CRR cells compared with that detected in the parental cell lines. In a xenograft model and clinical specimens, FOXM1 expression was upregulated in cells that survived irradiation. FOXM1-specific small interfering RNA (siRNA) treatment increased radiosensitivity, whereas FOXM1 overexpression decreased radiosensitivity, and DNA damage was altered significantly under both conditions, as well as the levels of redox-related molecules and reactive oxygen species production. Treatment with the FOXM1 inhibitor thiostrepton had a radiosensitizing effect and overcame radiotolerance in CRR cells. According to these results, the FOXM1-mediated regulation of reactive oxygen species could be a novel therapeutic target for the treatment of radioresistant OSCC; thus, treatment strategies targeting this axis might overcome radioresistance in this disease.

The antioxidative stress regulator Nrf2 potentiates radioresistance of oral squamous cell carcinoma accompanied with metabolic modulation.

Nuclear factor erythroid 2-related factor 2 (Nrf2), which regulates the expression of critical antioxidant proteins, was recently demonstrated to play a key role in cancer progression. Resistance to radiotherapy is a major obstacle in treating oral squamous cell carcinoma (OSCC). However, little is known about the association between Nrf2 and radioresistance in OSCC. Two OSCC cell lines (SAS and HSC-2) and their clinically relevant radioresistant (CRR) clones (SAS-R, HSC-2-R) were used. The effects of Nrf2 downregulation on radiosensitivity and the involvement of glycolysis in Nrf2-mediated radioresistance were evaluated. Immunohistochemistry of phosphorylated Nrf2 (p-Nrf2) was performed in 110 patients with OSCC who underwent preoperative chemoradiotherapy and surgery. Nrf2 was stably upregulated in CRR cells in vitro and in a mouse xenograft model. Moreover, elevated Nrf2 expression was associated with radioresistance. The enhancement of Nrf2-dependent glycolysis and glutathione synthesis was involved in the development of radioresistance. Additionally, p-Nrf2 expression was closely related to the pathological response to chemoradiotherapy, and its expression was predictive of prognosis in patients with advanced OSCC. Our results suggest that Nrf2 plays an important role in the radioresistance of OSCC accompanied by metabolic reprogramming. Targeting Nrf2 antioxidant pathway may represent a promising treatment strategy for highly malignant OSCC.

Neuroprotective effect of oxytocin on cognitive dysfunction, DNA damage, and intracellular chloride disturbance in young mice after cranial irradiation.

Cranial radiation therapy (CRT) is an effective treatment for brain tumors; however, it also causes brain injuries. The pediatric brain is considered especially vulnerable compared to the adult brain; thus, brain injuries caused by CRT may severely affect their quality of life. In this study, we determined the neuroprotective effects of nasal oxytocin administration following cranial radiation in mice. We investigated the cognitive behavior of mice (novel object recognition test and novel object location test), phosphorylated histone H2AX (γ-H2AX) and K+-Cl- transporter (KCC2) by immunohistochemical analysis of the hippocampal sections, and neuronal cells by immunocytochemistry after radiation and oxytocin administration. We found that the number of γ-H2AX foci was increased, and the surface signal intensity of KCC2 immunofluorescence was decreased in cells that were irradiated with X-rays (1.5 Gy, for three consecutive days) compared with cells that were not. Furthermore, using MQAE, we found that the intracellular chloride ion concentration was downregulated in oxytocin-treated cells by increasing surface KCC2 expression. These results indicate that nasal oxytocin administration after cranial irradiation attenuates cognitive dysfunction in mice and exerts multifaceted neuroprotective effects on DNA damage and maintains chloride ion concentration in neuronal cells.

Dynamic imaging analysis reveals Auger electron-emitting radio-cisplatin induces DNA damage depending on the cell cycle.

Auger electrons can induce nanoscale physiochemical damage to DNA. The present study reports a sequential and systematic evaluation of the relationship between DNA damage such as double-strand breaks (DSBs) and the cell cycle for the Auger electron-emitting agent radiolabeled cisplatin with DNA binding ability. For dynamic imaging analysis, we used U2OS-derived cancer cells expressing two fluorescent fusion proteins: tumor-suppressor p53 binding protein 1 with a green fluorescent protein (53BP1-EGFP) and proliferating cell nuclear antigen with a red fluorescent protein (PCNA-DsRed). Time-lapse images of the cells were quantitatively analyzed using the ImageJ software with the deepImageJ plugin and the Google Colaboratory platform. From the middle-to-late G1 phase, around the G1-to-S phase transition, we found increased 53BP1 foci in cells treated with the radio-cisplatin. The radio-cisplatin caused significantly more DSBs than the nonradioactive cisplatin and saline in the G1 phase but not in the other phases. These results indicate that Auger electron-induced DNA damage, including DSBs, depends on the cell cycle. The G1 phase, which is associated with low DNA repair capacity and high radiosensitivity, is a promising target; thus, combining radiolabeled cisplatin with agents that arrest cells in the G1 phase could improve the DNA-damaging effect of Auger electrons and their therapeutic efficacy.

MiR-7-5p Is Involved in Ferroptosis Signaling and Radioresistance Thru the Generation of ROS in Radioresistant HeLa and SAS Cell Lines.

In cancer therapy, radioresistance or chemoresistance cells are major problems. We established clinically relevant radioresistant (CRR) cells that can survive over 30 days after 2 Gy/day X-ray exposures. These cells also show resistance to anticancer agents and hydrogen peroxide (H2O2). We have previously demonstrated that all the CRR cells examined had up-regulated miR-7-5p and after miR-7-5p knockdown, they lost radioresistance. However, the mechanism of losing radioresistance remains to be elucidated. Therefore, we investigated the role of miR-7-5p in radioresistance by knockdown of miR-7-5p using CRR cells. As a result, knockdown of miR-7-5p increased reactive oxygen species (ROS), mitochondrial membrane potential, and intracellular Fe2+ amount. Furthermore, miR-7-5p knockdown results in the down-regulation of the iron storage gene expression such as ferritin, up-regulation of the ferroptosis marker ALOX12 gene expression, and increases of Liperfluo amount. H2O2 treatment after ALOX12 overexpression led to the enhancement of intracellular H2O2 amount and lipid peroxidation. By contrast, miR-7-5p knockdown seemed not to be involved in COX-2 and glycolysis signaling but affected the morphology of CRR cells. These results indicate that miR-7-5p control radioresistance via ROS generation that leads to ferroptosis.

Transfer of healthy fibroblast-derived mitochondria to HeLa ρ0 and SAS ρ0 cells recovers the proliferation capabilities of these cancer cells under conventional culture medium, but increase their sensitivity to cisplatin-induced apoptotic death.

Mitochondrial dysfunction is known to contribute to cancer initiation, progression, and chemo-and radio-resistance. However, the precise role of mitochondria in cancer is controversial. Hence, here we tried to further clarify the role of mitochondria in cancer by transferring healthy mitochondria to cancer cells, and also to cells with depleted mitochondrial DNA (ρ0). Healthy mitochondria were isolated from WI-38 cells and were transferred to HeLa, SAS, HeLa ρ0, and SAS ρ0 cells. Then, cell proliferation was verified. In addition, the cells were treated by different concentrations of cisplatin and assessed for apoptosis induction and quantifying the mRNA expression of apoptosis-related genes. Results revealed that incubation of the HeLa, SAS and HeLa ρ0 cells with 5 µg/ml of the isolated mitochondria for 24 h significantly (p < 0.001) increased cell proliferation compared to non-treated controls. Interestingly, the mitochondria transfer rescued the ρ0 cells and made them capable of growing under conventional culture medium. However, the number of apoptotic cells was significantly higher in the HeLa ρ0 cells that received the mitochondria (HeLa-Fibro-Mit) compared to the HeLa ρ0. Furthermore, the expression level of BCL-2 anti-apoptotic gene was down-regulated in both HeLa-Fibro-Mit and SAS-Fibro-Mit cell lines while the expression levels of the BAX, caspase8, caspase9, and AIF pro-apoptotic genes were upregulated. Our findings indicated that although the response of cancer cells to the mitochondria transfer is cancer-type dependent, but the introduction of normal exogenous mitochondria to some cancer cells might be considered as a potential novel therapeutic strategy.

Lipid peroxidation increases hydrogen peroxide permeability leading to cell death in cancer cell lines that lack mtDNA.

4-Hydroxynonenal (HNE) is an important product of plasma membrane lipid peroxidation, which is a cause of cell and tissue injury. Mitochondrial DNA (mtDNA)-depleted ρ0 cells were established using human cervical cancer and oral squamous cell carcinoma cell lines. We investigated the effect of reactive oxygen species in ρ0 cells, especially the mechanism of hydrogen peroxide (H2 O2 )-mediated cell death. These cell were subjected to high oxidative stress and, compared with their parental cells, showed greater sensitivity to H2 O2 and high lipid peroxidation. Upregulation of HNE in the plasma membrane was observed prior to the increase in intracellular H2 O2 . The amount of oxidized lipid present changed H2 O2 permeability and administration of oxidized lipid led to further cell death after treatment with H2 O2 . Expression levels of lipoxygenase ALOX genes (ie ALOX5, ALOX12, and ALOX15) were upregulated in ρ0 cells, as were expression levels of ALOX12 and ALOX15 proteins. ALOX5 protein was mainly distributed in the nucleus, while ALOX12 and ALOX15 proteins were distributed in the nucleus and the cytoplasm. Although expression of COX2 gene was upregulated, its protein expression did not increase. ALOX (especially ALOX15) may be involved in the sensitivity of cancer cells to treatment. These data offer promise for the development of novel anticancer agents by altering the oxidation state of the plasma membrane. Our results showed that lipid peroxidation status is important for H2 O2 sensitivity and that ALOX15 is involved in lipid peroxidation status.

MiR-7-5p is a key factor that controls radioresistance via intracellular Fe2+ content in clinically relevant radioresistant cells.

MicroRNA (miRNA) is a non-coding RNA involved in regulating both cancer gene promotion and suppression. We investigated the role of miRNA in inducing radiation resistance in cancer cell lines using clinically relevant radioresistant (CRR) cells. Analysis using miRNA arrays and qPCR revealed that miR-7-5p is highly expressed in all examined CRR cells. Additionally, CRR cells lose their radioresistance when daily irradiation is interrupted for over 6 months. MiR-7-5p expression is reduced in these cells, and treating CRR cells with a miR-7-5p inhibitor leads to a loss of resistance to irradiation. Conversely, overexpression of miR-7-5p in CRR cells using a miR-7-5p mimic shows further resistance to radiation. Overexpression of miR-7-5p in parent cells also results in resistance to radiation. These results indicate that miR-7-5p may control radioresistance in various cancer cells at the clinically relevant dose of irradiation. Furthermore, miR-7-5p downregulates mitoferrin and reduces Fe2+, which influences ferroptosis. Our findings have great potential not only for examining radiation resistance prior to treatment but also for providing new therapeutic agents for treatment-resistant cancers.

Circulating miRNA-1290 as a potential biomarker for response to chemoradiotherapy and prognosis of patients with advanced oral squamous cell carcinoma: A single-center retrospective study.

MicroRNAs are a class of small, endogenous, noncoding 18- to 24-nucleotide-long RNAs that can regulate multiple processes related to cancer progression. However, their clinical value in patients with oral squamous cell carcinoma has not yet been fully explored. Therefore, the aim of this study was to investigate the clinical significance of circulating microRNAs in oral squamous cell carcinoma patients. The expression levels of circulating miR-1246 and miR-1290 in healthy volunteers and oral squamous cell carcinoma patients were examined by quantitative real-time polymerase chain reaction. The expression levels of both microRNAs in the radioresistant oral squamous cell carcinoma cell line (SAS-R) and the parent cell line (SAS) and in the conditioned medium obtained from these cell lines were also examined by quantitative real-time polymerase chain reaction. In addition, the correlations between circulating microRNA status and various clinicopathological features in 55 oral squamous cell carcinoma patients with locally advanced oral squamous cell carcinoma who underwent surgery following 5-fluorouracil-based chemoradiotherapy were examined. The expression level of miR-1290 was significantly lower in the plasma of oral squamous cell carcinoma patients than in that of healthy volunteers (p < 0.01). The expression levels of microRNAs in the conditioned medium and in the cells varied from cell to cell. In the clinicopathological analyses, the frequency of patients with low miR-1290 levels was significantly higher among cases with lower pathological differentiation and among those with a poor pathological response for preoperative chemoradiotherapy (p = 0.030 each). Furthermore, Cox regression analysis based on the 5-year overall survival and disease-free survival revealed that miR-1290 status was a significant prognostic factor for patients with oral squamous cell carcinoma (hazard ratio = 0.169, p = 0.008, and hazard ratio = 0.186, p = 0.008, respectively). Circulating miR-1290 status could be a valuable biomarker for predicting the clinical response to chemoradiotherapy as well as overall survival in patients with oral squamous cell carcinoma.

Cell Survival Effects of Autophagy Regulation on Umbilical Cord-Derived Mesenchymal Stem Cells Following Exposure to Oxidative Stress.

BACKGROUND: Due to oxidative stress, hypoxia, and serum deprivation, a large percentage of mesenchymal stem cells (MSCs) die in the early stages of transplantation. The present study aimed to address whether induction or inhibition of autophagy would affect the viability of MSCs after exposure to oxidative stress. METHODS: MSCs were isolated from umbilical cord tissue using the Ficoll gradient method. pCMV-GFP-LC-3 plasmid containing GFP-tagged LC3 was transfected into MSCs to assay autophagy level in these valuable cells. The four study groups were: MSC-LC3-Rapa, MSC-LC3-3MA, MSCs without any transfection, and MSC-GFP-LC3 (control groups). To induce autophagy, the MSC-GFP-LC3 was treated with different concentrations of Rapa for 24 hours and named MSC-LC3-Rapa. To inhibit autophagy in MSC-GFP-LC3, these cells were cultured in the presence of 3MA for 24 hours and named MSC-LC3-3MA. Non-treated MSC-GFP-LC3 and MSCs were considered as control groups. MSCs were exposed to lethal doses of H2O2 followed by cell viability evaluation with the water-soluble tetrazolium salt assay method. The data were analyzed with SPSS version 18.0 using one-way ANOVA test. P<0.05 was considered statistically significant. RESULTS: The results revealed that the enhancement of autophagy in MSC-LC3-Rapa sensitized them against oxidative stress (P=0.0006) and inhibition of autophagy in MSC-LC3-3MA led to resistance against oxidative stress (P=0.0003). CONCLUSION: Inhibition of autophagy, as a non-genetic engineering method, in MSCs enhances cell viability following exposure to the oxidative stress. This may provide a novel strategy to promote the efficiency of MSC-based cell therapy for clinical applications.

Association between radiation-induced cell death and clinically relevant radioresistance.

Radiotherapy (RT) is one of the major modalities for the treatment of human cancer and has been established as an excellent local treatment for malignant tumors. However, the existence of radioresistant cells remains one of the most critical obstacles in RT. To know the characteristics of radioresistant cells, clinically relevant radioresistant (CRR) cell lines were established. CRR cells can continue to proliferate in vitro and in vivo after exposure to 2 Gy/day of X-rays for more than 30 days. Daily microscopic observation of the irradiated CRR cells has indicated that the increase in cell death is not observed within 7 days of irradiation with 10 Gy of X-rays, suggesting that cell death is involved in cellular radioresistance. Radiation-induced regulated cell death (RCD) can be classified into three categories: apoptosis, autophagy-dependent cell death and necrosis (necroptosis). This review focuses on an aspect of radiation-induced RCD that has often been neglected: the manner in which the cells are destroyed. In many studies, apoptosis is considered the primary mode of RCD in irradiated cancer cells; however, it is necessary to consider necrosis or necroptosis as one of the modes of radiation-induced RCD.

Clinically relevant radioresistant cells exhibit resistance to H2O2 by decreasing internal H2O2 and lipid peroxidation.

Radiation therapy is one of the choices to treat malignant tumors. In radiation therapy, existence of radiation-resistant cell is a major problem to overcome. We established clinically relevant radioresistant cells that had been obtained by exposing to 2 Gy/day X-rays for more than 30 days. These cells are resistant to 2 Gy/day X-ray exposure and anticancer agents. However, the underlying resistance mechanism remains unclear. We investigated the resistance of clinically relevant radioresistant cells to hydrogen peroxide (H2O2), confirming a degree of resistance. Neither catalase enzyme activity nor aquaporins appeared to be involved in H2O2 resistance. Mitochondrial DNA copy number, adenosine triphosphate (ATP) concentration, and plasma membrane potential were decreased. The timing of H2O2 intake was delayed and lipid peroxidation was decreased. Sensitivity of clinically relevant radioresistant cells to H2O2 was enhanced by 1-palmitoyl-2-(5'-oxo-valeroyl)-sn-glycero-3-phosphocholine administration. These results suggest that the membrane status is a major factor conferring H2O2 resistance in clinically relevant radioresistant cells, and we should further investigate how membrane status could be used to enhance the therapeutic effect on cancer.

Sensitivity of mitochondrial DNA depleted ρ0 cells to H2O2 depends on the plasma membrane status.

To clarify the relationship between mitochondrial DNA (mtDNA)-depleted ρ0 cells and the cellular sensitivity to hydrogen peroxide (H2O2), we established HeLa and SAS ρ0 cell lines and investigated their survival rate in H2O2, radical scavenging enzymes, plasma membrane potential status, and chronological change in intracellular H2O2 amount under the existence of extracellular hydrogen peroxide compared with the parental cells. The results revealed that ρ0 cells had higher sensitivity to H2O2 than their parental cells, even though the catalase activity of ρ0 cells was up-regulated, and the membrane potential of the ρ0 cells was lower than their parental cells. Furthermore, the internal H2O2 amount significantly increased only in ρ0 cells after 50 µM H2O2 treatment for 1 h. These results suggest that plasma membrane status of ρ0 cells may cause degradation, and the change could lead to enhanced membrane permeability to H2O2. As a consequence, ρ0 cells have a higher H2O2 sensitivity than the parental cells.

Gene expression analyses of the small intestine of pigs in the ex-evacuation zone of the Fukushima Daiichi Nuclear Power Plant.

BACKGROUND: After the accident at the Fukushima Daiichi Nuclear Power Plant, radioactive contaminants were released over a widespread area. Monitoring the biological effects of radiation exposure in animals in the ex-evacuation zone should be continued to understand the health effects of radiation exposure in humans. The present study aimed to clarify the effects of radiation by investigating whether there is any alteration in the morphology and gene expressions of immune molecules in the intestine of pigs and inobuta (wild boar and domestic pig hybrid) in the ex-evacuation zone in 2012. Gene expression analysis was performed in small intestine samples from pigs, which were collected from January to February 2012, in the ex-evacuation zone. Pigs lived freely in this zone, and their small intestine was considered to be affected by the dietary intake of radioactive contaminants. RESULTS: Several genes were selected by microarray analysis for further investigation using real-time polymerase chain reaction. IFN-γ, which is an important inflammatory cytokine, and TLR3, which is a pattern recognize receptor for innate immune system genes, were highly elevated in these pigs. The expressions of the genes of these proteins were associated with the radiation level in the muscles. We also examined the alteration of gene expressions in wild boars 5 years after the disaster. The expression of IFN-γ and TLR3 remained high, and that of Cyclin G1, which is important in the cell cycle, was elevated. CONCLUSIONS: We demonstrated that some changes in gene expression occurred in the small intestine of animals in the ex-evacuation zone after radiation. It is difficult to conclude that these alterations are caused by only artificial radionuclides from the Fukushima Daiichi Nuclear Power Plant. However, the animals in the ex-evacuation zone might have experienced some changes owing to radioactive materials, including contaminated soil, small animals, and insects. We need to continue monitoring the effects of long-term radiation exposure in living things.

Clinically relevant radioresistant cell line: a simple model to understand cancer radioresistance.

Radiotherapy (RT) is one of the major modalities for the treatment of human cancers and has been established as an excellent local treatment for malignant tumors. Conventional fractionated RT consists of 2-Gy X-rays, fractionated once a day, 5 days a week for 5-7 weeks in total 60 Gy. The efficacy of RT depends on the existence of radioresistant cells, which remains one of the most critical obstacles in RT and radio-chemotherapy. To improve the efficacy of RT, understanding the characteristics of radioresistant cells is one of the important subjects in radiation biology. Several studies have been reported to find out molecules implicated in radioresistance. However, it is noteworthy that cellular radioresistance has been mainly studied among cells with different genetic backgrounds and different origins. Therefore, making a system to compare between radioresistant and sensitive cells with the isogenic background is required. In this review, some aspects of cellular radioresistance mainly focusing on clinically relevant radioresistant (CRR) cell lines that can continue to proliferate even under exposure to 2-Gy X-rays, once a day, for more than 30 days, which is consistent with the conventional fractionated RT are discussed.

Loss of EGF-dependent cell proliferation ability on radioresistant cell HepG2-8960-R.

Acquired radioresistance of cancer cells interferes with radiotherapy and increases the probability of cancer recurrence. HepG2-8960-R, which is one of several clinically relevant radioresistant (CRR) cell lines, has a high tolerance to the repeated clinically relevant doses of X-ray radiation. In this study, HepG2-8960-R had slightly lower cell proliferation ability than HepG2 in the presence of FBS. In particular, epidermal growth factor (EGF) hardly enhanced cell proliferation and DNA synthesis in HepG2-8960-R. Additionally, EGF could not induce the activation of Erk1/2, because the expression of EGF receptor (EGFR) protein decreased in HepG2-8960-R in accordance with the methylation of the EGFR promoter region. Therefore, cetuximab did not inhibit HepG2-8960-R cell proliferation. Our study showed that HepG2-8960-R had radioresistant and cetuximab-resistant abilities.

Guanine nucleotide-binding protein 1 is one of the key molecules contributing to cancer cell radioresistance.

Standard fractionated radiotherapy for the treatment of cancer consists of daily irradiation of 2-Gy X-rays, 5 days a week for 5-8 weeks. To understand the characteristics of radioresistant cancer cells and to develop more effective radiotherapy, we established a series of novel, clinically relevant radioresistant (CRR) cells that continue to proliferate with 2-Gy X-ray exposure every 24 h for more than 30 days in vitro. We studied three human and one murine cell line, and their CRR derivatives. Guanine nucleotide-binding protein 1 (GBP1) gene expression was higher in all CRR cells than their corresponding parental cells. GBP1 knockdown by siRNA cancelled radioresistance of CRR cells in vitro and in xenotransplanted tumor tissues in nude mice. The clinical relevance of GBP1 was immunohistochemically assessed in 45 cases of head and neck cancer tissues. Patients with GBP1-positive cancer tended to show poorer response to radiotherapy. We recently reported that low dose long-term fractionated radiation concentrates cancer stem cells (CSCs). Immunofluorescence staining of GBP1 was stronger in CRR cells than in corresponding parental cells. The frequency of Oct4-positive CSCs was higher in CRR cells than in parental cells, however, was not as common as GBP1-positive cells. GBP1-positive cells were radioresistant, but radioresistant cells were not necessarily CSCs. We concluded that GBP1 overexpression is necessary for the radioresistant phenotype in CRR cells, and that targeting GBP1-positive cancer cells is a more efficient method in conquering cancer than targeting CSCs.

The reversibility of cancer radioresistance: a novel potential way to identify factors contributing to tumor radioresistance.

To understand the molecular mechanisms responsible for radioresistance in cancer cells, we previously established clinically relevant radioresistant (CRR) cell lines from several human cancer cell lines. These CRR cells proliferate even under exposure to 2 Gy/day of X-rays for more than 30 days, which is a standard protocol for tumor radiotherapy. CRR cells received 2 Gy/day of X-rays to maintain their radioresistance (maintenance irradiation; MI). Interestingly, CRR cells that did not receive MI for more than a year lost their radioresistance, indicating that radiation-induced radioresistance is reversible. We designated these CRR-NoIR cells. Karyotyping of the parental and CRR cells revealed that the chromosomal composition of CRR cells is quite different from that of the parental cells. However, CRR and CRR-NoIR cells were more similar compared with the parental cells because CRR cells repair X-ray-induced DNA damage with higher fidelity. To identify the factor(s) involved in tumor radioresistance, previously published studies including ours have compared radioresistant cells to parental cells. In this review, we conclude that a comparison between CRR and CRR-NoIR cells, rather than parental cells, is the best way to identify factors involved in tumor radioresistance.

Mitochondria: how eminent in ageing and neurodegenerative disorders?

Numerous factors are implicated in the onset and progression of ageing and neurodegenerative disorders, with defects in cell energy supply and free radicals regulation designated as being the main functions of mitochondria and highly accentuated in plentiful studies. Hence, analysing the role of mitochondria as one of the main factors implicated in these disorders could undoubtedly come in handy with respect to disease prevention and treatment. In this review, first, we will explore how mitochondria account for neurodegenerative disorders and ageing and later will draw the various pathways contributing to mitochondrial dysfunction in their distinct way. Also, we will discuss the deviation-countering mechanisms, particularly mitophagy, a subset of autophagy known as a much larger cellular defence mechanism and regulatory system, along with its potential therapeutic effects. Last but not least, we will be highlighting the mitochondrial transfer experiments with animal models of neurodegenerative disorders.

Mitochondrial transfer in PC-3 cells fingerprinted in ferroptosis sensitivity: a brand new approach targeting cancer metabolism.

Despite recent therapeutic advancements, cancer remains one of the leading causes of death worldwide, with mitochondrial dysfunction being associated with cancer initiation and progression, along with chemotherapeutic resistance and ferroptotic cell death failure; however, the significance of mitochondria in various cancer types remains a matter of debate for the moment. The aim of this study is to ascertain the outcome of transferring healthy mitochondria into the aggressive and rapidly proliferating prostate cancer (PC-3) cells and afterwards evaluate the efficacy of combination therapy with or without the ferroptosis inducer erastin. In this sense, normal mitochondria were first isolated from human umbilical cord-derived mesenchymal stem cells, human umbilical vein endothelial cells, and human embryonic kidney cells and were later transferred into PC-3 cells and rhodamine 6G-treated PC-3 cells exhibiting mitochondrial dysfunction. Next, cell proliferation and sensitivity to cisplatin were measured using Cell Counting Kit-8 and the Malondialdehyde Assay Lipid Peroxidation Kit, respectively, along with ferroptotic damage. Transferring the healthy mitochondria into PC-3 cells was observed to increase cell proliferation and rescue the cisplatin-induced cell death, but not the erastin-induced ferroptosis, as in mitochondrial transfer effectively enhanced erastin-mediated ferroptosis in PC-3 cells. Hence, the introduction of healthy mitochondria into the highly aggressive and proliferating cancer cells would be deemed a brand new therapeutic strategy for a variety of cancers.