Therapy-induced senescent tumor cell-derived extracellular vesicles promote colorectal cancer progression through SERPINE1-mediated NF-κB p65 nuclear translocation.

BACKGROUND: Cellular senescence frequently occurs during anti-cancer treatment, and persistent senescent tumor cells (STCs) unfavorably promote tumor progression through paracrine secretion of the senescence-associated secretory phenotype (SASP). Extracellular vesicles (EVs) have recently emerged as a novel component of the SASP and primarily mediate the tumor-promoting effect of the SASP. Of note, the potential effect of EVs released from STCs on tumor progression remains largely unknown. METHODS: We collected tumor tissues from two cohorts of colorectal cancer (CRC) patients to examine the expression of p16, p21, and SERPINE1 before and after anti-cancer treatment. Cohort 1 included 22 patients with locally advanced rectal cancer (LARC) who received neoadjuvant therapy before surgical resection. Cohort 2 included 30 patients with metastatic CRC (mCRC) who received first-line irinotecan-contained treatment. CCK-8, transwell, wound-healing assay, and tumor xenograft experiments were carried out to determine the impacts of EVs released from STCs on CRC progression in vitro and in vivo. Quantitative proteomic analysis was applied to identify protein cargo inside EVs secreted from STCs. Immunoprecipitation and mass spectrometer identification were utilized to explore the binding partners of SERPINE1. The interaction of SERPINE1 with p65 was verified by co-immunoprecipitation, and their co-localization was confirmed by immunofluorescence. RESULTS: Chemotherapeutic agents and irradiation could potently induce senescence in CRC cells in vitro and in human CRC tissues. The more significant elevation of p16 and p21 expression in patients after anti-cancer treatment displayed shorter disease-free survival (DFS) for LARC or progression-free survival (PFS) for mCRC. We observed that compared to non-STCs, STCs released an increased number of EVs enriched in SERPINE1, which further promoted the progression of recipient cancer cells. Targeting SERPINE1 with a specific inhibitor, tiplaxtinin, markedly attenuated the tumor-promoting effect of STCs-derived EVs. Additionally, the patients with greater increment of SERPINE1 expression after anti-cancer treatment had shorter DFS for LARC or PFS for mCRC. Mechanistically, SERPINE1 bound to p65, promoting its nuclear translocation and subsequently activating the NF-κB signaling pathway. CONCLUSIONS: We provide the in vivo evidence of the clinical prognostic implications of therapy-induced senescence. Our results revealed that STCs were responsible for CRC progression by producing large amounts of EVs enriched in SERPINE1. These findings further confirm the crucial role of therapy-induced senescence in tumor progression and offer a potential therapeutic strategy for CRC treatment.

An association analysis between mitochondrial DNA content, G10398A polymorphism, HPV infection, and the prognosis of cervical cancer in the Chinese Han population.

The aim was to analyze quantitative (mitochondrial DNA (mtDNA) content) and qualitative (G10398A polymorphism) mtDNA alterations as well as human papillomavirus (HPV) infection in cervical cancer prognosis. One hundred and twenty-two cases of formalin-fixed paraffin-embedded cervical carcinoma specimens were collected from the Yichang Tumor Hospital and Zhongnan Hospital of Wuhan University in the recent 10 years together with medical records. A quantitative real-time PCR (RT-PCR) was used to determine the copy number of the mitochondrial DNA and HPV expression levels. G10398A polymorphism was determined by PCR-RFLP assay. The overall survival of patients with higher mtDNA content was significantly reduced compared with lower mtDNA content patients (P = 0.029). But there was no difference of prognosis between the mtDNA 10398 A allele and G allele. However, the Kaplan-Meier survival curve illustrated a significantly reduced overall survival in the patients with 10398A plus high mtDNA copy number compared with the other groups (P < 0.05). Although no association between HPV expression level and cervical cancer prognosis was observed, 10398A got increased mtDNA content compared with 10398G (P < 0.05) and 10398G displayed an increased HPV-positive rate compared with 10398A. Furthermore, HPV-18 and mtDNA content were positively related in the younger subgroup (≤45 years) (correlation coefficient = 0.456, P = 0.022). This study indicated that mtDNA content and HPV infection status are associated with cervical cancer prognosis. High mitochondrial DNA content plus 10398 A may be a marker of poor prognosis in cervical cancer. And mtDNA variation may potentially influence the predisposition to HPV infection and cervical carcinogenesis.

Peripheral blood mitochondrial DNA content, A10398G polymorphism, and risk of breast cancer in a Han Chinese population.

It has been reported that quantitative alterations and sequence variations of mtDNA are associated with the onset and progression of particular types of tumor. However, the relationship between mtDNA content, certain mtDNA polymorphisms in peripheral blood leukocytes and breast cancer risk remain obscure. This study was undertaken to investigate whether mtDNA content and the A10398G polymorphism in peripheral blood leukocytes could be used as risk predictors for breast cancer in Han Chinese women. Blood samples were obtained from a total of 506 breast cancer patients and 520 matched healthy controls. The mtDNA content was measured by using quantitative real-time PCR assay; A10398G polymorphism was determined by PCR-RFLP assay. There was no statistically significant difference between cases and controls in terms of peripheral blood mtDNA content or A10398G polymorphism. However, further analysis suggested that the risk of breast cancer was associated with decreased mtDNA content in premenopausal women (P = 0.001; odds ratio = 0.54; 95% confidence interval, 0.38-0.77), with increased mtDNA content in postmenopausal women (P = 0.027; odds ratio = 1.49; 95% confidence interval, 1.05-2.11). In addition, the associations between mtDNA content and several clinicopathological parameters of cases such as age, menopausal status, and number of pregnancies and live births were observed. This case-control study indicated that the peripheral blood mtDNA content might be a potential biomarker to evaluate the risk of breast cancer for selected Chinese women.

PD-1/CD80+ small extracellular vesicles from immunocytes induce cold tumours featured with enhanced adaptive immunosuppression.

Only a minority of cancer patients benefit from immune checkpoint blockade therapy. Sophisticated cross-talk among different immune checkpoint pathways as well as interaction pattern of immune checkpoint molecules carried on circulating small extracellular vesicles (sEV) might contribute to the low response rate. Here we demonstrate that PD-1 and CD80 carried on immunocyte-derived sEVs (I-sEV) induce an adaptive redistribution of PD-L1 in tumour cells. The resulting decreased cell membrane PD-L1 expression and increased sEV PD-L1 secretion into the circulation contribute to systemic immunosuppression. PD-1/CD80+ I-sEVs also induce downregulation of adhesion- and antigen presentation-related molecules on tumour cells and impaired immune cell infiltration, thereby converting tumours to an immunologically cold phenotype. Moreover, synchronous analysis of multiple checkpoint molecules, including PD-1, CD80 and PD-L1, on circulating sEVs distinguishes clinical responders from those patients who poorly respond to anti-PD-1 treatment. Altogether, our study shows that sEVs carry multiple inhibitory immune checkpoints proteins, which form a potentially targetable adaptive loop to suppress antitumour immunity.

A tumor cell exosome-mimicking multifunctional nanozyme for targeted breast cancer radiotherapy.

Radiotherapy (RT) has been extensively used for the treatment of breast cancer. However, the efficacy of RT is reduced by the high content of reducing species within cells (such as glutathione (GSH)). In addition, high-dose radiotherapy is often accompanied by serious side effects. In an attempt to resolve these issues, a tumor cell exosome-mimicking multifunctional nanozyme system (CuPy-Au@EM) was developed as a radiosensitizer, which consists of an internal AuNP-embedded CuPy nanozyme core and an external tumor cell exosome membrane. The exosome membrane protein on the surface of CuPy-Au@EM leads to the accurate localization of nano-materials in the tumor site; simultaneously, the level of H2O2 will be enhanced because of the GOx-like activity of AuNPs. Then CuPy-Au@EM would continue to trigger a rapid decline in cellular GSH content and the production of a large number of hydroxyl radicals (˙OH) through its glutathione peroxidase (GPx) and peroxidase (POD) activities allows for the extension of the radiotherapeutic cascade. Studies conducted in vivo and in vitro demonstrated that the combination of CuPy-Au@EM and moderate dose RT (4 Gy) can significantly reduce tumor proliferation. These findings indicated that CuPy-Au@EM nanospheres could be plausibly developed into promising radio-sensitizers on tumors.

HRS Regulates Small Extracellular Vesicle PD-L1 Secretion and Is Associated with Anti-PD-1 Treatment Efficacy.

PD-L1 localized to immunosuppressive small extracellular vesicles (sEV PD-L1) contributes to tumor progression and is associated with resistance to immune-checkpoint blockade (ICB) therapy. Here, by establishing a screening strategy with a combination of tissue microarray (TMA), IHC staining, and measurement of circulating sEV PD-L1, we found that the endosomal sorting complex required for transport (ESCRT) member protein hepatocyte growth factor-regulated tyrosine kinase substrate (HRS) was the key regulator of circulating sEV PD-L1 in head and neck squamous cell carcinoma (HNSCC) patients. Increased HRS expression was found in tumor tissues and positively correlated with elevated circulating sEV PD-L1 in patients with HNSCC. The expression of HRS was also negatively correlated to the infiltration of CD8+ T cells. Knockdown of HRS markedly reduced PD-L1 expression in HNSCC cell-derived sEVs, and these sEVs from HRS knockdown cells showed decreased immunosuppressive effects on CD8+ T cells. Knockout of HRS inhibited tumor growth in immunocompetent mice together with PD-1 blockade. Moreover, a higher HRS expression was associated with a lower response rate to anti-PD-1 therapy in patients with HNSCC. In summary, our study reveals HRS, the core component of ESCRT-0, regulates sEV PD-L1 secretion, and is associated with the response to ICB therapy in patients with HNSCC, suggesting HRS is a promising target to improve cancer immunotherapy.

Impact of Adjuvant Chemoradiotherapy on Survival of Resected Pancreatic Adenocarcinoma Cancer: A Surveillance, Epidemiology and End Results (SEER) Analysis.

BACKGROUND: The benefits of postoperative adjuvant chemoradiotherapy (CRT) for pancreatic cancer remain controversial. The purpose of this study is to determine if adjuvant CRT can improve the overall survival of postoperative pancreatic cancer patients compared to adjuvant chemotherapy (CT). METHODS: Patients with resected pancreas adenocarcinoma were identified in the Surveillance, Epidemiology, and End Results (SEER) database (2004-2016). Multivariate Cox regression was used to determine the factors related to survival rate. Selection bias was reduced to a minimum through propensity matching analysis. Subgroup analyses by clinical characteristics were performed. RESULTS: This study identified 10,097 patients who received adjuvant CT (n = 5,454) or adjuvant CRT (n = 4,643). On multivariate analysis, age, sex, tumor size, site, grade, stage, T stage, and lymph node metastasis were independent risk factors for OS. The basic clinical characteristics were well balanced after propensity matching. After propensity matching, CRT can improve the survival rate compared with CT [median OS: 22 months vs 23 months (HR, 0.928; 95% CI, 0.881-0.977; P = 0.004)]. Subgroup analysis indicated that the survival benefit of adjuvant chemoradiotherapy was more significant in patients with female (HR, 0.860; 95% CI, 0.798-0.926; P = 0.005 for interaction) or T3 (HR, 0.905; 95% CI, 0.855-0.957; P = 0.04 for interaction) or lymph nodes positive (HR, 0.883; 95% CI, 0.832-0.938; P = 0.005 for interaction). CONCLUSION: Adjuvant CRT was associated with improved survival compared with adjuvant CT in patients with resection of pancreatic ductal adenocarcinoma. The benefit was more significant in patients with female or T3 or lymph nodes positive.

Mitochondrial dysfunction induces radioresistance in colorectal cancer by activating [Ca2+]m-PDP1-PDH-histone acetylation retrograde signaling.

Mitochondrial retrograde signaling (mito-RTG) triggered by mitochondrial dysfunction plays a potential role in regulating tumor metabolic reprogramming and cellular sensitivity to radiation. Our previous studies showed phos-pyruvate dehydrogenase (p-PDH) and PDK1, which involved in aerobic glycolysis, were positively correlated with radioresistance, but how they initiate and work in the mito-RTG pathway is still unknown. Our further genomics analysis revealed that complex I components were widely downregulated in mitochondrial dysfunction model. In the present study, high expression of p-PDH was found in the complex I deficient cells and induced radioresistance. Mechanistically, complex I defects led to a decreased PDH both in cytoplasm and nucleus through [Ca2+]m-PDP1-PDH axis, and decreased PDH in nucleus promote DNA damage repair (DDR) response via reducing histone acetylation. Meanwhile, NDUFS1 (an important component of the complex I) overexpression could enhance the complex I activity, reverse glycolysis and resensitize cancer cells to radiation in vivo and in vitro. Furthermore, low NDUFS1 and PDH expression were validated to be correlated with poor tumor regression grading (TRG) in local advanced colorectal cancer (CRC) patients underwent neoadjuvant radiotherapy. Here, we propose that the [Ca2+]m-PDP1-PDH-histone acetylation retrograde signaling activated by mitochondrial complex I defects contribute to cancer cell radioresistance, which provides new insight in the understanding of the mito-RTG. For the first time, we reveal that NDUFS1 could be served as a promising predictor of radiosensitivity and modification of complex I function may improve clinical benefits of radiotherapy in CRC.

Pretreatment serum vitamin level predicts severity of radiation-induced oral mucositis in patients with nasopharyngeal carcinoma.

BACKGROUND: Radiation-induced mucositis (RIOM) is a common radiotherapy toxicity. We aimed to evaluate the relationship of serum vitamin status with RIOM among nasopharyngeal carcinoma (NPC) patients who underwent radiotherapy. METHODS: NPC patients who underwent concurrent chemoradiotherapy with available pretreatment serum vitamin values were included. Serum vitamin levels and clinical characteristics were collected. Logistic regression analysis and receiver operating characteristic curves were conducted to explore the potential risk factors and corresponding cut-off values for severe RIOM. RESULTS: Two hundred and forty NPC patients were enrolled. Multivariate regression analysis showed that mean oral cavity radiation dose (OR = 2.042; 95% CI = 1.585-2.630; P < .001), weekly concurrent chemotherapy (OR = 3.898; 95% CI = 1.085-14.004; P = .037), lower serum level of vitamin B2 (OR = 0.951; 95% CI = 0.924-0.978; P < .001), and vitamin C (OR = 0.455; 95% CI = 0.346-0.598; P < .001) were independent risk factors for developing severe RIOM. CONCLUSIONS: The findings of this study revealed that serum vitamin status could predict the severity of RIOM, providing a theoretical basis for the prevention and treatment of RIOM.

Impact of treatment delay due to the pandemic of COVID-19 on the efficacy of immunotherapy in head and neck cancer patients.

Immunotherapy has been a new standard for recurrent/metastatic head and neck cancers (R/M HNC). One of the prominent characteristics of cancer immunotherapy is the induction of immune memory followed by endured treatment response. However, whether and how a treatment delay would impact on the efficacy of immunotherapy has not been well determined. During the outbreak of COVID-19, a number of cancer patients in Wuhan, the epicenter of the pandemic in China, had experienced long-lasting city lockdown and delay of immunotherapies. Here, we retrospectively analyzed 24 HNC patients treated with immune checkpoint inhibitors in our cancer institute prior to the outbreak of COVID-19 who were re-evaluated after the restoration of regular medical care. Of these 24 patients, 10 patients had achieved complete response (CR) or partial response (PR), 12 patients had achieved stable disease (SD), and 2 patients had received just one cycle treatment without efficacy evaluation before treatment delay. The median delay was 3.75 months (range 1.73-8.17 months). Re-evaluation after treatment delay revealed that ten patients (10/10) who achieved CR or PR, two patients (2/2) who received just one cycle treatment without efficacy evaluation and seven patients (7/12) who achieved SD before outbreak of COVID-19 maintained tumor response after treatment delay. Among the rest five patients who had achieved SD, four patients were re-evaluated as progressive disease (PD) due to treatment delay and one patient died after treatment interruption without re-evaluation. Our results from a small cohort of R/M HNC patients showed that treatment delay of three to four months might have mild, if any, impact on the efficacy of immunotherapy for patients with controlled disease.

Fenofibrate-induced mitochondrial dysfunction and metabolic reprogramming reversal: the anti-tumor effects in gastric carcinoma cells mediated by the PPAR pathway.

Cancer cells reprogram their metabolism to adapt to fast growth and environmental demands, which differ them from normal cells. Mitochondria are central to the malignant metabolism reprogramming process. Here, we report that PPARα was highly expressed in gastric cancer tissues and negatively correlated with prognosis. Fenofibrate, a common drug used to treat severe hypertriglyceridemia and mixed dyslipidemia, reversed cellular metabolism and mitochondrial dysfunction in gastric cancer cells through PPARα. Our results show that fenofibrate altered glucose and lipid metabolism, inhibited gastric cancer cell proliferation, and promoted apoptosis in gastric cancer cells. We further show that fenofibrate induced mitochondrial reprogramming via CPT1 and the fatty acid oxidation pathway, as well as by activating the AMPK pathway and inhibiting the HK2 pathway. Additionally, fenofibrate inhibited subcutaneous gastric cancer cell tumor growth without obvious toxicity in mice. Collectively, our results indicate that fenofibrate exhibits anti-tumor activity in vitro and in vivo via the mitochondria and metabolic reprogramming, demonstrating that mitochondrial regulation and the normalization of cancer cell metabolism are novel therapeutic strategies for cancer.

Predictive value of pancreatic dose-volume metrics on sarcopenia rate in gastric cancer patients treated with adjuvant chemoradiotherapy.

OBJECTIVE: To evaluate the relationship of sarcopenia with the pancreatic dose-volume histogram (DVH) in gastric cancer patients treated with adjuvant chemoradiotherapy (CRT) after radical gastrectomy. METHODS: A retrospective study was performed on the data in Zhongnan Hospital of Wuhan University from January 2008 to December 2016. Skeletal muscle index (SMI) was analyzed by cross-sectional areas of body composition at the level of third lumbar (L3) vertebrae, which was measured using single-slice computer tomograph (CT) prior to CRT, at 6 months and 12 months after CRT respectively. Logistic regression analysis was conducted to explore the potential clinical risk factors of sarcopenia in this patients cohort. Regarding the dosimetrics of pancreas, the sarcopenia rate was compared between the two groups divided according to the cut-off value determined by the receiver operating characteristic (ROC) curves. RESULTS: One hundred and fifty-three gastric cancer patients were eligible in this study. The median postoperative follow-up was 36 (7-115) months. The mean dose of pancreas was 4399.7 ± 396.0 cGy. The incidence of sarcopenia prior to CRT, at 6 months and 12 months later were 29.4% (45/153), 27.3% (35/128) and 37.0% (37/100). Both sarcopenia at 6 months (HR = 2.038, 95%CI = 1.084-3.833, P = 0.027) and sarcopenia at 12 months (HR = 2.216, 95%CI = 1.007-4.873, P = 0.048) were the independent prognostic factor of gastric cancer patients. V46 remained to be the only independent risk factor of sarcopenia at 6 months (OR = 3.889, 95%CI = 1.099-13.764, P = 0.035) and 12 months (OR = 6.067, 95%CI = 1.687-21.821, P = 0.006) in multivariate logistic regression analysis. Among the dosimetric parameters used for ROC analysis, the V46 showed the highest area under the curve (AUC = 0.707). Here is the relationship between sarcopenia rate and the cut-off value for V46. Higher sarcopenia rate at 6 months was noted in 42.6% patients with V46 ≥ 57% compared with 9% of patients with V46 < 57% (P < 0.001). The sarcopneia rate at 12 months was 52% with V46 ≥ 57% and 25% with V46 < 57% (P = 0.010). CONCLUSION: Gastric cancer with sarcopenia after adjuvant CRT had poorer survival. Higher dose and larger irradiated volume of pancreas correlated with higher risk of sarcopenia. Appropriated administration of pancreas dose-volume may be conducive to reduce the risk of sarcopenia and improve survival in gastric cancer patients treated with adjuvant CRT.

Downregulation of Mitochondrial Single Stranded DNA Binding Protein (SSBP1) Induces Mitochondrial Dysfunction and Increases the Radiosensitivity in Non-Small Cell Lung Cancer Cells.

Radiotherapy is one of the major therapeutic strategies for human non-small cell lung cancer (NSCLC), but intrinsic radioresistance of cancer cells makes a further improvement of radiotherapy for NSCLC challenging. Mitochondrial function is frequently dysregulated in cancer cells for adaptation to the changes of tumor microenvironment after exposure to radiation. Therefore, targeting mitochondrial biogenesis and bioenergetics is an attractive strategy to sensitize cancer cells to radiation therapy. In this study, we found that downregulation of single-strand DNA-binding protein 1 (SSBP1) in H1299 cells was associated with inducing mitochondrial dysfunction and increasing radiosensitivity to ionizing radiation. Mechanistically, SSBP1 loss induced mitochondrial dysfunction via decreasing mitochondrial DNA copy number and ATP generation, enhancing the mitochondrial-derived ROS accumulation and downregulating key glycolytic enzymes expression. SSBP1 knockdown increased the radiosensitivity of H1299 cells by inducing increased apoptosis, prolonged G2/M phase arrest and defective homologous recombination repair of DNA double-strand breaks. Our findings identified SSBP1 as a radioresistance-related protein, providing potential novel mitochondrial target for sensitizing NSCLC to radiotherapy.

2-Methoxyestradiol enhances radiosensitivity in radioresistant melanoma MDA-MB-435R cells by regulating glycolysis via HIF-1α/PDK1 axis.

HIF-1α overexpression is associated with radio-resistance of various cancers. A radioresistant human melanoma cell model MDA-MB-435R (435R) was established by us previously. Compared with the parental cells MDA-MB­435 (435S), an elevated level of HIF-1α expression in 435R cells was demonstrated in our recent experiments. Therefore, in the current study, we sought to determine whether selective HIF-1α inhibitors could radiosensitize the 435R cells to X-ray, and to identify the potential mechanisms. Our data demonstrated that inhibition of HIF-1α with 2-methoxyestradiol (2-MeOE2) significantly enhanced radiosensitivity of 435R cells. 2-MeOE2 increased DNA damage and ratio of apoptosis cells induced by irradiation. Whereas, cell proliferation and the expression of pyruvate dehydrogenase kinase 1 (PDK1) were decreased after 2-MeOE2 treatment. The change of expression of GLUT1, LDHA and the cellular ATP level and extracellular lactate production indicates that 2-MeOE2 suppressed glycolytic state of 435R cells. In addition, the radioresistance, glycolytic state and cell proliferation of 435R cells were also decreased after inhibiting pyruvate dehydrogenase kinase 1 (PDK1) with dichloroacetate (DCA). DCA could also increase DNA damage and ratio of apoptotic cells induced by irradiation. These results also suggest that inhibition of HIF-1α with 2-MeOE2 sensitizes radioresistant melanoma cells 435R to X-ray irradiation through targeting the glycolysis that is regulated by PDK1. Selective inhibitors of HIF-1α and glycolysis are potential drugs to enhance radio-sensitivity of melanoma cells.

The MPO-463G>A polymorphism and lung cancer risk: a meta-analysis based on 22 case-control studies.

BACKGROUND: Myeloperoxidase (MPO) is an endogenous oxidant enzyme that produces reactive oxygen species (ROS) and may be involved in lung carcinogenesis. The MPO-463G>A polymorphism influences MPO transcription and has been associated with lung cancer susceptibility. However, the association between the MPO-463G>A polymorphism and lung cancer risk remains controversial. METHOD: To investigate the effect of this polymorphism on lung cancer susceptibility, we performed a meta-analysis based on 22 published case-control studies including 7,520 patients with lung cancer and 8,600 controls. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of the association. RESULTS: Overall, there was no evidence for significant association between MPO-463G>A polymorphism and lung cancer susceptibility (for AA versus GG: OR = 0.91, 95%CI = 0.67-1.24; for GA versus GG: OR = 0.87, 95% CI = 0.78-0.98; for AA/GA versus GG: OR = 0.90, 95% CI = 0.80-1.01; for AA versus GA/GG: OR = 0.96, 95% CI = 0.72-1.28). In the stratified analyses by ethnicity, source of controls and smoking status, we also did not find any significant association between them. CONCLUSIONS: In summary, this meta-analysis suggests MPO-463G>A polymorphism may not be a risk factor for developing lung cancer. However, further prospective well-designed population-based studies with larger sample size are expected to validate the results.

Suppression of Ku80 correlates with radiosensitivity and telomere shortening in the U2OS telomerase-negative osteosarcoma cell line.

Ku70/80 heterodimer is a central element in the nonhomologous end joining (NHEJ) DNA repair pathway, Ku80 playing a key role in regulating the multiple functions of Ku proteins. It has been found that the Ku80 protein located at telomeres is a major contributor to radiosensitivity in some telomerase positive human cancer cells. However, in ALT human osteosarcoma cells, the precise function in radiosensitivity and telomere maintenance is still unknown. The aim of this study was to investigate the effects of Ku80 depletion in the U2OS ALT cell line cell line. Suppression of Ku80 expression was performed using a vector-based shRNA and stable Ku80 knockdown in cells was verified by Western blotting. U2OS cells treated with shRNA-Ku80 showed lower radiobiological parameters (D0, Dq and SF2) in clonogenic assays. Furthermore, shRNA-Ku80 vector transfected cells displayed shortening of the telomere length and showed less expression of TRF2 protein. These results demonstrated that down-regulation of Ku80 can sensitize ALT cells U2OS to radiation, and this radiosensitization is related to telomere length shortening.

Prognostic value of mitochondrial DNA content and G10398A polymorphism in non-small cell lung cancer.

Non-small cell lung cancer (NSCLC) is one of the leading causes of cancer-related mortality worldwide. Mitochondrial dysfunction has been postulated to render cancer cells resistant to apoptosis based on the Warburg hypothesis. However, few studies have investigated the prognostic value of mitochondrial DNA (mtDNA) content and G10398A polymorphism in NSCLC patients. mtDNA copy number and G10398A polymorphism in 128 NSCLC tissue samples were assessed by real-time PCR (RT-PCR) and PCR-RFLP respectively, and their relationship to prognosis were analyzed by survival analysis and Cox proportional hazards model. In vitro, an mtDNA deletion A549 ρ(0) cell model was utilized to assess the function of mtDNA on radiosensitivity. Cell cycle distribution and reactive oxygen species (ROS) were analyzed to elucidate the potential mechanisms. For the whole group, the median follow-up time and overall survival time were 22.5 and 23.4 months, respectively. Patients with high mtDNA content had a marginally longer survival time than patients with low mtDNA content (P=0.053). Moreover, patients with high mtDNA content plus 10398G had a significantly longer overall survival time compared with those having low mtDNA content plus 10398A (47 vs. 27 months, P<0.05). In addition, multivariate analysis showed that stage and low mtDNA content plus 10398A were the two most independent prognostic factors. In vitro, the A549 ρ(0) cells showed more resistance to radiation than ρ(+) cells. Following radiation, ρ(0) cells showed delayed G2 arrest and lower ROS level as compared to ρ(+) cells. In conclusion, the present study suggests that in patients with NSCLC, low mtDNA content plus 10398A could be a marker of poor prognosis which is associated with resistance to anticancer treatment caused by low mtDNA content plus 10398A polymorphism resulting in mitochondrial dysfunction.