Proposals for the delineation of neck clinical target volume for definitive Radiation therapy in patients with oral/ oropharyngeal squamous cell cancer based on lymph node distribution.

PURPOSE/OBJECTIVE(S): To establish the distribution pattern of cervical lymph node metastasis (LNM) and propose optimized clinical target volume (CTV) boundaries specific to oral/ oropharyngeal squamous cell cancer (OSCC/OPSCC). MATERIALS/METHODS: 531 patients with pathologically confirmed OSCC/OPSCC were enrolled from January 2013 to June 2022. Patients were stratified into two groups based on the minimal distance from the lesion's edge to the body's midline: ≤1 cm or > 1 cm. The geometric center of cervical metastatic LN was marked on a template CT. LN distribution probability maps were established. The relationships between the LN distribution and consensus guidelines were analyzed to propose modifications for CTV boundaries specific to OSCC/OPSCC. RESULTS: A total of 1962 positive LNs were enrolled. Compared with the > 1 cm group, the ≤ 1 cm group has following feature tendencies: male smokers, younger, median organs, large gross lesion, infiltrative growth pattern, contralateral LNM. The most frequently involved level of LNM was ipsilateral II, but ipsilateral Ib had the highest involvement rate in the > 1 cm OSCC group. In addition, tongue cancer had a higher incidence of LN extranodal extension (ENE), which mainly distributes in ipsilateral level II. The skip metastasis was prone to from level III to Vb (3.5 %) in LN(+)/ENE (-), and level Ib to VIa (3.7 %) in LN(+)/ENE (+). Accordingly, we proposed the following modifications: 1. only including lateral and posterior margin of submandibular gland within 5 mm; 2. retracting posterior boundary of level II to front edge of levator scapula muscle, and descending the upper boundary to transverse process of C2 vertebra only for OSCC; 3. including posterior third of thyroglossal muscle or anterior edge of sternocleidomastoid muscle; 4. sparing level Va in case of only level II involvement; 5. including upper area of the thyroid cartilage plate in case of level Ib LN(+)/ENE (+); 6. sparing level VIIa is considered. CONCLUSION: This is the first description of LN topographic spread patterns for OSCC/OPSCC. Modified CTV for prophylactic irradiation was proposed to spare the organs at risk and minimize adverse effects.

Single-cell RNA sequencing reveals recruitment of the M2-like CCL8high macrophages in Lewis lung carcinoma-bearing mice following hypofractionated radiotherapy.

BACKGROUND: Tumor-associated macrophages (TAMs) play a pivotal role in reshaping the tumor microenvironment following radiotherapy. The mechanisms underlying this reprogramming process remain to be elucidated. METHODS: Subcutaneous Lewis lung carcinoma (LLC) murine model was treated with hypofrationated radiotherapy (8 Gy × 3F). Single-cell RNA sequencing was utilized to identify subclusters and functions of TAMs. Multiplex assay and enzyme-linked immunosorbent assay (ELISA) were employed to measure serum chemokine levels. Bindarit was used to inhibit CCL8, CCL7, and CCL2. The infiltration of TAMs after combination treatment with hypofractionated radiotherapy and Bindarit was quantified with flow cytometry, while the influx of CD206 and CCL8 was assessed by immunostaining. RESULTS: Transcriptome analysis identified a distinct subset of M2-like macrophages characterized by elevated Ccl8 expression level following hypofractionated radiotherapy in LLC-bearing mice. Remarkbly, hypofractionated radiotherapy not only promoted CCL8high macrophages infiltration but also reprogrammed them by upregulating immunosuppressive genes, thereby fostering an immunosuppressive tumor microenvironment. Additioinally, hypofractionated radiotherapy enhanced the CCL signaling pathway, augmenting the pro-tumorigenic functions of CCL8high macrophages and boosting TAMs recruitment. The adjunctive treatment combining hypofractionated radiotherapy with Bindarit effectively reduced M2 macrophages infiltration and prolonged the duration of local tumor control. CONCLUSIONS: Hypofractionated radiotherapy enhances the infiltration of CCL8high macrophages and amplifies their roles in macrophage recruitment through the CCL signaling pathway, leading to an immunosuppressive tumor microenvironment. These findings highlight the potential of targeting TAMs and introduces a novel combination to improve the efficacy of hypofractionated radiotherapy.

Eosinophil dynamics during chemo-radiotherapy correlate to clinical outcome in stage â ¡-â £a nasopharyngeal carcinoma patients: Results from a large cohort study.

BACKGROUND AND PURPOSE: We investigated the dynamics of eosinophil depletion during definitive concurrent chemo-radiotherapy (CCRT) and their association with the prognosis of stage Ⅱ-Ⅳa nasopharyngeal carcinoma (NPC) patients. MATERIALS AND METHODS: Fuzzy C-means algorithm (FCMA) assessed longitudinal trends in circulating eosinophil counts (CECs) of 1225 patients throughout the period of radical radiotherapy. The prognostic impact on patients' survival was evaluated with Kaplan-Meier analysis and Cox proportional risk model was used to determine the hazard ratio for adverse prognostic effects in grades of eosinophil depletion. The interactive effect of pre-treatment CECs and CCRT on outcomes was evaluated using HRs within the framework of Cox regression models. RESULTS: Three grades of eosinophil depletion, as defined by the interaction between dynamic types of CECs in the period of treatment and the value of CECs at the termination of treatment, significantly stratified the poor prognosis in terms of progression-free survival (PFS), overall survival (OS), and distant metastasis-free survival (DMFS) [1.57-fold (P = 0.001), 1.69-fold (P = 0.007), and 1.51-fold (P = 0.019) for G1, 2.4-fold (P < 0.001), 2.76-fold (P < 0.001), and 2.31-fold (P < 0.001) for G2, as compared with G0]. Furthermore, high levels of pre-treatment CECs acted as the strongest protective factor against severe depletion grade (G0 vs. G2, HR = 0.20, P = 0.005; G1 vs. G2, HR = 0.14, P < 0.001). However, compared with radiotherapy alone, the benefit from CCRT was attenuated in patients with high pre-treatment CECs. CONCLUSIONS: CECs reduction after treatment in patients with NPC may be helpful in the clinical setting to aid in assessing the prognosis for standard treatment of NPC.

Association of public health insurance with cancer-specific mortality risk among patients with nasopharyngeal carcinoma: a prospective cohort study in China.

Objective: Health insurance programs are effective in preventing financial hardship in patients with cancer. However, not much is known about how health insurance policies, especially in Southwest China with a high incidence of nasopharyngeal carcinoma (NPC), influence patients' prognosis. Here, we investigated the association of NPC-specific mortality with health insurance types and self-paying rate, and the joint effect of insurance types and self-paying rate. Materials and methods: This prospective cohort study was conducted at a regional medical center for cancer in Southwest China and included 1,635 patients with pathologically confirmed NPC from 2017 to 2019. All patients were followed up until May 31, 2022. We determine the cumulative hazard ratio of all-cause and NPC-specific mortality in the groups of various insurance kinds and the self-paying rate using Cox proportional hazard. Results: During a median follow-up period of 3.7 years, 249 deaths were recorded, of which 195 deaths were due to NPC. Higher self-paying rate were associated with a 46.6% reduced risk of NPC-specific mortality compared to patients with insufficient self-paying rate (HR: 0.534, 95% CI: 0.339-0.839, p = 0.007). For patients covered by Urban and Rural Residents Basic Medical Insurance (URRMBI), and for patients covered by Urban Employee Basic Medical Insurance, each 10% increase in the self-paying rate reduced the probability of NPC-specific death by 28.3 and 25%, respectively (UEBMI). Conclusion: Results of this study showed that, despite China's medical security administration improved health insurance coverage, NPC patients need to afford the high out-of-pocket medical costs in order to prolong their survival time.

Radiation-induced eosinophil increase ratio predicts patient outcomes in non-small celllung cancer.

Background and purpose: Radiotherapy (RT) is a double-edged sword in regulating immune responses. This study aimed to investigate the impact of thoracic RT on circulating eosinophils and its association with patient outcomes in non-small cell lung cancer (NSCLC). Materials and methods: This retrospective study included 240 patients with advanced NSCLC treated with definitive thoracic RT from January 2012 to January 2020. Statistics included Kaplan-Meier analysis of overall survival (OS) and progression-free survival (PFS), multivariate Cox analyses to identify significant variables, and Spearman's correlation to qualify the relationship between dose-volume histogram (DVH) parameters and EIR. Results: Absolute eosinophil counts (AECs) showed an increasing trend during RT and an obvious peak in the 1st month after RT. Thresholds of eosinophil increase ratio (EIR) at the 1st month after RT for both OS and PFS were 1.43. Patients with high EIR above 1.43 experienced particularly favorable clinical outcomes (five-year OS: 21% versus 10%, P<0.0001; five-year PFS: 10% versus 8%, P=0.014), but may not derive PFS benefit from the addition of chemotherapy to RT. The higher a patient's EIR, the larger the potential benefit in the absence of chemotherapy. DVH parameters including heart mean dose and heart V10 were negatively associated with EIR. None of these DVH parameters was correlated with the clinical outcomes. Conclusion: EIR may serve as a potential biomarker to predict OS and PFS in NSCLC patients treated with RT. These findings require prospective studies to evaluate the role of such prognostic marker to identify patients at risk to tailor interventions.

Protein Phosphatase 2A-Dependent Mitotic hnRNPA1 Dephosphorylation and TERRA Formation Facilitate Telomere Capping.

The heterogeneous nuclear ribonucleoprotein A1 (hnRNPA1), telomeric repeat-containing RNA (TERRA), and protection of telomeres 1 (POT1) have been reported to orchestrate to displace replication protein A (RPA) from telomeric overhangs, ensuring orderly telomere replication and capping. Our previous studies further demonstrated that DNA-dependent protein kinase catalytic subunit (DNA-PKcs)-dependent hnRNPA1 phosphorylation plays a crucial role in the promotion of hnRNPA1 binding to telomeric overhangs and RPA displacement during G2-M phases. However, it is unclear that how the subsequent exchange between hnRNPA1 and POT1 is orchestrated. Here we report that the protein phosphatase 2A (PP2A) depends on its scaffold subunit, which is called PPP2R1A, to interact with and dephosphorylate hnRNPA1 in the late M phase. Furthermore, PP2A-mediated hnRNPA1 dephosphorylation and TERRA accumulation act in concert to promote the hnRNPA1-to-POT1 switch on telomeric single-stranded DNA. Consequently, defective PPP2R1A results in ataxia telangiectasia and Rad3-related (ATR)-mediated DNA damage response at telomeres as well as induction of fragile telomeres. Combined inhibition of ATR and PP2A induces entry into a catastrophic mitosis and leads to synthetic lethality of tumor cells. In addition, PPP2R1A levels correlate with clinical stages and prognosis of multiple types of cancers. Taken together, our results indicate that PP2A is critical for telomere maintenance. IMPLICATIONS: This study demonstrates that the PP2A-dependent hnRNPA1 dephosphorylation and TERRA accumulation facilitates the formation of the protective capping structure of newly replicated telomeres, thus exerting essential oncogenic role in tumorigenesis.

Radiation-induced PD-L1 expression in tumor and its microenvironment facilitates cancer-immune escape: a narrative review.

Background and Objective: Radiotherapy (RT) is one of the fundamental anti-cancer regimens by means of inducing in situ tumor vaccination and driving a systemic anti-tumor immune response. It can affect the tumor microenvironment (TME) components consisting of blood vessels, immunocytes, fibroblasts, and extracellular matrix (ECM), and might subsequently suppress anti-tumor immunity through expression of molecules such as programmed death ligand-1 (PD-L1). Immune checkpoint inhibitors (ICIs), especially anti-programmed cell death 1 (PD-1)/PD-L1 therapies, have been regarded as effective in the reinvigoration of the immune system and another major cancer treatment. Experimentally, combination of RT and ICIs therapy shows a greater synergistic effect than either therapy alone. Methods: We performed a narrative review of the literature in the PubMed database. The research string comprised various combinations of "radiotherapy", "programmed death-ligand 1", "microenvironment", "exosome", "myeloid cell", "tumor cell", "tumor immunity". The database was searched independently by two authors. A third reviewer mediated any discordance of the results of the two screeners. Key Content and Findings: RT upregulates PD-L1 expression in tumor cells, tumor-derived exosomes (TEXs), myeloid-derived suppressor cells (MDSCs), and macrophages. The signaling pathways correlated to PD-L1 expression in tumor cells include the DNA damage signaling pathway, epidermal growth factor receptor (EGFR) pathway, interferon gamma (IFN-γ) pathway, cGAS-STING pathway, and JAK/STATs pathway. Conclusions: PD-L1 upregulation post-RT is found not only in tumor cells but also in the TME and is one of the mechanisms of tumor evasion. Therefore, further studies are necessary to fully comprehend this biological process. Meanwhile, combination of therapies has been shown to be effective, and novel approaches are to be developed as adjuvant to RT and ICIs therapy.

Reduced-dose radiation in human papillomavirus-associated oropharyngeal carcinoma can improve outcome: a systematic review and meta-analysis.

Background: Despite its effectiveness, the standard course of chemoradiation for the treatment of human papillomavirus (HPV)-related oropharyngeal carcinoma (OPC) results in considerable treatment-related adverse effects. Studies proved that HPV-positive OPC is very sensitive to radiotherapy. Using de-escalation therapy as a new strategy is critical to maintaining positive outcomes while alleviating side effects. However, some studies hold that reduced dose causes insufficient effect on tumor killing. We conducted this systematic review and meta-analysis of survival and adverse reactions in patients with HPV-related OPC by retrospective analysis and evaluated the therapeutic effect of reducing the radiation dose. Methods: Data were double-selected and extracted by searching seven electronic databases, Original studies in all language treated HPV-associated OPC with reduced-dose and standard-dose therapies were included. Overall survival (OS), progression-free survival (PFS), and incidence rates of adverse events were obtained by pooling analyses. Statistical analyses were performed using RStudio Version 1.1.383 (RStudio, Boston, MA, USA) via the Meta-Analysis R Package (metafor). Heterogeneity was evaluated using the I2 statistic and the Cochran Q test. We used Stata (version 15.0) for forest graph. Results: Thirteen studies were included in this meta-analysis, involving a dose range of 66-70 Gy for the standard treatment regimen and <66 Gy for the reduced-dose group. There was no significant difference in the age of the patients in the standard and the reduced treatment groups (60.9±5.9 vs. 58.6±2.4 years). Nine studies were included as standard cohort and thirteen studies were enrolled as reduced-dose cohort. The 2- and 3-year overall survival rates in the reduced-dose group (95.66% and 91.51%, respectively) were superior to those in the standard-dose group (88.36% and 87.46%, respectively). There was no significant difference in PFS between the two groups. A systematic review of articles on dose reduction and the standard dose was also conducted. The most common complication in reduced-dose radiation was oral mucositis (36.4%), followed by decreased white blood cell (WBC) count (30.5%) and dry mouth (29.1%). Conclusions: Reducing the radiation dose in patients with HPV-related OPC substantially alleviates the treatment toxicities and optimizes the quality of life of patients while at the same time maintaining favorable oncologic outcomes.

Apurinic/apyrimidinic endonuclease 1/reduction-oxidation effector factor-1 (APE1) regulates the expression of NLR family pyrin domain containing 3 (NLRP3) inflammasome through modulating transcription factor NF-κB and promoting the secretion of inflammatory mediators in macrophages.

BACKGROUND: Inflammatory mediators play an important role in the occurrence, development, and metastasis of tumors. The aim of the present study was to elucidate the effect of apurinic/apyrimidinic endonuclease 1/reduction-oxidation effector factor-1 (APE1) on inflammatory mediator secretion, which is dependent on the APE1-mediated NLR family pyrin domain containing 3 (NLRP3) regulatory mechanism. METHODS: The human myeloid leukemia mononuclear cell line (THP-1) cells were cultured and polarized to M2 subset macrophages. Enzyme-linked immunosorbent assay was used for determining tumor necrosis factor-α (TNF-α), interleukin (IL)-1ß, IL-18, IL-10, and IL-33 levels. Reverse transcription-polymerase chain reaction and western blot were used for evaluating TNF-α, NLR family pyrin domain containing 1 (NLRP1), NLRP3, caspase-1, and apoptosis-associated speck-like protein containing a card expression. Plasmid silencing APE1 gene (APE1shRNA) was synthesized and packaged into lentiviral. For activating inflammasomes, M2-type THP-1 cells were transfected with lentiviral vector APE1shRNA incubated with lipopolysaccharide (LPS) (100 ng/mL)/APE1 inhibitor (E3330, 20 µM) and ATP. Electrophoretic mobility shift assay and dual-luciferase reporter assay were used for determining the interaction between NLRP3 and nuclear factor-κB (NF-κB) molecule. RESULTS: APE1 significantly induced LPS-induced pro-inflammatory cytokine production, including TNF-α, IL-1ß, and IL18, compared with THP-1 cells without APE1 treatment (P<0.05). APE1 promoted LPS-induced NLRP3 inflammasome activation by modulating the gene transcription of NLRP3-associated molecules. APE1 enhanced LPS-induced NLRP3 inflammasome activation by regulating NLRP3 and caspase-1 protein expression. APE1 improved NLRP3 activity by modulating the interaction between NLRP3 and NF-κB, and the modulation of NF-κB. APE1 promoted LPS-induced NLRP3 inflammasome activation through an NF-κB-dependent pathway. CONCLUSIONS: APE1 regulates the expression of NLRP3 by modulating transcription factor NF-κB and further promoting the secretion of inflammatory mediators IL-1ß and IL-18 in macrophages. The findings of the present study provide theoretical and experimental bases for the design of tumor-associated macrophage (TAM)-targeted therapy, with APE1 as the target molecule.

Transcriptional E2F1/2/3/6 as potential prognostic biomarkers in cutaneous melanoma.

Although the abnormal expression of members of the E2F family has been reported to participate in carcinogenesis in many human types of cancer, the bioinformatics role of the E2F family in melanoma is unknown. This research was designed to detect the expression, methylation, prognostic value and potential effects of the E2F family in melanoma. We investigated E2F family mRNA expression from the Oncomine and GEPIA databases and their methylation status in the MethHC database. Meanwhile, we detected the relative E2F family expression levels by qPCR and immunohistochemistry. Kaplan-Meier Plotter was used to draw survival analysis charts, and gene functional enrichment analyses were applied through cBioPortal database analysis. E2F1/2/3/4/5/6 mRNA and proteins were clearly upregulated in cutaneous melanoma patients, and high expression levels of E2F1/2/3/6 were statistically related to high methylation levels. Increased mRNA expression of E2F1/2/3/6 was related to lower overall survival rates (OS) and disease-free survival (DFS) in cutaneous melanoma cases. Meanwhile, E2F1/2/3/6 carried out these effects through regulating multiple signaling pathways, including the MAPK, PI3K-Akt and p53 signaling pathways. Taking together, our findings suggest that E2F1/2/3/6 could act as potential targets for precision therapy in cutaneous melanoma patients.

Impact of high-dose rate radiotherapy on B and natural killer (NK) cell polarization in peripheral blood mononuclear cells (PBMCs) via inducing non-small cell lung cancer (NSCLC)-derived exosomes.

BACKGROUND: Non-small cell lung cancer (NSCLC) is the most commonly diagnosed solid tumor. While it has been established that stereotactic body radiotherapy for NSCLC plays an important role in antitumor immune response, the possible effects of the dose rate on this response has not been fully clarified. METHODS: In vitro, A549 cells were irradiated on a Varian TrueBeam® Linear Accelerator with dose and dose rate escalation using the flattening filter-free (FFF) technique, which was followed by coculturing with peripheral blood mononuclear cells (PBMCs). The exosomes from irradiated A549 cells were isolated and then cocultured with PBMCs. Flow cytometry was performed to analyze the proportion of lymph cell clusters in PBMCs. RESULTS: The proportion of CD3- immune cell clusters in PBMCs was significantly higher in the 10 Gy treatment group than in the nonirradiated group and other lower-dose (2, 6 Gy) treatment groups at the dose rate of 1,000 MU/min. However, no influence was observed on the proportion of CD3+ T cell subsets. Further results showed that both natural killer (NK) and B cell proportions reached peaks in the 14 Gy treatment group when a dose rate of 1,200 MU/min was used. Notably, the peak values of these two cell proportions were reached at a lower radiation dose of 10 Gy when a greater dose rate, ranging from 1,600 to 2,400 MU/min, was used. We further found that a single, high dose of irradiation (10 Gy), as compared with a single, low dose of irradiation (2 Gy), could markedly stimulate the A549-related exosome secretion in a radiation dose rate-dependent manner. The ultrahigh dose rate radiation-derived exosomes contributed to the polarization of B and NK cell subsets in PBMCs. CONCLUSIONS: The optimized radiation regime, which depends on the appropriate radiation dose and dose rate, results in the production of exosomes derived from NSCLC cells and eventually the redistribution of immune cells in PBMCs.

Association of Epstein-Barr virus infection with peripheral immune parameters and clinical outcome in advanced nasopharyngeal carcinoma.

The purpose of this study was to investigate the association of Epstein-Barr virus (EBV) with peripheral blood immune cell counts and clinical outcomes in advanced nasopharyngeal carcinoma (NPC) patients. In a retrospective design, 146 patients with NPC at stage IV were enrolled in this study. The association of EBV status with peripheral blood immune cell counts, distant metastases, and long-term survival in patients with advanced NPC were determined. Eighty-seven (59.6%) of all patients were positive for EBV. Compared with patients with normal NK cell count, patients with lower NK cell count showed a significantly lower EBV viral load (median: 614.0 vs. 2190.0 copies/mL, P = 0.024). EBV-positive patients showed a significantly higher incidence of liver metastasis than EBV-negative patients (32.6% vs. 23.7%, P = 0.021). Multi-variant regression analysis showed that EBV infection was independently associated with liver metastasis (OR: 2.33, P = 0.043). EBV positive patients showed a significantly worse PFS (P = 0.001) and OS (P = 0.001) than EBV negative patients. Multivariate Cox regression analysis revealed that EBV infection was independently associated with a worse PFS (HR: 1.94, P = 0.003), and OS (HR: 2.12, P = 0.014) in advanced NPC. In conclusion, EBV infection is associated with a high risk of liver metastasis and is also an independent negative predictor for PFS and OS in patients with advanced NPC. EBV infection is associated with lower CD8% and higher NK%, while lower NK cell count is associated with lower EBV viral load.

Risk of hematologic toxicities with programmed cell death-1 inhibitors in cancer patients: a meta-analysis of current studies.

BACKGROUND: Programmed cell death-1 (PD-1) inhibitor-related hematologic toxicities are a category of rare but clinically serious and potentially life-threatening adverse events; however, little is known about their risks across different treatment regimens and tumor types. The objective of this study was to compare the incidences of PD-1 inhibitor-related hematologic toxicities among different therapeutic regimens and tumor types. METHODS: Twenty-six original articles on PD-1 inhibitor trials were identified based on a PubMed search completed on September 26, 2017. The incidences of hematologic toxicities were collected. RESULTS: A total of 26 studies containing 5,088 patients were included in the meta-analysis. PD-1 inhibitor monotherapy was associated with an increased risk of all-grade anemia in cancer patients (5%, 95% CI 4%-6%), particularly in patients with renal cell carcinoma (RCC) (8%, 95% CI 6%-12%), compared with all-grade thrombocytopenia (2%, 95% CI 1%-5%), leukopenia (2%, 95% CI 1%-3%), and neutropenia (1%, 95% CI 0-1%). However, low incidences of high-grade hematologic toxicities were observed in cancer patients treated with PD-1 inhibitor monotherapy. The use of PD-1 inhibitors in combination with ipilimumab, peptide vaccines, or chemotherapy had significantly higher risks than PD-1 inhibitor monotherapy for all-grade anemia (13%, 95% CI 5%-31%), thrombocytopenia (6%, 95% CI 2%-18%), leukopenia (5%, 95% CI 1%-35%), neutropenia (4%, 95% CI 1%-26%), and only high-grade thrombocytopenia (4%, 95% CI 1%-15%). In addition, all-grade and high-grade hematologic toxicities in chemotherapy and everolimus treatment arms were more frequent than in PD-1 inhibitor monotherapy arms. CONCLUSION: The risks of PD-1 inhibitor-related hematologic toxicities were higher in RCC than in other cancers, and during combination therapy. These results may contribute toward enhancing awareness among clinicians about frequent clinical monitoring when managing PD-1 inhibitors.

Apurinic/apyrimidinic endonuclease 1 regulates angiogenesis in a transforming growth factor ß-dependent manner in human osteosarcoma.

Angiogenesis plays an important role in tumor growth and metastasis and has been reported to be inversely correlated with overall survival of osteosarcoma patients. It has been shown that apurinic/apyrimidinic endonuclease 1 (APE1), a dually functional protein possessing both base excision repair and redox activities, is involved in tumor angiogenesis, although these mechanisms are not fully understood. Our previous study showed that the expression of transforming growth factor ß (TGFß) was significantly reduced in APE1-deficient osteosarcoma cells. Transforming growth factor ß promotes cancer metastasis through various mechanisms including immunosuppression, angiogenesis, and invasion. In the current study, we initially revealed that APE1, TGFß, and microvessel density (MVD) have pairwise correlation in osteosarcoma tissue samples, whereas TGFß, tumor size, and MVD were inversely related to the prognosis of the cohort. We found that knocking down APE1 in osteosarcoma cells resulted in TGFß downregulation. In addition, APE1-siRNA led to suppression of angiogenesis in vitro based on HUVECs in Transwell and Matrigel tube formation assays. Reduced secretory protein level of TGFß of culture medium also resulted in decreased phosphorylation of Smad3 of HUVECs. In a mouse xenograft model, siRNA-mediated silencing of APE1 downregulated TGFß expression, tumor size, and MVD. Collectively, the current evidence indicates that APE1 regulates angiogenesis in osteosarcoma by controlling the TGFß pathway, suggesting a novel target for anti-angiogenesis therapy in human osteosarcoma.

DNA-PKcs phosphorylates hnRNP-A1 to facilitate the RPA-to-POT1 switch and telomere capping after replication.

The heterogeneous nuclear ribonucleoprotein A1 (hnRNP-A1) has been implicated in telomere protection and telomerase activation. Recent evidence has further demonstrated that hnRNP-A1 plays a crucial role in maintaining newly replicated telomeric 3' overhangs and facilitating the switch from replication protein A (RPA) to protection of telomeres 1 (POT1). The role of hnRNP-A1 in telomere protection also involves DNA-dependent protein kinase catalytic subunit (DNA-PKcs), although the detailed regulation mechanism has not been clear. Here we report that hnRNP-A1 is phosphorylated by DNA-PKcs during the G2 and M phases and that DNA-PK-dependent hnRNP-A1 phosphorylation promotes the RPA-to-POT1 switch on telomeric single-stranded 3' overhangs. Consequently, in cells lacking hnRNP-A1 or DNA-PKcs-dependent hnRNP-A1 phosphorylation, impairment of the RPA-to-POT1 switch results in DNA damage response at telomeres during mitosis as well as induction of fragile telomeres. Taken together, our results indicate that DNA-PKcs-dependent hnRNP-A1 phosphorylation is critical for capping of the newly replicated telomeres and prevention of telomeric aberrations.

Functional analysis of tanshinone IIA that blocks the redox function of human apurinic/apyrimidinic endonuclease 1/redox factor-1.

Apurinic/apyrimidinic endonuclease 1/redox factor-1 (APE1/Ref-1) is a multifunctional protein possessing both DNA repair and redox regulatory activities. It has been shown that blocking redox function leads to genotoxic, antiangiogenic, cytostatic, and proapoptotic effects in cells. Therefore, the selective inhibitors against APE1's redox function can be served as potential pharmaceutical candidates in cancer therapeutics. In the present study, we identified the biological specificity of the Chinese herbal compound tanshinone IIA (T2A) in blocking the redox function of APE1. Using dual polarization interferometry, the direct interaction between APE1 and T2A was observed with a KD value at subnanomolar level. In addition, we showed that T2A significantly compromised the growth of human cervical cancer and colon cancer cells. Furthermore, the growth-inhibitory or proapoptotic effect of T2A was diminished in APE1 knockdown or redox-deficient cells, suggesting that the cytostatic effect of T2A might be specifically through inhibiting the redox function of APE1. Finally, T2A pretreatment enhanced the cytotoxicity of ionizing radiation or other chemotherapeutic agents in human cervical cancer and colon cancer cell lines. The data presented herein suggest T2A as a promising bioactive inhibitor of APE1 redox activity.

Identification of a novel potential antitumor activity of gossypol as an APE1/Ref-1 inhibitor.

The human apurinic/apyrimidinic endonuclease 1/redox enhancing factor-1 (APE1/Ref-1), an essential multifunctional protein involved in the repair of oxidative deoxyribonucleic acid (DNA) damage and transcriptional regulation, is often overexpressed in tumor tissues and cancer cells. Moreover, APE1/Ref-1 (APE1) overexpression has been linked to chemoresistance in human tumors. Thus, inhibiting APE1 function in cancer cells is considered a promising strategy to overcome resistance to therapeutic agents. Gossypol is a Bcl-2 homology 3 (BH3)-mimetic agent and is able to bind to the BH3 domain of B-cell lymphoma 2 (Bcl-2) family members. Other studies demonstrated that Bcl-2 directly interacted with APE1 via its BH domains. Using apurinic/apyrimidinic (AP) endonuclease assays, we found that gossypol inhibits the repair activity of APE1. Electrophoretic mobility shift assays and dual luciferase assays showed that gossypol could also inhibit the redox function of APE1. Using dual polarization interferometry technology, we show that gossypol can directly interact with APE1. Furthermore, addition of gossypol, in conjunction with APE1 overexpression, leads to cancer cell death. The addition of gossypol also enhances the cell killing effect of the laboratory alkylating agent methyl methanesulfonate and the clinical agent cisplatin (DDP). Administration of gossypol significantly inhibited the growth of xenografts. Furthermore, the combined treatment of gossypol and DDP resulted in a statistically higher antitumor activity compared with DDP alone in vivo. In conclusion, we have demonstrated that gossypol effectively inhibits the repair and redox activity of APE1 through a direct interaction.

APE1/Ref-1 enhances DNA binding activity of mutant p53 in a redox-dependent manner.

Apurinic/apyrimidinic endonuclease 1/redox factor-1 (APE1/Ref-1) is a dual function protein; in addition to its DNA repair activity, it can stimulate DNA binding activity of numerous transcription factors as a reduction-oxidation (redox) factor. APE1/Ref-1 has been found to be a potent activator of wild-type p53 (wtp53) DNA binding in vitro and in vivo. Although p53 is mutated in most types of human cancer including hepatocellular carcinoma (HCC), little is known about whether APE1/Ref-1 can regulate mutant p53 (mutp53). Herein, we reported the increased APE1/Ref-1 protein and accumulation of mutp53 in HCC by immunohistochemistry. Of note, it was observed that APE1/Ref-1 high-expression and mutp53 expression were associated with carcinogenesis and progression of HCC. To determine whether APE1/Ref-1 regulates DNA binding of mutp53, we performed electromobility shift assays (EMSAs) and quantitative chromatin immunoprecipitation (ChIP) assays in HCC cell lines. In contrast to sequence-specific and DNA structure-dependent binding of wtp53, reduced mutp53 efficiently bound to nonlinear DNA, but not to linear DNA. Notably, overexpression of APE1/Ref-1 resulted in increased DNA binding activity of mutp53, while downregulation of APE1/Ref-1 caused a marked decrease of mutp53 DNA binding. In addition, APE1/Ref-1 could not potentiate the accumulation of p21 mRNA and protein in mutp53 cells. These data indicate that APE1/Ref-1 can stimulate mutp53 DNA binding in a redox-dependent manner.

Human apurinic/apyrimidinic endonuclease siRNA inhibits the angiogenesis induced by X-ray irradiation in lung cancer cells.

OBJECTIVE: Radiotherapy is an important and effective treatment method for non-small cell lung cancer (NSCLC). Nonetheless, radiotherapy can alter the expression of proangiogenic molecules and induce angiogenesis. Human apurinic/apyrimidinic endonuclease (APE1) is a multifunctional protein, which has DNA repair and redox function. Our previous studies indicated APE1 is also a crucial angiogenic regulator. Thus, we investigated the effect of APE1 on radiation-induced angiogenesis in lung cancer and its underlying mechanism. METHODS: Tumor specimens of 136 patients with NSCLC were obtained from 2003 to 2008. The APE1 and vascular endothelial growth factor (VEGF) expression, as well as microvessel density (MVD) were observed with immunohistochemistry in tumor samples. Human lung adenocarcinoma A549 cells were treated with Ad5/F35-APE1 siRNA and/or irradiation, and then the cells were used for APE1 analysis by Western blot and VEGF analysis by RT-PCR and ELISA. To elucidate the underline mechanism of APE1 on VEGF expression, HIF-1α protein level was determined by Western blot, and the DNA binding activity of HIF-1α was detected by EMSA. Transwell migration assay and capillary-like structure assay were used to observe the migration and capillary-like structure formation ability of human umbilical veins endothelial cells (HUVECs) that were co-cultured with Ad5/F35-APE1 siRNA and (or) irradiation treated A549 cells culture medium. RESULTS: The high expression rates of APE1 and VEGF in NSCLC were 77.94% and 66.18%, respectively. The expressions of APE1 was significantly correlated with VEGF and MVD (r=0.369, r=0.387). APE1 and VEGF high expression were significantly associated with reduced disease free survival (DFS) time. The high expressions of APE1 and VEGF on A549 cells were concurrently induced by X-ray irradiation in a dose-dependent manner. Silencing of APE1 by Ad5/F35-APE1 siRNA significantly decreased DNA binding activity of HIF-1α and suppressed the expression of VEGF in A549 cells, moreover, significantly inhibited the endothelial cells immigration and capillary-like structure formation induced by irradiated A549 cells. CONCLUSION: Our results indicate that APE1 may play a crucial role in angiogenesis induced by irradiation. Administration of Ad5/F35-APE1 siRNA during radiotherapy could be a potent adjuvant therapeutic approach to enhance the radiotherapy response, effectively eliminate metastasis and improve the efficacy of radiotherapy for NSCLC.

Silencing of APE1 enhances sensitivity of human hepatocellular carcinoma cells to radiotherapy in vitro and in a xenograft model.

Resistance to radiotherapy is a key limitation for the treatment of human hepatocellular carcinoma (HCC). To overcome this problem, we investigated the correlation between radioresistance and the human apurinic/apyrimidinic endonuclease (APE1), a bifunctional protein, which plays an important role in DNA repair and redox regulation activity of transcription factors. In the present study, we examined the radiosensitivity profiles of three human HCC cell lines, HepG2, Hep3B, and MHCC97L, using the adenoviral vector Ad5/F35-mediated APE1 siRNA (Ad5/F35-siAPE1). The p53 mutant cell lines MHCC97L showed radioresistance, compared with HepG2 and Hep3B cells. APE1 was strongly expressed in MHCC97L cells and was induced by irradiation in a dose-dependent manner, and Ad5/F35-siAPE1 effectively inhibited irradiation-induced APE1 and p53 expression. Moreover, silencing of APE1 significantly potentiated the growth inhibition and apoptosis induction by irradiation in all tested human HCC cell lines. In addition, Ad5/F35-siAPE1 significantly enhanced inhibition of tumor growth and potentiated cell apoptosis by irradiation both in HepG2 and MHCC97L xenografts. In conclusion, down regulation of APE1 could enhance sensitivity of human HCC cells to radiotherapy in vitro and in vivo.