Radiosensitivity Of Cancer Cells Research Articles

Self‐Assembled Peptide‐Gold Nanoclusters with SiRNA Targeting Telomeric Response to Enhance Radiosensitivity in Lung Cancer Cells

Lung cancer cells resistant to radiotherapy present a significant clinical challenge. Stable telomeric structures, maintained by the TRF2 protein, play a critical role in protecting cells from ionizing radiation. Reduced TRF2 expression increases DNA damage and radiosensitivity. We designed a self‐assembling system utilizing ultra‐small luminescent gold nanoclusters (AuNCs) with radiosensitizing properties, combined with siRNA targeting TRF2. The system forms ≈100 nm non‐spherical structures with AuNCs enriched in the outer layer, exhibiting a 17.6‐fold enhancement in red photoluminescence due to aggregation‐induced effects. This nanoplatform efficiently penetrates lung cancer cells, reducing TRF2 expression by 50%. Under 5 Gy radiotherapy, cells treated with this system show a 1.5‐fold radiosensitivity increase from AuNCs and a 2.3‐fold reduction in clonogenic survival due to telomere deprotection. The AuNC‐siRNATRF2 system combines enhanced optical properties with biological functionality, offering a promising approach to augment radiotherapy efficacy by disrupting telomeric protective mechanisms in cancer cells.

Enhancing the radiosensitivity of colorectal cancer cells by reducing spermine synthase through promoting autophagy and DNA damage

BACKGROUND Colorectal cancer (CRC), the third most common cancer worldwide, has increasingly detrimental effects on human health. Radiotherapy resistance diminishes treatment efficacy. Studies suggest that spermine synthase (SMS) may serve as a potential target to enhance the radiosensitivity. AIM To investigate the association between SMS and radiosensitivity in CRC cells, along with a detailed elucidation of the underlying mechanisms. METHODS Western blot was adopted to assess SMS expression in normal colonic epithelial cells and CRC cell lines. HCT116 cells were transfected with control/SMS-specific shRNA or control/pcDNA3.1-SMS plasmids. Assessments included cell viability, colony formation, and apoptosis via MTT assays, colony formation assays, and flow cytometry. Radiosensitivity was studied in SMS-specific shRNA-transfected HCT116 cells post-4 Gy radiation, evaluating cell viability, colony formation, apoptosis, DNA damage (comet assays), autophagy (immunofluorescence), and mammalian target of rapamycin (mTOR) pathway protein expression (western blot). RESULTS Significant up-regulation of SMS expression levels was observed in the CRC cell lines. Upon down-regulation of SMS expression, cellular viability and colony-forming ability were markedly suppressed, concomitant with a notable increase in apoptotic indices. Furthermore, attenuation of SMS expression significantly augmented the sensitivity of HCT116 cells to radiation therapy, evidenced by a pronounced elevation in levels of cellular DNA damage and autophagy. Importantly, down-regulation of SMS corresponded with a marked reduction in the expression levels of proteins associated with the mTOR signaling pathway. CONCLUSION Knocking down SMS attenuates the mTOR signaling pathway, thereby promoting cellular autophagy and DNA damage to enhance the radiosensitivity of CRC cells.

Establishment of cancer cell radiosensitivity database linked to multi-layer omics data.

Personalized radiotherapy based on the intrinsic sensitivity of individual tumors is anticipated, however, it has yet to be realized. To explore cancer radiosensitivity, analysis in combination with omics data is important. The Cancer Cell Line Encyclopedia (CCLE) provides multi-layer omics data for hundreds of cancer cell lines. However, the radiosensitivity counterpart is lacking. To address this issue, we aimed to establish a database of radiosensitivity, as assessed by the gold standard clonogenic assays, for the CCLE cell lines by collecting data from the literature. A deep learning-based screen of 33,284 papers identified 926 relevant studies, from which SF2 (survival fraction after 2 Gy irradiation) data were extracted. The median SF2 (mSF2) was calculated for each cell line, generating an mSF2 database comprising 285 cell lines from 28 cancer types. The mSF2 showed a normal distribution among higher and lower cancer-type hierarchies, demonstrating a large variation across and within cancer types. In selected cell lines, mSF2 correlated significantly with the single-institution SF2 obtained using standardized experimental protocols or with integral survival, a radiosensitivity index that correlates with clonogenic survival. Notably, the mSF2 for blood cancer cell lines was significantly lower than that for solid cancer cell lines, which is in line with the empirical knowledge that blood cancers are radiosensitive. Furthermore, the CCLE-derived protein levels of NFE2L2 and SQSTM1, which are involved in antioxidant damage responses that confer radioresistance, correlated significantly with mSF2. These results suggest the robustness and potential utility of the mSF2 database, linked to multi-layer omics data, for exploring cancer radiosensitivity.

Targeting Fatty Acid Synthase to Halt Tumor Progression and Enhance Radiosensitivity in Breast Cancer Cells

PurposeBreast cancer, the most prevalent cancer among women, is closely linked to abnormal glucose and lipid metabolism, leading to radioresistance by upregulating survival-signaling pathways. Overexpression of fatty acid synthase (FASN), a key enzyme in lipogenesis, results in excessive lipid synthesis in breast cancer. This study evaluated whether FASN inhibition enhanced the radiosensitivity of breast cancer cells and inhibited their progression, potentially uncovering mechanisms for new therapeutic strategies.MethodsMCF-7 breast cancer cells were treated with the FASN inhibitors orlistat and TVB-3166, and cytotoxicity was assessed using the MTT assay. Protein expression changes, migratory ability, and responses to radiotherapy were analyzed by the Western blotting, Transwell, and MTT assays, respectively. To confirm FASN dependence, MCF-7 cells were infected with shFASN lentivirus to verify the specificity of the observed effects to FASN inhibition.ResultsBoth orlistat and TVB-3166 treatments induced significant cell death. Reduced FASN, HKII, pERK, and pAKT expression levels, along with an increased BAX/p-BCL2 ratio, indicate that FASN inhibition disrupted cell proliferation and promoted apoptosis by altering tumor metabolism. Furthermore, decreased MMP9 expression correlated with reduced cell migration after FASN inhibition. Importantly, FASN inhibition significantly and dose-dependently enhanced the radiosensitivity of MCF-7 cells. These findings were validated using shFASN lentivirus, confirming that the observed effects were FASN-dependent.ConclusionFASN inhibition limited survival and migration and enhanced radiosensitivity in MCF-7 cells. These findings indicate the potential efficacy of FASN inhibitors as standalone therapies or as adjuncts to radiotherapy for breast cancer.

CD40 ligation-induced ERK activation leads to enhanced radiosensitivity in cervical carcinoma cells via promoting autophagy.

CD40, a member of the tumor necrosis factor (TNF) receptor superfamily, plays an important role not only in the immune system but also in tumor progression. CD40 ligation reportedly promotes autophagy in immune cells. However, the effects of CD40 ligation on autophagy and its mechanism in solid tumor cells are still unclear. In this study, we find that CD40 ligation promotes autophagosome formation and consequently promotes autophagic flux in cervical cancer cells. Mechanistically, this effect relies on ERK contributing to CD40 ligation-induced ATG13 upregulation by p53. Furthermore, we demonstrate that CD40 ligation-induced autophagy increases the radiosensitivity of cervical cancer cells. Taken together, our results provide new evidence for the involvement of the CD40 pathway in autophagy and radiotherapy in cervical cancer cells.

Retraction notice to "Sanyang Xuedai enhances the radiosensitivity of human non-small cell lung cancer cells via increasing iNOS/NO production" [Biomed. Pharmacother. 102 (2018) 618-625

Retraction notice to "Sanyang Xuedai enhances the radiosensitivity of human non-small cell lung cancer cells via increasing iNOS/NO production" [Biomed. Pharmacother. 102 (2018) 618-625

Loss of MK2 Enhances Radiation-Mediated Apoptosis in Bladder Cancer.

Bladder cancer patients unable to receive cystectomy or who choose to pursue organ-sparing approach are managed with definitive (chemo)radiotherapy. However, this standard of care has not evolved in decades and disease recurrence and survival outcomes remain poor. Identifying novel therapies to combine with radiotherapy (RT) is therefore paramount to improve overall patient outcomes and survival. One approach is to find cellular mechanisms that can be targeted to increase the radiosensitivity of bladder cancer. The stress-activated kinase directly downstream from p38 mitogen-activated protein kinase (MAPK), mitogen-activated protein kinase activated protein kinase 2 (MAPKAPK2 or MK2), has been shown to enhance cancer-mediated inflammation, mesenchymal gene expression, and in vivo tumor growth. Here we examined the impact that MK2 knockdown (KD) has on bladder cancer cell radiosensitivity. We utilized short hairpin RNA (shRNA) KD of MK2 using lentiviral transfection in the bladder cancer cell lines, T24 and HTB9. We compared the growth of KD cells to wild type using colony formation assays, proliferation assays and cell counts to determine differences in cell growth. Apoptosis was examined by annexin-based flow cytometry and western blots. Flow cytometry was also used for cell cycle analysis. KD clones showed a greater than 90% inhibition of MK2 expression as determined by western blot. Clonogenic assays exhibited an increase in radiosensitivity among the MK2 KD bladder cancer cells. These data were supported with proliferation assays that displayed a greater reduction in cell number following RT in MK2 KD bladder cancer cells. Annexin V binding in bladder cancer cells suggested increased apoptosis in MK2 KD cells. This was confirmed by comparing the amount of cleaved caspase products for the caspases 3 and 8 to scrambled control (SCR), and the release of cytochrome C into the cytosol. Both cell types showed disruptions in the cell cycle but at different points in the cycle. These results show that MK2 controls irradiation-induced apoptosis in bladder cancer cells.

The potential of HSA-stabilized zinc oxide nanoparticles as radiosensitizers to enhance the cytotoxic effects and radiosensitivity of cervical cancer cells

BackgroundCervical cancer is a significant cause of death among women worldwide, and limited treatment approaches are available for patients with metastatic or recurrent disease. Recently, the combination of nanoparticles (NPs) and radiotherapy (RT) has been shown to be an effective treatment because it enhances the sensitivity of cancer cells to radiation. ZnO NPs stabilized with HSA have become one of the most popular types of metal oxide nanoparticles because of their cost-effectiveness and minimal toxicity. Therefore, our study aimed to investigate the radiosensitization effects of HSA/ZnO-NPs on cervical (HeLa) cancer cells under megavoltage (MV) X-ray irradiation.MethodsHSA/ZnO-NPs were prepared and characterized by SEM and Dynamic Light Scattering (DLS) technique. The cytotoxicity of HSA/ZnO NPs was evaluated in HeLa cells via an MTT assay. The radiosensitization effects were investigated under megavoltage X-ray irradiation using a clonogenic survival assay and quantifying γH2AX foci. Moreover, apoptosis and cell cycle analyses were conducted using a Muse™ Cell Analyzer.ResultsHSA/ZnO-NPs reduced the viability of HeLa cells in a dose-dependent manner, which revealed that the IC50 of HSA/ZnO-NPs was approximately 30 µg/mL. The prepared particles exhibited moderate aggregation regarding hydrodynamic size (approximately 300–400 nm) and a negative zeta potential charge. Compared to the control group, combining HSA/ZnO-NPs with irradiation reduced the colony-forming ability and survival of HeLa cells by approximately 51% and 71% for 2 and 4 Gy, respectively. Correspondingly, the results of the apoptosis analysis showed that combining HSA/ZnO-NPs with irradiation significantly increased apoptosis induction by approximately 39.15% and 77.67% for 2 and 4 Gy, respectively. In addition, we observed a significant increase in cell cycle arrest at the S phase, by about 11.3% and 19.3% for 2 and 4 Gy, respectively.ConclusionsHSA/ZnO-NPs could significantly enhance the cytotoxic effects of ionizing radiation, which suggests the promising potential of cervical cancer radiotherapy under megavoltage X-ray irradiation.

Non-coding RNAs modulation in breast cancer radioresponse: mechanisms and therapeutic implications.

Breast cancer is the most frequent type of cancer in women, with significant incidence and fatality rates. Radiation therapy is an important therapeutic option for breast cancer patients. However, tumor cells' resistance to radiation can limit therapy efficacy, resulting in recurrence and death. Non-coding RNAs (ncRNAs) are aclass of small RNA molecules that do not translate into proteins but can affect the translation of target mRNA. Several investigations on breast cancer have demonstrated abnormal expression of ncRNAs in response to radiation. Non-coding RNAs are essential in controlling numerous processes such as DNA damage response, cancer stem cell pathways, cell cycle regulation, cell death, and inflammation. Dysregulation of ncRNAs after irradiation influences radiosensitivity or radioresistance of breast cancer cells. Understanding the molecular mechanisms underlying Radiation response can lead to innovative treatment ways to reduce breast cancer radioresistance and increase radiotherapy's efficacy. This review summarizes current research on ncRNA dysregulation following irradiation and analyzes ncRNAs' function and mechanism in modifying breast cancer cell radiosensitivity and radioresistance.

Experimental study of early evaluation of radiosensitivity in mouse models of lung cancers using 89Zr-anti-γH2AX-TAT PET imaging

BackgroundEarly evaluation of radiation sensitivity in lung cancer patients can facilitate the transition to personalized treatment strategies. To this end, we assessed the capability of 89Zr-anti-γH2AX-TAT microPET imaging in determining the radiosensitivity of lung cancer xenograft models. We prepared and conducted quality control on 89Zr-anti-γH2AX-TAT. The radiosensitivity of human non-small cell lung cancer cells (H460) and adenocarcinoma cells (A549) was analyzed through clonogenic survival experiments. Additionally, the role of γH2AX as a biomarker for radiosensitivity was validated by quantifying γH2AX foci via fluorescence staining. Subsequently, the H460 and A549 xenograft mouse models were subjected to irradiation, followed by 89Zr-anti-γH2AX-TAT microPET imaging. Concurrently, we performed immunofluorescence staining for γH2AX in tumor tissues to establish a correlation between the uptake of 89Zr-anti-γH2AX-TAT and γH2AX expression.ResultsThe surviving fraction 2 Gy (SF2) values of H460 and A549 indicating that A549 adenocarcinoma has higher radiosensitivity. The cell immunofluorescence experiment showed that the repair of γH2AX foci in H460 cells after irradiation was significantly higher than that in A549 cells, which also confirmed that A549 has higher radiosensitivity. The microPET imaging results showed the uptake of 89Zr-anti-γH2AX-TAT in the tumor of the A549 models after radiotherapy was higher than H460 models. The immunofluorescence staining of tumor tissue confirmed that the expression level of γH2AX was higher and the correlation with microPET imaging uptake was good.Conclusion89Zr-anti-γH2AX-TAT allows PET imaging of radiosensitivity in lung cancer xenograft models, and is expected to become an early evaluation method for lung cancer radiosensitivity.

Zinc Influences the Efficacy of Betulinic Acid Treatment and Radiotherapy in Breast Cancer Cells.

The trace element zinc influences a number of biological reactions, including cell growth, apoptosis, and DNA damage, which affect tumor therapy. The natural compound betulinic acid (BA) and its derivatives are known for their antiviral, antibacterial, and antitumor effects. Previous studies show that BA and 3-acetyl-28-sulfamoyloxybetulin (CAI3) have high cytotoxicity and induce radiosensitization in breast cancer cells. This study investigates the effects of zinc supplementation on treatment with BA or CAI3 and radiotherapy of breast cancer cell lines MDA-MB-231 and HS578T. Expression analysis shows that BA and CAI3 lead to altered expression of genes involved in zinc metabolism. Zinc supplementation affects cell survival and cell death alone and in combination with BA or CAI3 in both breast cancer cell lines. In MDA-MB-231 cells, zinc excess protects against ROS formation by BA or CAI3 and exhibits radioprotective effects compared to the single agent treatment. In contrast, in HS578T cells, zinc induces ROS formation but does not affect radiosensitivity. The variable effects of zinc on radiosensitivity highlight the importance of individualized treatment approaches. Although zinc has cytotoxic, pro-apoptotic, and anti-clonogenic effects, it seems worthwhile to consider its radioprotective properties when making treatment decisions in the case of adjuvant radiotherapy of breast cancer.

Aldo-keto reductase family 1 member C3 mediates radioresistance of esophageal cancer cells through suppressing MAPK and AKT signaling

BackgroundAldo-keto reductase family 1 member C3 (AKR1C3) is a radioresistance gene in esophageal cancer. This study aimed to investigate the signaling pathways that mediate the regulatory role of AKR1C3 in the radioresistance of esophageal cancer cells.MethodsThe protein levels of AKR1C3 in cancer tissue samples were compared between patients with radiosensitive and radioresistant esophageal cancer using immunohistochemical staining. AKR1C3-silenced stable KYSE170R esophageal cancer cells (KY170R-shAKR1C3) were established. Colony formation assay was employed to evaluate the radiosensitivity of cancer cells, while flow cytometry analysis was utilized to quantify reactive oxygen species (ROS) production in these cells. Additionally, Western blotting was conducted to determine protein expression levels.ResultsAKR1C3 protein exhibited significantly higher expression in radioresistant cancer tissue samples compared to radiosensitive samples. AKR1C3 silencing promoted radiosensitivity and ROS production of KYSE170R cells. At 32 h after X-ray radiation, the levels of total and phosphorylated ERK1/2, JNK, and AKT proteins were significantly elevated in KYSE170R-shAKR1C3 cells compared to untransfected KYSE170R cells. The inhibitor of AKR1C3 remarkably enhanced the radiosensitivity of KYSE170R cells. Conversely, treatment with either a MEK inhibitor or an AKT inhibitor significantly increased the radioresistance of KYSE170R-shAKR1C3 cells.ConclusionsOur results suggest that AKR1C3 mediates radioresistance of KYSE170R cells possibly through MAPK and AKT signaling.

Significant Impact of let-7d MicroRNA on Breast Cancer Cell Lines Post-Radiation Treatment

Introduction: Radiotherapy is a common treatment for breast cancer treatment, that induces DNA damage. These DNA damages are addressed through various repair pathways, which regulate the DNA repair systems and confer radio-resistance. Non-coding RNAs are a big proportion of genome transcripts without the potential to encode proteins. Related studies demonstrated that radiation affects the expression of non-coding RNAs. Let-7d, a tumor suppressor in numerous cancers, has some target genes that play a role in the DNA repair system. Materials and Methods: Human breast cancer cell lines MDA-MB-231 and MCF-7 were cultured in a Dulbecco's Modified Eagle Medium. The exponentially growing cells were treated with some doses of X-rays. After radiation treatment and cell harvesting, RNA was extracted, and cDNA synthesis was done. The let-7d miRNA expression changes were calculated with real-time quantitative reverse transcription polymerase chain reaction. Results: The results implied that radiation caused increased let-7d expression in breast cancer cell lines after radiation treatment. In addition, the results showed that 24 h after radiation, the expression of let-7d in the radioresistant cell line was higher than the radiosensitive one; 48 h after radiation, the expression of let-7d in the radiosensitive cell line was higher than the other one. Conclusions: The results demonstrated that radiation treatment increased let-7d miRNA expression in both radiosensitive and radio-resistant breast cancer cell lines. Therefore, let-7d might be involved in the radiosensitivity of breast cancer.

Discovery of Novel PROTAC SIRT6 Degraders with Potent Efficacy against Hepatocellular Carcinoma.

Sirtuin 6 (SIRT6), a member of the SIRT family, plays essential roles in the regulation of metabolism, inflammation, aging, DNA repair, and cancer development, making it a promising anticancer drug target. Herein, we present our use of proteolysis-targeting chimera (PROTAC) technology to formulate a series of highly potent and selective SIRT6 degraders. One of the degraders, SZU-B6, induced the near-complete degradation of SIRT6 in both SK-HEP-1 and Huh-7 cell lines and more potently inhibited hepatocellular carcinoma (HCC) cell proliferation than the parental inhibitors. In preliminary mechanistic studies, SZU-B6 hampered DNA damage repair, promoting the cellular radiosensitization of cancer cells. Our SIRT6 degrader SZU-B6 displayed promising antitumor activity, particularly when combined with the well-known kinase inhibitor sorafenib or irradiation in an SK-HEP-1 xenograft mouse model. Our results suggest that these PROTACs might constitute a potent therapeutic strategy for HCC.

Metformin-loaded chitosan nanoparticles augment silver nanoparticle-induced radiosensitization in breast cancer cells during radiation therapy

Recent research has focused on enhancing tumor response to radiation therapy using radiosensitizers to increase radiation absorption by cancerous tissues. This study utilized silver nanoparticles (AgNPs) as radiation sensitizers and chitosan as a nanocarrier to deliver metformin to breast cancer cells. Metformin-loaded chitosan nanoparticles (Met NPs) and AgNPs were synthesized and characterized. MCF-7 breast cancer cells were pretreated with Met NPs, followed by treatment with AgNPs and irradiation with X-rays at 2, 4, and 8 Gy doses. Cellular cytotoxicity, apoptosis, DNA damage, and 3D spheroid formation were evaluated. The synthesized Met NPs and AgNPs had average diameters of 51.5 ± 9.4 nm and 3.02 ± 0.03 nm, respectively. Cellular cytotoxicity assessment revealed the highest cytotoxicity in MCF-7 cells pretreated with Met NPs, treated with AgNPs, and irradiated with 8 Gy. Flow cytometry analysis demonstrated a 67.58 % apoptosis rate in cells pretreated with Met NPs, compared to 30.42 % in cells pretreated with plain metformin. DAPI staining revealed a 1.8-fold increase in DNA damage in cells pretreated with Met NPs and Ag NPs upon exposure to radiation. The 3D spheroid culture model confirmed a 60 % enhancement in the radiosensitivity of breast cancer cells in the presence of Met NPs and Ag NPs. The combination of Met NPs and Ag NPs represents a promising strategy to improve the therapeutic efficacy of radiation therapy for breast cancer treatment. The delivery of metformin can potentiate the radiosensitizing effects of Ag NPs, offering a novel approach to enhance cancer cells' response to radiation.

MitoTam induces ferroptosis and increases radiosensitivity in head and neck cancer cells

Background and purposeRadiotherapy (RT) is an integral treatment part for patients with head and neck squamous cell carcinoma (HNSCC), but radioresistance remains a major issue. Here, we use MitoTam, a mitochondrially targeted analogue of tamoxifen, which we aim to stimulate ferroptotic cell death with, and sensitize radioresistant cells to RT. Materials and methodsWe assessed viability, reactive oxygen species (ROS) production, disruption of mitochondrial membrane potential, and lipid peroxidation in radiosensitive (UT-SCC-40) and radioresistant (UT-SCC-5) HNSCC cells following MitoTam treatment. To assess ferroptosis specificity, we used the ferroptosis inhibitor ferrostatin-1 (fer-1). Also, total antioxidant capacity and sensitivity to tert-butyl hydroperoxide were evaluated to assess ROS-responses. 53BP1 staining was used to assess radiosensitivity after MitoTam treatment. ResultsOur data revealed increased ROS, cell death, disruption of mitochondrial membrane potential, and lipid peroxidation following MitoTam treatment in both cell lines. Adverse effects of MitoTam on cell death, membrane potential and lipid peroxidation were prevented by fer-1, indicating induction of ferroptosis. Radioresistant HNSCC cells were less sensitive to the effects of MitoTam due to intrinsic higher antioxidant capacity. MitoTam treatment prior to RT led to superadditive residual DNA damage expressed by 53BP1 foci compared to RT or MitoTam alone. ConclusionMitoTam induced ferroptosis in HNSCC cells, which could be used to overcome the elevated antioxidant capacity of radioresistant cells and sensitize such cells to RT. Treatment with MitoTam followed by RT could therefore present a promising effective therapy of radioresistant cancers.Statement of significance.Radiotherapy is applied in the treatment of a majority of cancer patients. Radioresistance due to elevated antioxidant levels can be overcome by promoting ferroptotic cell death combining ROS-inducing drug MitoTam with radiotherapy.

Restoration of Radiosensitivity by Soya Isoflavone Genistein is Accomplished by Facilitating DNA Damage Response in Radioresistant Cervical Cancer in vitro

ABSTRACT Context: Enhancing radiotherapeutic efficacy in tumor cells and sparing the normal tissues are major clinical concerns for the betterment of cancer therapy. Genistein (GEN) being a radiosensitizer ameliorates the effectiveness of radiation-induced cell killing by inducing DNA damage. This molecule is accountable for minimizing radiation-related toxicity and protecting healthy cells. However, the explicit mechanism of action of such molecules needs exploration. Aims: The objective of this study is to investigate the mechanistic action of GEN in cervical cancer cell radiosensitization. Settings and Design: Cervical squamous carcinoma cell SiHa and a radioresistant subline SiHa/RR (developed and isolated from SiHa) were taken for this study. The experiments were performed by pretreating the cells with IC30 dose of GEN, followed by acute irradiation to detect the impact of GEN in imparting radiosensitivity. Subjects and Methods: Optimal dose selection of GEN was performed by MTT assay, and radiosensitizing potency was determined by pretreating the cells with IC30 dose of GEN, followed by challenging with acute incremental doses of radiation. Mechanistic parameters were checked by clonogenic assay, cell cycle analysis, DNA damage estimation, apoptosis, and wound healing-sphere-forming assay. Statistical Analysis Used: Statistical analysis was performed in GraphPad software by performing the Student’s t-test. Results: Results depicted decreased numbers of colonies, increased frequency of DNA damage and apoptotic cells, and suppressed wound healing ability along with restrained sphere-forming ability upon the intervention of cells with GEN before radiation exposure. Such observations implied that GEN pretreatment renders improved radiosensitivity in cervical cancer by increased DNA damage-mediated G2/M arrest with subsequent apoptosis. Conclusions: GEN by inducing DNA damage stimulates radiation-induced cell killing in vitro.

DOT1L-mediated RAP80 methylation promotes BRCA1 recruitment to elicit DNA repair

Breast Cancer Type 1 Susceptibility Protein (BRCA1) is a tumor-suppressor protein that regulates various cellular pathways, including those that are essential for preserving genome stability. One essential mechanism involves a BRCA1-A complex that is recruited to double-strand breaks (DSBs) by RAP80 before initiating DNA damage repair (DDR). How RAP80 itself is recruited to DNA damage sites, however, is unclear. Here, we demonstrate an intrinsic correlation between a methyltransferase DOT1L-mediated RAP80 methylation and BRCA1-A complex chromatin recruitment that occurs during cancer cell radiotherapy resistance. Mechanistically, DOT1L is quickly recruited onto chromatin and methylates RAP80 at multiple lysines in response to DNA damage. Methylated RAP80 is then indispensable for binding to ubiquitinated H2A and subsequently triggering BRCA1-A complex recruitment onto DSBs. Importantly, DOT1L-catalyzed RAP80 methylation and recruitment of BRCA1 have clinical relevance, as inhibition of DOT1L or RAP80 methylation seems to enhance the radiosensitivity of cancer cells both in vivo and in vitro. These data reveal a crucial role for DOT1L in DDR through initiating recruitment of RAP80 and BRCA1 onto chromatin and underscore a therapeutic strategy based on targeting DOT1L to overcome tumor radiotherapy resistance.

Metformin Radiosensitizing Effect on Hypoxic Oral Squamous Cell Carcinoma Cells by GAPDH and TAGLN2.

Tumor hypoxia is associated with a poorer prognosis in cancer patients and can diminish the efficacy of radiation therapy (RT). This study investigates the potential of metformin to enhance radiosensitivity in hypoxic cancer cells. Preliminary experiments were conducted to validate the impact of hypoxia on radiation response. Reactive oxygen species (ROS) levels, cell migration, and cell death were assessed in hypoxic, radiated cells treated with metformin. Proteomic and ontological analyses were employed to identify molecular targets associated with the radiosensitizing effect of metformin. Proteomic and ontological findings were validated through patient samples and in vitro studies. Metformin amplified cell death, induced DNA fragmentation, decreased cell migration, and elevated ROS levels in hypoxic, radiated cells. Proteomic analyses revealed that GAPDH and TAGLN2 were identified as pivotal targets linked to the radiosensitizing effect of metformin. Oral cancer patients exhibited elevated levels of TAGLN2 and reduced levels of GAPDH. Metformin downregulated TAGLN2 and upregulated GAPDH in hypoxic, radiated cells. Additionally, metformin reduced levels of mutated p53. This study suggests that metformin can enhance radiosensitivity in hypoxic cells, operating through modulation of GAPDH and TAGLN2. Furthermore, metformin effectively reduces mutated p53 levels in radiated cells under hypoxic conditions.

Radiosensitizing effects of CDK4/6 inhibitors in hormone receptor-positive and HER2-negative breast cancer mediated downregulation of DNA repair mechanism and NF-κB-signaling pathway

CDK4/6 inhibitors combined with endocrine therapy prolonged survival in hormone receptor (HR)-positive and HER2-negative advanced breast cancer. We investigated whether CDK4/6 inhibitors enhance radiosensitivity and their underlying mechanisms of this subtype of breast cancer. In vitro and in vivo experiments were conducted using two HR-positive and HER2-negative breast cancer cell lines (MCF-7 and T-47D), CDK4/6 inhibitors (ribociclib and palbociclib) and radiotherapy (RT) to assess the biological functions and mechanisms. The radiation-enhancing effect was assessed using clonogenic assays; γH2AX and 53BP1 levels were assessed by immunofluorescence to evaluate DNA damage. The levels of phospho (p)-ERK, c-Myc, and DNA-double strand break (DSB)-related molecules, p-DNA-PKcs, Rad51, and p-ATM, were assessed by western blotting. We used an NF-κB p65 transcription factor assay kit to evaluate NF-κB activity. We evaluated the antitumor effect of the combination of RT and ribociclib through the MCF-7 orthotopic xenograft model. The synergistic effects of combining RT with ribociclib and palbociclib pretreatment were demonstrated by clonogenic assay. CDK4/6 inhibitors synergistically increased the numbers of RT-induced γH2AX and 53BP1, downregulated the expression of p-DNA-PKcs, Rad51 and p-ATM activated by RT, and reduced RT-triggering p-ERK expression, NF-κB activation, and its down-streaming gene, c-Myc. Combined ribociclib and RT reduced the growth of MCF-7 cell xenograft tumors, and downregulated the immunohistochemical expression of p-ERK, p-NF-κB p65, and c-Myc compared to that in the control group. Combining CDK4/6 inhibitors enhanced radiosensitivity of HR-positive and HER2-negative breast cancer cells at least by reducing DNA-DSB repair and weakening the activation of ERK and NF-κB signaling by RT.