Nimotuzumab enhances the radiosensitivity of cancer cells in vitro by inhibiting radiation-induced DNA damage repair

Research progress in MCM family: Focus on the tumor treatment resistance

Malignant tumors constitute a significant category of diseases posing a severe threat to human survival and health, thereby representing one of the most challenging and pressing issues in the field of biomedical research. Due to their malignant nature, which is characterized by a high potential for metastasis, rapid dissemination, and frequent recurrence, the prevailing approach in clinical oncology involves a comprehensive treatment strategy that combines surgery with radiotherapy, chemotherapy, targeted drug therapies, and other interventions. Treatment resistance remains a major obstacle in the comprehensive management of tumors, serving as a primary cause for the failure of integrated tumor therapies and a critical factor contributing to patient relapse and mortality. The Minichromosome Maintenance (MCM) protein family comprises functional proteins closely associated with the development of resistance in tumor therapy.The influence of MCMs manifests through various pathways, encompassing modulation of DNA replication, cell cycle regulation, and DNA damage repair mechanisms. Consequently, this leads to an enhanced tolerance of tumor cells to chemotherapy, targeted drugs, and radiation. Consequently, this review explores the specific roles of the MCM family in various cancer treatment strategies. Its objective is to enhance our comprehension of resistance mechanisms in tumor therapy, thereby presenting novel targets for clinical research aimed at overcoming resistance in cancer treatment. This bears substantial clinical relevance.

Efficacy and survival analysis of nimotuzumab combined with concurrent chemoradiotherapy in the treatment of locally advanced nasopharyngeal carcinoma

Objective

This study investigated the curative effect of adding nimotuzumab (NTZ) in patients with locally advanced nasopharyngeal carcinoma (NPC) who were treated with concurrent chemoradiotherapy (CCRT) and explored significant prognostic factors of NPC.

Materials and methods

The clinical data of 307 patients with NPC treated in the First Affiliated Hospital of Soochow University from January 2013 to December 2018 were retrospectively analyzed. The patients were divided into the NTZ-CCRT group and the CCRT group according to whether they were associated with NTZ. We applied propensity score matching to reduce the interference of biases and compared the short-term efficacy and long-term survival rate of the two groups. Moreover, univariate and multivariate analyses were performed for all patients, and subgroup analysis was used to compare the efficacy of therapy combined with NTZ in different subgroups.

Results

In primary nasopharyngeal tumors, the objective response rates in the NTZ-CCRT group and CCRT group were 95.8% and 85.7%, respectively (P =0.007). In cervical positive lymph nodes, the objective response rates in the NTZ-CCRT group and CCRT group were 98.3% and 87.4%, respectively (P =0.001). Compared with CCRT alone, the addition of NTZ significantly improved the 5-year OS (94.1% vs. 81.8%, P=0.014) and the 5-year DFS (84.2% vs. 75.5%, P=0.031) of NPC patients; however, the addition of NTZ was accompanied by more severe hematologic toxicity and acute oral mucositis. Multivariate analysis demonstrated that the addition of NTZ was an important prognostic factor for OS and DFS (HR 0.367, 95% CI 0.167-0.808, P=0.013 for OS and HR 0.536, 95% CI 0.312-0.919, P=0.023 for DFS) and the level of pretreatment LDH (HR 5.170, 95% CI 2.125-12.580, P<0.001 for OS and HR 2.421, 95% CI 1.027-5.707, P=0.043 for DFS). Moreover, patients with high levels of hsCRP before treatment (HR 0.389, 95% CI 0.177-0.853, P=0.018) may gain more benefits from combined treatment with NTZ.

Conclusions

For locally advanced NPC patients treated with concurrent chemoradiotherapy, the addition of NTZ can significantly improve their survival outcome. However, it is necessary to guard against the associated increase in hematological toxicity and acute oral mucositis.

Survival comparison between postoperative and preoperative radiotherapy for stage I-III non-inflammatory breast cancer

To compare the survival benefit between preoperative and postoperative radiotherapy for stage I-III non-inflammatory breast cancer patients, we conducted a retrospective cohort study using surveillance, epidemiology and end results databases. Our study recruited patients who had been diagnosed with stage I-III breast cancer and underwent surgery and radiotherapy. The overall survival was calculated by Kaplan-Meier method. Cox risk model was used to determine the impact of radiotherapy according to stage, molecular subtype and other risk factors. Propensity score matching was used to balance measurable confounding factors. Of all the 411,279 enrolled patients varying from 1975 to 2016, 1712 patients received preoperative radiotherapy, and 409,567 patients received postoperative radiotherapy. Compared with the postoperative radiotherapy group, the preoperative radiotherapy group showed significantly higher risks of overall mortality and breast cancer-specific mortality. Survival differences in treatment sequences were correlated with stage, molecular subtypes and other risk factors. According to the results of this study, preoperative radiotherapy did not show a survival advantage, and postoperative radiotherapy is still the primary treatment. However, preoperative radiotherapy also has some theoretical advantages, such as phase reduction and recurrence reduction. Therefore, it is still worthy of further exploration.

Comparison of radiotherapy combined with nimotuzumab vs. chemoradiotherapy for locally recurrent nasopharyngeal carcinoma

BACKGROUND

The present study compared the effectiveness and toxicity of two treatment modalities, namely radiotherapy combined with nimotuzumab (N) and chemoradiotherapy (CRT) in patients with locally recurrent nasopharyngeal carcinoma (LR-NPC).

METHODS

Patients with LR-NPC who were treated with radiotherapy were retrospectively enrolled from January 2015 to December 2018. The treatment included radiotherapy combined with N or platinum-based induction chemotherapy and/or concurrent chemotherapy. The comparison of survival and toxicity between the two treatment modalities was evaluated using the log-rank and chi-squared tests. Overall survival (OS) was the primary endpoint.

RESULTS

A total of 87 patients were included, of whom 32 and 55 were divided into the N group and the CRT group, respectively. No significant differences were noted in the survival rate between the N and the CRT groups (4-year OS rates, 37.1% vs. 40.7%, respectively; P = 0.735). Mild to moderate acute complications were common during the radiation period and mainly included mucositis and xerostomia. The majority of the acute toxic reactions were tolerated well. A total of 48 patients (55.2%) demonstrated late radiation injuries of grade ≥ 3, including 12 patients (37.5%) in the N group and 36 patients (66.5%) in the CRT group. The CRT group exhibited significantly higher incidence of severe late radiation injuries compared with that of the N group (P = 0.011).

CONCLUSION

Radiotherapy combined with N did not appear to enhance treatment efficacy compared with CRT in patients with LR-NPC. However, radiotherapy combined with N may be superior to CRT due to its lower incidence of acute and late toxicities. Further studies are required to confirm the current findings.

Targeted and systemic insights into the crosstalk between DNA-dependent protein kinase catalytic subunit and receptors of estrogen, progesterone and epidermal growth factor in the context of cancer

DNA-dependent protein kinase catalytic subunit (DNA-PKcs) has emerged as a regulator of carcinogenesis. Increased expression of DNA-PKcs correlates with metastatic cancers. Here we review recently reported crosstalk of DNA-PKcs with estrogen (ER), progesterone (PR) and epidermal growth factor (EGFR) receptors. The reports show an extensive network of functional and direct interactions. Targeted studies focused on specific molecular mechanisms, and a systems biology network analysis shows unbiasedly engagement of various cellular functions. Feedforward regulation between expression and activities of DNA-PKcs and ER, DNA-PKcs-dependent phosphorylation of PR and an impact on PR-dependent transcription, and DNA-PKcs-promoted EGFR-dependent aggressiveness and metastases are examples of the results of targeted studies. Systems biology approach extracted many more genes and proteins engaged by DNA-PKcs in interaction with ER, PR, and EGFR. Examples are such regulators and predictors of breast tumorigenesis as BRCA1, TP53, and 18 genes of the MammaPrint signature. Reviewed here data suggest that the diagnostic value of DNA-PKcs in the context of ER, PR and EGFR signaling is defined by a network signature rather than by single markers. This review summarizes mechanisms of DNA-PKcs interaction with ER, PR, and EGFR, highlights tumor suppressors and oncogenes engaged by DNA-PKcs, and emphasizes the importance of diagnostic network-based signatures.

The Importance of Being PI3K in the RAS Signaling Network

Ras proteins are essential mediators of a multitude of cellular processes, and its deregulation is frequently associated with cancer appearance, progression, and metastasis. Ras-driven cancers are usually aggressive and difficult to treat. Although the recent Food and Drug Administration (FDA) approval of the first Ras G12C inhibitor is an important milestone, only a small percentage of patients will benefit from it. A better understanding of the context in which Ras operates in different tumor types and the outcomes mediated by each effector pathway may help to identify additional strategies and targets to treat Ras-driven tumors. Evidence emerging in recent years suggests that both oncogenic Ras signaling in tumor cells and non-oncogenic Ras signaling in stromal cells play an essential role in cancer. PI3K is one of the main Ras effectors, regulating important cellular processes such as cell viability or resistance to therapy or angiogenesis upon oncogenic Ras activation. In this review, we will summarize recent advances in the understanding of Ras-dependent activation of PI3K both in physiological conditions and cancer, with a focus on how this signaling pathway contributes to the formation of a tumor stroma that promotes tumor cell proliferation, migration, and spread.

Efficacy and safety of nimotuzumab in unresectable, recurrent, and/or metastatic squamous cell carcinoma of the head and neck: A hospital-based retrospective evidence

Context:

Role of nimotuzumab in locally advanced head and neck cancer (HNC) is well established in India; however, no clinical evidence is available for its role in recurrent and/or metastatic HNC.

Aims:

The aim of this study is to evaluate the efficacy and safety of nimotuzumab when added to standard treatment in unresectable, recurrent, and metastatic squamous cell carcinoma of the head and neck (SCCHN).

Settings and Design:

Hospital records of 14 patients diagnosed with recurrent and/or metastatic HNC with histologically confirmed squamous cell carcinoma and being treated with nimotuzumab along with standard treatments from December 2010 to December 2016 were retrospectively evaluated.

Subjects and Methods:

The tumor response rate and overall survival (OS) were analyzed. Toxicity and adverse events (AEs) were assessed as per common terminology criteria for adverse events (CTCAE) v 4.

Results:

Oral cavity was most commonly involved region followed by hypopharynx and oropharynx. At 24 weeks after completion of treatment, overall response rate (complete response (CR) + partial response (PR)) was 75%. Survival rate at 1, 2, and 3 years was 77.80%, 64.81%, and 64.81%, respectively. At a median follow-up of 15.17 months, median OS was not reached. All AEs were either Grade I (66.7%) or Grade II (33.3%). No Grade III or Grade IV AEs were observed. No added toxicity was observed due to nimotuzumab.

Conclusions:

In the first of its kind study, the addition of nimotuzumab to standard treatment showed promising response rate as well as survival outcomes in recurrent and/or metastatic SCCHN patients without producing additional toxicity.

Efficacy and safety of concurrent chemoradiotherapy with or without Nimotuzumab in unresectable locally advanced squamous cell carcinoma of head and neck: Prospective comparative study - ESCORT-N study

Background:

Nimotuzumab is an anti-epidermal growth factor receptor monoclonal antibody which can be added to chemoradiotherapy (CRT) to improve efficacy for management of locally advanced squamous cell carcinoma of the head and neck (LASCCHN). We prospectively evaluated the efficacy and safety of nimotuzumab with CRT for LASCCHN and compared with CRT alone.

Materials and Methods:

In this prospective study, 29 LASCCHN (Stage III–IVb) patients received Nimotuzumab plus CRT or CRT alone. Treatment included six cycles of cisplatin (40–50 mg/week) or carboplatin (area under the curve-based), nimotuzumab (200 mg/week), and radiotherapy (60–70 Gy). Tumor response was evaluated as per response evaluation criteria in solid tumors criteria. MoS was estimated using the Kaplan–Meier method. Toxicity and adverse events (AE's) were assessed as per CTCAE v 4.0.

Results:

At 24 weeks after completion of treatment, the tumor response rate (complete response, partial response, stable disease) was 53.3% and 35.7% favoring nimotuzumab arm while progression of disease was 40% and 35.7% in Nimotuzumab plus CRT and CRT groups, respectively. However, the objective response rate was 57% and 30% in favor of nimotuzumab arm. At median follow-up of 45.5 months, MoS was 33 months in Nimotuzumab plus CRT and 27 months in CRT group. The 5-year survival rate was 33.3% in Nimotuzumab plus CRT versus 7.1% in CRT group. Nimotuzumab was observed to be safe with no additional AE's such as hypersensitivity, hypomagnesemia, and allergic reaction was reported.

Conclusion:

Addition of Nimotuzumab to standard CRT showed improved survival rate in unresectable, LASCCHN patients without producing additional toxicity.

PBA2, a novel compound, enhances radiosensitivity in various carcinoma cells by activating the p53 pathway in vitro and in vivo

Radiotherapy is the main method used to treat human carcinoma; however, certain types of carcinomas are radiation-insensitive. The present study aimed to explore whether a novel compound, PBA2, could enhance the radiosensitivity of various carcinoma cells in vitro and in vivo, and investigate its underlying mechanism. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was used to assess the cytotoxicity of PBA2. Colony formation assays were used to observe the radiosensitivity effect of PBA2 in vitro. Cell cycle distributions and cell apoptosis were estimated using flow cytometry. Comet assays and Immunofluorescence assays were used to analyze DNA damage. The intracellular RNA was extracted and analyzed by sequencing. Western blotting was used to determine protein levels. A stable cell line with TP53 (encoding p53) knockdown was constructed by cell transfection. A mouse xenograft model was used to assess the radiosensitivity effect of PBA2 in vivo. We found that PBA2 at a low concentration (0.1 μM) enhanced radiosensitivity in various carcinoma cells, including CNE1, MG63, KB, HEP2, GLC82, and SMMC7221, in vitro. Combined with PBA2, radiation induced significant cell apoptosis in CNE1 and MG63 cells, accompanied by increased DNA damage, but did not affect cell cycle arrest. Mechanistically, PBA2 promoted p53 expression significantly; however, when p53 was mutated, functionally impaired, or knocked down, PBA2 could not enhance the radiosensitivity of these cells. Additionally, the combination of PBA2 and radiation reduced the tumor volume and tumor weight in CNE1 xenograft models significantly, without obvious toxicities. Our results demonstrated that PBA2 enhanced the radiosensitivity of various carcinoma cells in vitro and in vivo. The underlying mechanism might involve increasing DNA damage and cell apoptosis via activating the p53 pathway.

The Roles of Autophagy and Senescence in the Tumor Cell Response to Radiation

Radiation is a critical pillar in cancer therapeutics, exerting its anti-tumor DNA-damaging effects through various direct and indirect mechanisms. Radiation has served as an effective mode of treatment for a number of cancer types, providing both curative and palliative treatment; however, resistance to therapy persists as a fundamental limitation. While cancer cell death is the ideal outcome of any anti-tumor treatment, radiation induces several responses, including apoptotic cell death, mitotic catastrophe, autophagy and senescence, where autophagy and senescence may promote cell survival. In most cases, autophagy, a conventionally cytoprotective mechanism, is a "first" responder to damage incurred from chemotherapy and radiation treatment. The paradigm developed on the premise that autophagy is cytoprotective in nature has provided the rationale for current clinical trials designed with the goal of radiosensitizing cancer cells through the use of autophagy inhibitors; however, these have failed to produce consistent results. Delving further into pre-clinical studies, autophagy has actually been shown to take diverse, sometimes opposing, forms, such as acting in a cytotoxic or nonprotective fashion, which may be partially responsible for the inconsistency of clinical outcomes. Furthermore, autophagy can have both pro- and anti-tumorigenic effects, while also having an important immune modulatory function. Senescence often occurs in tandem with autophagy, which is also the case with radiation. Radiation-induced senescence is frequently followed by a phase of proliferative recovery in a subset of cells and has been proposed as a tumor dormancy model, which can contribute to resistance to therapy and possibly also disease recurrence. Senescence induction is often accompanied by a unique secretory phenotype that can either promote or suppress immune functions, depending on the expression profile of cytokines and chemokines. Novel therapeutics selectively cytotoxic to senescent cells (senolytics) may prove to prolong remission by delaying disease recurrence in patients. Accurate assessment of primary responses to radiation may provide potential targets that can be manipulated for therapeutic benefit to sensitize cancer cells to radiotherapy, while sparing normal tissue.

Induction of different cellular arrest and molecular responses in low EGFR expressing A549 and high EGFR expressing A431 tumor cells treated with various doses of 177Lu-Nimotuzumab

INTRODUCTION

Radioimmunotherapy (RIT) is a major anti-cancer therapy in cancer management multimodalities. ¹⁷⁷Lu-Nimotuzumab has been in the use for radioimmunotherapy of EGFR expressing tumors. This study focuses on understanding the differential cellular and molecular mechanisms of anti-tumor effects of ¹⁷⁷Lu-Nimotuzumab on low EGFR expressing A549 and high EGFR expressing A431 tumor cells.

MATERIALS AND METHODS

Nimotuzumab labeled with ¹⁷⁷Lu was characterized by SE-HPLC. Specificity of ¹⁷⁷Lu-Nimotuzumab to EGFR expressed on A549 and A431 cells was confirmed by competitive assay using increasing amounts of unlabeled Nimotuzumab. Cellular responses of A549 (low EGFR) and A431 (high EGFR) in response to different doses of ¹⁷⁷Lu-Nimotuzumab were determined by Viable count assay for cellular viability, cell-cycle analysis by DNA staining, apoptotic assay for cell death, and CFSE dilution assay for cellular proliferation capacity. The number of DNA DSBs formed was determined using γ-H2AX assay with PI staining. Transcription of genes involved in DNA damage response and repair (DRR) pathways was monitored by RT-qPCR.

RESULTS

¹⁷⁷Lu-Nimotuzumab characterized by SE-HPLC exhibited a radiochemical purity of 99.1 ± 0.6%. Cell binding competition studies with ¹⁷⁷Lu-Nimotuzumab showed specific binding of 34.3 ± 1.7% with A431 cells and 18.4 ± 1.9% with A549 cells which decreased when co-incubated with unlabeled Nimotuzumab. Cytotoxicity and DNA damage (DNA DSBs) increased with an increase in the dose of ¹⁷⁷Lu-Nimotuzumab. A549 displayed G2/M arrest while A431 showed G1 arrest. Apoptotic death was determined to be one of the modes of death of arrested A549 and A431 cells which increases with the increase in the dose of ¹⁷⁷Lu-Nimotuzumab. Loss of proliferation capacity was higher in A431 showed by CFSE staining at different doses of ¹⁷⁷Lu-Nimotuzumab. Transcription profile of most DRR genes in A431 and A549 showed a decrease in the transcription at 4 h followed by recovery at 16 h post-treatment. The degree of transcription of most DRR genes was similar, irrespective of ¹⁷⁷Lu-Nimotuzumab dose.

CONCLUSION

¹⁷⁷Lu-Nimotuzumab induces different cellular arrest and molecular responses in low EGFR expressing A549 and high EGFR expressing A431 tumor cells. This study would enable the development of integrative novel treatment strategies for radioimmunotherapy in low and high EGFR expressing tumors by ¹⁷⁷Lu-Nimotuzumab with therapeutic gains.

Harnessing the targeting potential of differential radiobiological effects of photon versus particle radiation for cancer treatment

Radiotherapy is one of the major modalities for malignancy treatment. High linear energy transfer (LET) charged-particle beams, like proton and carbon ions, exhibit favourable depth-dose distributions and radiobiological enhancement over conventional low-LET photon irradiation, thereby marking a new era in high precision medicine. Tumour cells have developed multicomponent signal transduction networks known as DNA damage responses (DDRs), which initiate cell-cycle checkpoints and induce double-strand break (DSB) repairs in the nucleus by nonhomologous end joining or homologous recombination pathways, to manage ionising radiation (IR)-induced DNA lesions. DNA damage induction and DSB repair pathways are reportedly dependent on the quality of radiation delivered. In this review, we summarise various types of DNA lesion and DSB repair mechanisms, upon irradiation with low and high-LET radiation, respectively. We also analyse factors influencing DNA repair efficiency. Inhibition of DNA damage repair pathways and dysfunctional cell-cycle checkpoint sensitises tumour cells to IR. Radio-sensitising agents, including DNA-PK inhibitors, Rad51 inhibitors, PARP inhibitors, ATM/ATR inhibitors, chk1 inhibitors, wee1 kinase inhibitors, Hsp90 inhibitors, and PI3K/AKT/mTOR inhibitors have been found to enhance cell killing by IR through interference with DDRs, cell-cycle arrest, or other cellular processes. The cotreatment of these inhibitors with IR may represent a promising therapeutic strategy for cancer.

The survival benefit of postmastectomy radiotherapy for breast cancer patients with T1-2N1 disease according to molecular subtype

OBJECTIVE

To evaluate the significance of postmastectomy radiotherapy (PMRT) in female breast cancer patients with T1-2N1M0 disease according to molecular subtypes and other risk factors.

METHOD

We conducted a retrospective cohort-based study utilizing the Surveillance, Epidemiology, and End Results database. Patients who were diagnosed with T1-2N1M0 invasive breast cancer and received mastectomy between 2010 and 2014 were enrolled in our study. Overall survival (OS) was calculated with Kaplan-Meier method, and multivariant Cox hazard model was conducted to identify the impact of PMRT according to molecular subtypes and other risk factors. Propensity score matching (PSM) was applied to balance measurable confounders.

RESULTS

Of all the 16,521 enrolled patients, 5775 (35.0%) cases received PMRT. The distribution of molecular subtype is 71.4% for Luminal A, 13.2% for Luminal B, 5.1% for HER2 enriched, and 10.3% for TNBC. The OS was significantly better for patients in PMRT group than the Non-PMRT group (P < 0.0001). Stratified by molecular subtype, PMRT significantly prolonged survival in Luminal A patients (HR: 0.759, 95% CI: 0.651-0.884, P < 0.001), Yet it brought no significant survival advantage in Luminal B, TNBC or HER2 enriched subtype (P = 0.914, P = 0.124, P = 0.103, respectively). Also, PMRT bore prognostic significance among those patients who were older than 56 years old, single, white, exempt from reconstruction and chemotherapy, and were with ductal, GradeⅡtumor (all P < 0.05). After PSM, the survival benefit of PRMT sustained in Luminal A patients with T1 tumor concomitant with one positive lymph node.

CONCLUSION

Our study demonstrates a beneficial impact for PMRT on overall survival among Luminal A subtype breast cancer patients with T1-2N1 disease. The selection of PMRT should be stratified by molecular subtype and other risk factors.

Nimotuzumab for Patients With Inoperable Cancer of the Head and Neck

EGFR activation induces cell proliferation, neoformation of blood vessels, survival, and metastasis of the cancer cells. Nimotuzumab is an engineered, intermediate affinity anti-EGFR antibody, that apart from other drugs in its class, is very safe and does not cause hypomagnesemia or grade 3–4 cutaneous rash. The antibody inhibits cell proliferation and angiogenesis, activates natural killer cells, stimulates dendritic cell maturation, and induces cytotoxic T cells. Nimotuzumab restores MHC-I expression on tumor cells, hindering one of the EGFR immune-escape ways. The antibody has been extensively studied in 7 clinical trials, concurrently with irradiation or irradiation plus chemotherapy in subjects with inoperable head and neck tumors. Nimotuzumab was safe and efficacious in unfit patients receiving irradiation alone and in subjects treated with cisplatin and radiotherapy. In patients with locally advanced squamous cell carcinomas of the head and neck, nimotuzumab in combination with low dose cisplatin and radiotherapy was superior to cisplatin and radiotherapy in progression free survival, disease free survival, and locoregional tumor control.

Identifying Long Non-coding RNA of Prostate Cancer Associated With Radioresponse by Comprehensive Bioinformatics Analysis

Although radiotherapy is greatly successful in the treatment of prostate cancer (PCa), radioresistance is still a major challenge in the treatment. To our knowledge, this study is the first to screen long non-coding RNAs (lncRNAs) associated with radioresponse in PCa by The Cancer Genome Atlas (TCGA). Bioinformatics methods were used to identify the differentially expressed lncRNAs and protein-coding genes (PCGs) between complete response (CR) and non-complete response (non-CR) groups in radiotherapy. Statistical methods were applied to identify the correlation between lncRNAs and radioresponse as well as lncRNAs and PCGs. The correlation between PCGs and radioresponse was analyzed using weighted gene co-expression network analysis (WGCNA). The three online databases were used to predict the potential target miRNAs of lncRNAs and the miRNAs that might regulate PCGs. RT-qPCR was utilized to detect the expression of lncRNAs and PCGs in our PCa patients. A total of 65 differentially expressed lncRNAs and 468 differentially expressed PCGs were found between the two groups of PCa. After the chi-square test, LINC01600 was selected to be highly correlated with radioresponse from the 65 differentially expressed lncRNAs. Pearson correlation analysis found 558 PCGs co-expressed with LINC01600. WGCNA identified the darkred module associated with radioresponse in PCa. After taking the intersection of the darkred module of WGCNA, differentially expressed PCGs between the two groups of PCa, and the PCGs co-expressed with LINC01600, three PCGs, that is, JUND, ZFP36, and ATF3 were identified as the potential target PCGs of LINC01600. More importantly, we detected the expression of LINC01600 and three PCGs using our PCa patients, and finally verified that LINC01600 and JUND were differentially expressed between CR and non-CR groups, excluding ZFP36 and ATF3. Meantime, the potential regulation ability of LINC01600 for JUND in PCa cell lines was initially explored. In addition, we constructed the competing endogenous RNA (ceRNA) network of LINC01600—miRNA—JUND. In conclusion, we initially reveal the association of LINC01600 with radioresponse in PCa and identify its potential target PCGs for further basic and clinical research.

Targeting AKT/PKB to improve treatment outcomes for solid tumors

The serine/threonine kinase AKT, also known as protein kinase B (PKB), is the major substrate to phosphoinositide 3-kinase (PI3K) and consists of three paralogs: AKT1 (PKBα), AKT2 (PKBβ) and AKT3 (PKBγ). The PI3K/AKT pathway is normally activated by binding of ligands to membrane-bound receptor tyrosine kinases (RTKs) as well as downstream to G-protein coupled receptors and integrin-linked kinase. Through multiple downstream substrates, activated AKT controls a wide variety of cellular functions including cell proliferation, survival, metabolism, and angiogenesis in both normal and malignant cells. In human cancers, the PI3K/AKT pathway is most frequently hyperactivated due to mutations and/or overexpression of upstream components. Aberrant expression of RTKs, gain of function mutations in PIK3CA, RAS, PDPK1, and AKT itself, as well as loss of function mutation in AKT phosphatases are genetic lesions that confer hyperactivation of AKT. Activated AKT stimulates DNA repair, e.g. double strand break repair after radiotherapy. Likewise, AKT attenuates chemotherapy-induced apoptosis. These observations suggest that a crucial link exists between AKT and DNA damage. Thus, AKT could be a major predictive marker of conventional cancer therapy, molecularly targeted therapy, and immunotherapy for solid tumors. In this review, we summarize the current understanding by which activated AKT mediates resistance to cancer treatment modalities, i.e. radiotherapy, chemotherapy, and RTK targeted therapy. Next, the effect of AKT on response of tumor cells to RTK targeted strategies will be discussed. Finally, we will provide a brief summary on the clinical trials of AKT inhibitors in combination with radiochemotherapy, RTK targeted therapy, and immunotherapy.

Nimotuzumab with intensity-modulated radiation therapy in unresectable and platinum-ineligible locally advanced head-and-neck cancer

Background:

Outcomes with conventional treatment are poor in patients with squamous cell carcinoma of head and neck (SCCHN). Treatment options are further limited for patients ineligible to receive platinum-based chemotherapy due to various factors such as geriatric age, comorbidity, and organ dysfunctions. The present study retrospectively evaluated the effectiveness of nimotuzumab when added to radiation therapy in unresectable, locally advanced SCCHN patients who were ineligible for platinum-based chemotherapy.

Materials and Methods:

The medical records of 21 patients with unresectable, locally advanced head-and-neck cancer and histologically confirmed squamous cell carcinoma who were ineligible for platinum-based chemotherapy treated with nimotuzumab and intensity-modulated radiation therapy (IMRT) from 2012 to 2017 were retrospectively analyzed. The tumor response rate and overall survival (OS) were analyzed. Patients were assessed for toxicity and adverse events (AEs) as per CTCAE version 4. Statistical analysis was performed using SPSS software.

Results:

The median number of doses of nimotuzumab received was 6, and median dose of radiotherapy was 60 Gy. The tumor response rate was calculated at 24 weeks after the completion of radiotherapy and was as follows: 76.2% (16) of patients showed complete response, 9.5% (2) of patients showed partial response, 4.8% (1) of patients showed stable disease, and 9.5% (2) of patients showed progression of disease. Median OS was 21 months, whereas 1-year survival rate was 63.7%. No Grade 3 or Grade 4 AEs were observed.

Conclusion:

Nimotuzumab with IMRT has achieved promising clinical outcomes in unresectable locally advanced SCCHN patients who are ineligible for platinum-based chemotherapy, without accumulation of toxicity.

The prognosis comparison of different molecular subtypes of breast tumors after radiotherapy and the intrinsic reasons for their distinct radiosensitivity

Radiotherapy can increase the cell cycle arrest that promotes apoptosis, reduces the risk of tumor recurrence and has become an irreplaceable component of systematic treatment for patients with breast cancer. Substantial advances in precise radiotherapy unequivocally indicate that the benefits of radiotherapy vary depending on intrinsic subtypes of the disease; luminal A breast cancer has the highest benefit whereas human epidermal growth factor receptor 2 (HER2)-positive and triple negative breast cancer (TNBC) are affected to a lesser extent irrespective of the selection of radiotherapy strategies, such as conventional whole-breast irradiation (CWBI), accelerated partial-breast irradiation (APBI), and hypofractionated whole-breast irradiation (HWBI). The benefit disparity correlates with the differential invasiveness, malignance, and radiosensitivity of the subtypes. A combination of a number of molecular mechanisms leads to the strong radioresistant profile of HER2-positive breast cancer, and sensitization to irradiation can be induced by multiple drugs or compounds in luminal disease and TNBC. In this review, we aimed to summarize the prognostic differences between various subtypes of breast tumors after CWBI, APBI, and HWBI, the potential reasons for drug-enhanced radiosensitivity in luminal breast tumors and TNBC, and the robust radioresistance of HER2-positive cancer.

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Retrospective study comparing anti-EGFR monoclonal antibody plus cisplatin-based chemoradiotherapy versus chemoradiotherapy alone for stage II-IVb nasopharyngeal carcinoma and prognostic value of EGFR and VEGF expression

OBJECTIVES

The benefits of adding anti-EGFR therapy to conventional chemoradiotherapy (CRT) for nasopharyngeal carcinoma (NPC) remain uncertain, possibly because only a subgroup of patients show better outcome. To address this issue, we compared the efficacy of CRT plus cetuximab (CTX) or nimotuzumab (NTZ) to CRT alone for stage II-IVb NPC and examined possible prognostic indicators, including tumour EGFR and VEGR expression levels.

DESIGN, SETTING AND PARTICIPANTS

This retrospective study enrolled 1812 patients at initial NPC diagnosis at Nanfang Hospital Affiliated to Southern Medical University between January 2005 and December 2015. The cetuximab or nimotuzumab plus CRT group (CRT+NTZ/CTX) and the conventional chemoradiotherapy group (CRT) were matched by propensity scoring at 1:5, yielding 282 patients at clinical stage II-IVb with 47 in the CRT+NTZ/CTX group and 235 in the CRT group.

MAIN OUTCOME MEASURES

The endpoints of the present study were locoregional relapse-free survival (LRFS), distant metastasis-free survival (DMFS), overall survival (OS). Immunohistochemistry (IHC) was used to investigate EGFR and VEGF expression levels in 31 patients of the CRT+NTZ/CTX group.

RESULTS

There were no significant differences in LRFS, DMFS and OS, haematologic toxicity reactions, and gastrointestinal reactions between CRT+NTZ/CTX and CRT groups. There was a positive correlation between EGFR and VEGF expression levels. Among CRT+NTZ/CTX patients, those with high EGFR and VEGF expression levels exhibited better DMFS.

CONCLUSIONS

Addition of anti-EGFR to cisplatin-based CRT appears to benefit only a subset of stage II-IVb NPC patients, those with elevated EGFR and VEGF expression levels.

Safety and efficacy of nimotuzumab with concurrent chemoradiotherapy in unresectable locally advanced squamous cell carcinoma of head and neck: An Indian rural hospital experience

Context:

Nimotuzumab is the only anti-epidermal growth factor receptor monoclonal antibody which can be safely added to concurrent chemoradiotherapy (CRT) to improve efficacy in the management of unresectable, locally advanced squamous cell carcinoma of head and neck (LA-SCCHN). However, the evidence available on this is limited.

Aims:

We retrospectively investigated efficacy and safety of nimotuzumab when combined with chemoradiation for LA-SCCHN.

Settings and Design:

Hospital records of 39 patients from January 2012 to December 2016 diagnosed with locally advanced (Stage III-IVb), unresectable SCCHN, and treated with concurrent CRT with weekly nimotuzumab were reviewed retrospectively after fulfilling the inclusion/exclusion criteria.

Subjects and Methods:

Tumor response was calculated as per response evaluation criteria in solid tumors criteria 1.1. Association of tumor response with independent variables was assessed. Overall survival (OS) and progression-free survival (PFS) were calculated. All patients were assessed for toxicity as per common terminology criteria for adverse events Common Terminology Criteria for Adverse Events v 4.0 (U.S. Department of health and human services, National Institutes of Health, National Cancer Institute).

Results:

At 6 months after completion of treatment, objective response rate was 97.44% with 26 (66.67%) patients attaining Complete response (CR), 12 (30.77%) patients with Partial response (PR), and one patient (2.56%) had stable disease. Subgroup analysis did not show a significant association of tumor response with independent factors. OS at 1 and 2-year was 100% and 72.9%, while PFS at 1 and 2-year was 87% and 54.40%. The incidence of Grade I, II, III, and IV toxicity was 30%, 18.18%, 41.82%, and 10%, respectively. No grade V toxicity was observed. Common adverse events observed were mucositis (33.64%), skin reaction (24.55%), neutropenia (20.91%), vomiting (18.18%), and diarrhea (2.73%).

Conclusions:

Nimotuzumab is an efficacious and safe option when added to concurrent CRT in unresectable, LA-SCCHN.

Akt and mTORC1 signaling as predictive biomarkers for the EGFR antibody nimotuzumab in glioblastoma

Glioblastoma (GB) is the most frequent primary brain tumor in adults with a dismal prognosis despite aggressive treatment including surgical resection, radiotherapy and chemotherapy with the alkylating agent temozolomide. Thus far, the successful implementation of the concept of targeted therapy where a drug targets a selective alteration in cancer cells was mainly limited to model diseases with identified genetic drivers. One of the most commonly altered oncogenic drivers of GB and therefore plausible therapeutic target is the epidermal growth factor receptor (EGFR). Trials targeting this signaling cascade, however, have been negative, including the phase III OSAG 101-BSA-05 trial. This highlights the need for further patient selection to identify subgroups of GB with true EGFR-dependency. In this retrospective analysis of treatment-naïve samples of the OSAG 101-BSA-05 trial cohort, we identify the EGFR signaling activity markers phosphorylated PRAS40 and phosphorylated ribosomal protein S6 as predictive markers for treatment efficacy of the EGFR-blocking antibody nimotuzumab in MGMT promoter unmethylated GBs. Considering the total trial population irrespective of MGMT status, a clear trend towards a survival benefit from nimotuzumab was already detectable when tumors had above median levels of phosphorylated ribosomal protein S6. These results could constitute a basis for further investigations of nimotuzumab or other EGFR- and downstream signaling inhibitors in selected patient cohorts using the reported criteria as candidate predictive biomarkers.

Long non-coding RNA PVT1 predicts poor prognosis and induces radioresistance by regulating DNA repair and cell apoptosis in nasopharyngeal carcinoma

The long non-coding RNA, plasmacytoma variant translocation 1 (PVT1), is highly expressed in a variety of tumors, and is believed to be a potential oncogene. However, the role and mechanism of action of PVT1 in the carcinogenesis and progression of nasopharyngeal carcinomas (NPCs) remains unclear. In this study, for the first time, we have discovered that PVT1 shows higher expression in NPCs than in normal nasopharyngeal epithelial tissue, and patients with NPCs who show higher expression of PVT1 have worse progression-free and overall survivals. Additionally, we observed that the proliferation of NPC cells decreased, and their rate of apoptosis increased; these results indicated that the knockdown of PVT1 expression in the NPC cells induced radiosensitivity. Further, we have shown that the knockdown of PVT1 expression can induce apoptosis in the NPC cells by influencing the DNA damage repair pathway after radiotherapy. In general, our study shows that PVT1 may be a novel biomarker for prognosis and a new target for the treatment of NPCs. Additionally, targeting PVT1 may be a potential strategy for the clinical management of NPC and for the improvement of the curative effect of radiation in NPCs.

The impact of autophagy on cell death modalities in CRL-5876 lung adenocarcinoma cells after their exposure to γ-rays and/or erlotinib

In most patients with lung cancer radiation treatment is used either as single agent or in combination with radiosensitizing drugs. However, the mechanisms underlying combined therapy and its impact on different modes of cell death have not yet been fully elucidated. We aimed to examine effects of single and combined treatments with γ-rays and erlotinib on radioresistant CRL-5876 human lung adenocarcinoma cells with particular emphasis on cell death. CRL-5876 cells were treated with γ-rays and/or erlotinib and changes in cell cycle, DNA repair dynamics, ultrastructure, nuclear morphology and protein expression were monitored at different time points. To reveal the relationship between types of cell death that arise after these treatments, autophagy was blocked with chloroquine. We found that higher dose of γ-rays causes G2/M arrest while adding of erlotinib to this treatment decreases the number of cells in S phase. Impact of erlotinib on kinetics of disappearance of irradiation-induced DNA double strand breaks is reflected in the increase of residual γ-H2AX foci after 24 h. γ-rays provoke cytoprotective autophagy which precedes development of senescence. Erlotinib predominantly induces apoptosis and enlarges the number of apoptotic cells in the irradiated CRL-5876 cells. Chloroquine improved cytotoxicity induced by radiation and erlotinib, increased apoptosis and decreased senescence in the CRL-5876 cells. The results obtained on CRL-5876 cells indicate significant radiosensitizing effect of erlotinib and suggest that chloroquine in the combination with the above treatments may have an additional antitumor effect in lung adenocarcinoma.

IGF-1 from adipose-derived mesenchymal stem cells promotes radioresistance of breast cancer cells

PURPOSE

The aim of this study was to investigate effects of adipose-derived mesenchymal stem cells (AMSCs) on radioresistance of breast cancer cells.

MATERIALS AND METHODS

MTT assays were used to detect any influence of AMSC supernatants on proliferation of breast cancer cells; cell migration assays were used to determine the effect of breast cancer cells on the recruitment of AMSCs; the cell survival fraction post-irradiation was assessed by clonogenic survival assay; γ-H2AX foci number post-irradiation was determined via fluorescence microscopy; and expression of IGF-1R was detected by Western blotting.

RESULTS

AMSC supernatants promoted proliferation and radioresistance of breast cancer cells. Breast cancer cells could recruit AMSCs, especially after irradiation. IGF-1 derived from AMSCs might be responsible for the radioresistance of breast cancer cells.

CONCLUSIONS

Our results suggest that AMSCs in the tumor microenvironment may affect the outcome of radiotherapy for breast cancer in vitro.

A comparison of the biological effects of 125I seeds continuous low-dose-rate radiation and 60Co high-dose-rate gamma radiation on non-small cell lung cancer cells

Objectives

To compare the biological effects of ¹²⁵I seeds continuous low-dose-rate (CLDR) radiation and ⁶⁰Co γ-ray high-dose-rate (HDR) radiation on non-small cell lung cancer (NSCLC) cells.

Materials and Methods

A549, H1299 and BEAS-2B cells were exposed to ¹²⁵I seeds CLDR radiation or ⁶⁰Co γ-ray HDR radiation. The survival fraction was determined using a colony-forming assay. The cell cycle progression and apoptosis were detected by flow cytometry (FCM). The expression of the apoptosis-related proteins caspase-3, cleaved-caspase-3, PARP, cleaved-PARP, BAX and Bcl-2 were detected by western blot assay.

Results

After irradiation with ¹²⁵I seeds CLDR radiation, there was a lower survival fraction, more pronounced cell cycle arrest (G₁ arrest and G₂/M arrest in A549 and H1299 cells, respectively) and a higher apoptotic ratio for A549 and H1299 cells than after ⁶⁰Co γ-ray HDR radiation. Moreover, western blot assays revealed that ¹²⁵I seeds CLDR radiation remarkably up-regulated the expression of Bax, cleaved-caspase-3 and cleaved-PARP proteins and down-regulated the expression of Bcl-2 proteins in A549 and H1299 cells compared with ⁶⁰Co γ-ray HDR radiation. However, there was little change in the apoptotic ratio and expression of apoptosis-related proteins in normal BEAS-2B cells receiving the same treatment.

Conclusions

¹²⁵I seeds CLDR radiation led to remarkable growth inhibition of A549 and H1299 cells compared with ⁶⁰Co HDR γ-ray radiation; A549 cells were the most sensitive to radiation, followed by H1299 cells. In contrast, normal BEAS-2B cells were relatively radio-resistant. The imbalance of the Bcl-2/Bax ratio and the activation of caspase-3 and PARP proteins might play a key role in the anti-proliferative effects induced by ¹²⁵I seeds CLDR radiation, although other possibilities have not been excluded and will be investigated in future studies.

Nimotuzumab enhances radiation sensitivity of NSCLC H292 cells in vitro by blocking epidermal growth factor receptor nuclear translocation and inhibiting radiation-induced DNA damage repair

Background

The epidermal growth factor receptor (EGFR) signaling pathway plays a significant role in radiation resistance. There is evidence that EGFR nuclear translocation is associated with DNA double-strand breaks (DSB) repair. Nimotuzumab has shown the effect of radiosensitization in various cancer cells, but little is known about the relationship between nimotuzumab and EGFR nuclear translocation in non-small cell lung cancer (NSCLC) cell lines. In this study, we selected two NSCLC cell lines, namely, H292 (with high EGFR expression) and H1975 (with low EGFR expression) and explored the mechanisms underlying radiation sensitivity.

Methods

MTT assay, clonogenic survival assay, and flow cytometry were performed separately to test cell viability, radiation sensitivity, cell cycle distribution, and apoptosis. Protein γ-H2AX, DNA-PK/p-DNA-PK, and EGFR/p-EGFR expression were further compared both in the cytoplasm and the nucleus with the western blot.

Results

Nimotuzumab reduced the viability of H292 cells and sensitized H292 cells to ionizing radiation. The radiation sensitivity enhancement ratio (SER) was 1.304 and 1.092 for H292 and H1975 cells, respectively. H292 cells after nimotuzumab administration were arrested at the G0/G1 phase in response to radiation. Apoptosis was without statistical significance in both cell lines. γ-H2AX formation in the combination group (nimotuzumab and radiation) increased both in the cytoplasm and the nucleus along with the decreased expression of nuclear EGFR/p-EGFR and p-DNA-PK in H292 cells (P<0.05) that was more significant than that in H1975 cells.

Conclusion

Our research revealed a possible mechanism to explain the radiosensitivity in H292 cells. Nimotuzumab decreased the radiation-induced activation of DNA-PK by blocking EGFR nuclear translocation and impairing DNA DSB repair, thus enhancing radiosensitivity in H292 cells. Because these results represent early research, the matters of how γ-H2AX and DNA-PK dynamically change simultaneously with nuclear EGFR and the best time to administer nimotuzumab will require further exploration.

Combined treatment of Nimotuzumab and rapamycin is effective against temozolomide-resistant human gliomas regardless of the EGFR mutation status

Background

The treatment of glioblastoma multiforme (GBM) is an unmet clinical need. The 5-year survival rate of patients with GBM is less than 3%. Temozolomide (TMZ) remains the standard first-line treatment regimen for gliomas despite the fact that more than 90% of recurrent gliomas do not respond to TMZ after repeated exposure. We have also independently shown that many of the Asian-derived glioma cell lines and primary cells derived from Singaporean high-grade glioma patients are indeed resistant to TMZ. This issue highlights the need to develop new effective anti-cancer treatment strategies. In a recent study, wild-type epidermal growth factor receptor (wtEGFR) has been shown to phosphorylate a truncated EGFR (known as EGFRvIII), leading to the phosphorylation of STAT proteins and progression in gliomagenesis. Despite the fact that combination of EGFR targeting drugs and rapamycin has been used before, the effect of mono-treatment of Nimotuzumab, rapamycin and combination therapy in human glioma expressing different types of EGFR is not well-studied. Herein, we evaluated the efficacy of dual blockage using monoclonal antibody against EGFR (Nimotuzumab) and an mTOR inhibitor (rapamycin) in Caucasian patient-derived human glioma cell lines, Asian patient-derived human glioma cell lines, primary glioma cells derived from the Mayo GBM xenografts, and primary short-term glioma culture derived from high-grade glioma patients.

Methods

The combination effect of Nimotuzumab and rapamycin was examined in a series of primary human glioma cell lines and glioma cell lines. The cell viability was compared to TMZ treatment alone. Endogenous expressions of EGFR in various GBM cells were determined by western blotting.

Results

The results showed that combination of Nimotuzumab with rapamycin significantly enhanced the therapeutic efficacy of human glioma cells compared to single treatment. More importantly, many of the Asian patient-derived glioma cell lines and primary cells derived from Singaporean high-grade gliomas, which showed resistance to TMZ, were susceptible to the combined treatments.

Conclusions

In conclusion, our results strongly suggest that combination usage of Nimotuzumab and rapamycin exert higher cytotoxic activities than TMZ. Our data suggest that this combination may provide an alternative treatment for TMZ-resistant gliomas regardless of the EGFR status.

LRIG1 enhances the radiosensitivity of radioresistant human glioblastoma U251 cells via attenuation of the EGFR/Akt signaling pathway

The radiotherapy as a local and regional modality is widely applied in treatment of glioma, but most glioblastomas are commonly resistant to irradiation treatment. It remains challengeable to seek out efficient strategies to conquer the resistance of human glioblastoma cells to radiotherapy. Leucine-rich repeats and immunoglobulin-like domains protein 1 (LRIG1) is a newly discovered tumor suppressor which involved in regulation of chemosensitivity in various human cancer cells. In the present study, we established a radioresistant U251 cell line (U251R) to investigate the role of LRIG1 in regulation of radiosensitivity in human glioblastoma cells. Significantly decreased expression level of LRIG1 and enhanced expression of EGFR and phosphorylated Akt were detected in U251R cells compared with the parental U251 cells. U251R cells exhibited an advantage in colony formation ability, which accompanied by remarkably reduced X-ray-induced γ-H2AX foci formation and cell apoptosis. LRIG1 overexpression significantly inhibited the colony formation ability of U251R cells and obviously enhanced X-ray-inducedγ-H2AX foci formation and cell apoptosis. In addition, up-regulated expression of LRIG1 suppressed the expression level of EGFR and phosphorylated Akt protein. Our results demonstrated that LRIG1 expression was related to the radiosensitivity of human glioblastoma cells and may play an important role in the regulation of cellular radiosensitivity of human glioblastoma cells through the EGFR/Akt signaling pathway.

Therapeutic integration of new molecule-targeted therapies with radiotherapy in lung cancer

Lung cancer is the most common form of the disease and the leading cause of cancer deaths worldwide. Non-small-cell lung cancer (NSCLC) accounts for approximately 80-85% of all lung cancers. Forty percent of all cases present with stage III, and many of them are considered inoperable (staged IIIA with mediastinal lymph node involvement) or stage IIIB disease. Concurrent platinum-based chemotherapy and thoracic radiation has demonstrated survival benefits in these patients. We review the role of new target agents in combination with radiotherapy in stage III NSCLC. Antiangiogenics improve tumor oxygenation thereby improving the therapeutic efficacy of irradiation in models. Bevacizumab in combination with thoracic radiation has shown high toxicity. However, other antiangiogenic agents are more promising. Radiation activates epidermal growth factor receptor (EGFR) pathways, inducing radioresistance, cell proliferation and enhanced DNA repair. After promising data from preclinical models and early clinical trials, cetuximab did not show any benefit in a recent phase III trial. Panitumumab and nimotuzumab are under evaluation. Gefitinib has been investigated in combination with radiotherapy for unresectable stage III NSCLC, but results in maintenance treatment after chemoradiotherapy were not encouraging. Erlotinib has also been tested in a phase II trial with chemoradiotherapy. Other new pathways and agents are being studied, such as m-TOR pathway, bortezomib, heat shock protein 90 (Hsp90) inhibition, histone deacetylase inhibitors (HDACS), aurora kinases, mitogen activated protein kinases (MARK) and PARP inhibitors.

DNA-dependent protein kinase catalytic subunit inhibitor reverses acquired radioresistance in lung adenocarcinoma by suppressing DNA repair

The mechanisms underlying lung cancer radioresistance remain to be fully elucidated. The DNA repair pathway is a predominant target of radiotherapy, which is considered to be involved in the acquired radioresistance of cancer cells. The present study aimed to establish a radioresistant cell model using the A549 human lung cancer cell line, and to further investigate the potential mechanisms underlying the radioresistance. The A549R radioresistant lung cancer cell variant was established by exposing the parental A549 cells to repeated γ-ray irradiation at a total dose of 60 Gy. Colony formation assays were then used to determine cell survival following γ-ray exposure. The established radioresistant cells were subsequently treated with or without the NU7026 DNA-PKcs inhibitor. The levels of DNA damage were determined by counting the number of fluorescent γ-H2AX foci in the cells. The cellular capacity for DNA repair was assessed using antibodies for the detection of various DNA repair pathway proteins. The radioresistant sub-clones exhibited significantly decreased survival following NU7026 treatment, compared with the parental cells, as determined by colony formation assays (P<0.05), and this finding was found to be dose-dependent. Treatment with the DNA-dependent protein kinase (DNA-PK) inhibitor significantly reduced γ-H2AX foci formation (P<0.05) following acute radiation exposure in the radioresistant sub-clones, compared with the parental control cells. The decreased levels of γ-H2AX were accompanied by an increase in the percentage of apoptotic cells in the radioresistant cell line following post-radiation treatment with the DNA-PKcs inhibitor. The expression levels of proteins associated with the DNA repair pathway were altered markedly in the cells treated with NU7026. The results of the present study suggested that radioresistance may be associated with enhanced DNA repair following exposure to radiation, resulting in reduced apoptosis. Therefore, the quantity of γ-H2AX determines the radioresistance of cells. The DNA repair pathway is important in mediating radioresistance, and treatment with the DNA-PKcs inhibitor, NU7026 restored the acquired radiation resistance.

[Nimotuzumab significantly enhances chemosensitivity of PC9 human lung adenocarcinoma cells to paclitaxel in vitro]

BACKGROUND

Nimotuzumab is a humanized IgG1 type monoclonal antibody targeting epidermal growth factor receptor, and can enhance chemosensitivity and radiosensitivity of certain cancers. The aim of this study is to investigate the effects of nimotuzumab on the chemosensitivities of PC9 human lung adenocarcinoma cells to common chemtherapeutic drugs including ciaplatin, gemcitabine, paclitaxel, pemetrexed and vinorelbine, and to elucidate possible mechanisms.

METHODS

PC9 human lung adenocarcinoma cell line was used in the study. Cell proliferation was determined by WST-1 assay and cell apoptosis was detected by TUNEL assay. Cell cycle distribution was analyzed by DNA analysis with FACS. Tublin and microfilaments were observed by immunofluorescence staining.

RESULTS

Nimotuzumab significantly enhanced the chemosensitivity of PC9 cells to paclitaxel. Cell proliferation was inhibited significantly (P<0.05) and cell apoptosis rate was higher in nimotuzumab combined with low dose paclitaxel (0.05 μg/mL) group (P=0.013). G2/M arrest was increased significantly by nimotuzumab combined with paclitaxel group (P<0.05). Nimotuzumab caused aggregation of tublin and microfilaments into well organized microtubules.

CONCLUSIONS

Nimotuzumab enhanced the chemosensitivity of PC9 cell to paclitaxel by enhancing G2/M arrest and aggregation of tublin and microfilaments. Therefore, Nimotuzumab combined with taxane drugs could be a potential effective regimen in non-small cell lung cancer.

Icotinib hydrochloride enhances the effect of radiotherapy by affecting DNA repair in colorectal cancer cells

The aim of the present study was to explore the efficacy and mechanism of the radiosensitisation of icotinib hydrochloride (IH), a novel oral epidermal growth factor receptor-tyrosine kinase activity inhibitor, by evaluating the changes in tumour cell double-strand breaks (DSBs) repair, cell cycle and apoptosis following a combination of IH and radiotherapy (RT) in human colorectal adenocarcinoma cell lines. The HT29 and HCT116 human CRC cell lines were treated with IH and/or radiation. Effects on cell viability and cell cycle progression were measured by MTT, a clonogenic survival assay, and flow cytometry. Immunofluorescent staining and western blot analysis were applied to detect the expression of γ-H2AX and 53BP1 in the different treatment groups. Finally, the in vivo effect on the growth of CRC xenografts was assessed in athymic nude mice. IH inhibited the proliferation and enhanced the radiosensitivity in HT29 and HCT116 CRC cells lines. IH combined with radiation increased cell cycle arrest in the G2/M phase compared to the other treatments in the HT29 cell line (P<0.05). Similarly, cell cycle arrest occurred in the HCT116 cell line, although this increase did not result in significant differences in the RT group (P>0.05). IH combined with radiation significantly inhibited the expression of γ-H2AX and 53BP1 based on results of immunofluorescent staining and western blot analysis. In vivo, IH plus radiation significantly inhibited the tumour growth compared to either agent independently. In conclusion, IH significantly increased the radiosensitivity of HT29 and HCT116 cells in vitro and in vivo. Radiation combined with EGFR blockade inhibited tumour proliferation, increased apoptosis, prolonged G2/M arrest and significantly enhanced DNA injury in colorectal cancer. These data support the clinical trials of biologically targeted and conventional therapies in the treatment of cancer.

Roles of glucose transporter-1 and the phosphatidylinositol 3‑kinase/protein kinase B pathway in cancer radioresistance (review)

The mechanisms underlying cancer radioresistance remain unclear. Several studies have found that increased glucose transporter‑1 (GLUT‑1) expression is associated with radioresistance. Recently, the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) pathway was reported to be involved in the control of GLUT‑1 trafficking and activity. Activation of the PI3K/Akt pathway may itself be associated with cancer radioresistance. Thus, increasing attention has been devoted to the effects of modifying the expression of GLUT‑1 and the PI3K/Akt pathway on the increase in the radiosensitivity of cancer cells. This review discusses the importance of the association between elevated expression of GLUT‑1 and activation of the PI3K/Akt pathway in the development of radioresistance in cancer.

EGFR modulates DNA synthesis and repair through Tyr phosphorylation of histone H4

Posttranslational modifications of histones play fundamental roles in many biological functions. Specifically, histone H4-K20 methylation is critical for DNA synthesis and repair. However, little is known about how these functions are regulated by the upstream stimuli. Here, we identify a tyrosine phosphorylation site at Y72 of histone H4, which facilitates recruitment of histone methyltransferases (HMTases), SET8 and SUV4-20H, to enhance its K20 methylation, thereby promoting DNA synthesis and repair. Phosphorylation-defective histone H4 mutant is deficient in K20 methylation, leading to reduced DNA synthesis, delayed cell cycle progression, and decreased DNA repair ability. Disrupting the interaction between epidermal growth factor receptor (EGFR) and histone H4 by Y72 peptide significantly reduced tumor growth. Furthermore, EGFR expression clinically correlates with histone H4-Y72 phosphorylation, H4-K20 monomethylation, and the Ki-67 proliferation marker. These findings uncover a mechanism by which EGFR transduces signal to chromatin to regulate DNA synthesis and repair.

Radiation oncology in vitro: trends to improve radiotherapy through molecular targets

Much has been investigated to improve the beneficial effects of radiotherapy especially in that case where radioresistant behavior is observed. Beyond simple identification of resistant phenotype the discovery and development of specific molecular targets have demonstrated therapeutic potential in cancer treatment including radiotherapy. Alterations on transduction signaling pathway related with MAPK cascade are the main axis in cancer cellular proliferation even as cell migration and invasiveness in irradiated tumor cell lines; then, for that reason, more studies are in course focusing on, among others, DNA damage enhancement, apoptosis stimulation, and growth factors receptor blockages, showing promising in vitro results highlighting molecular targets associated with ionizing radiation as a new radiotherapy strategy to improve clinical outcome. In this review we discuss some of the main molecular targets related with tumor cell proliferation and migration as well as their potential contributions to radiation oncology improvements.

Sensitisation of human lung adenocarcinoma A549 cells to radiotherapy by Nimotuzumab is associated with enhanced apoptosis and cell cycle arrest in the G2/M phase

The epidermal growth factor receptor (EGFR) plays an important role in tumorigenesis and maintenance of cancers, making it a possible therapeutic target for cancer treatment. Nimotuzumab (h-R3), a humanised monoclonal antibody against EGFR, sensitises human lung adenocarcinoma A549 cells to radiotherapy. We have investigated the underlying molecular mechanism by treating A549 cells with Nimotuzumab (100 μg/mL) alone or in combination with a single dose of 2 Gy irradiation, and analysing apoptosis and cell cycle distribution by flow cytometry. Nimotuzumab significantly enhanced radiation-induced apoptosis of A549 cells as evidenced by increased cell apoptosis (7.15 ± 0.30%) compared with the control group (1.08 ± 0.25%), Nimotuzumab alone group (4.89 ± 0.30%) and irradiation alone group (5.90 ± 0.15%). Combining Nimotuzumab with irradiation significantly arrested cells in the G2/M phase (43. ± 0.36%) compared radiotherapy alone (18.7 ± 0.35%) and single Nimotuzumab treatment (27.2 ± 0.17%). A combination of Nimotuzumab with radiation increased apoptosis and G2/M phase arrest in human lung adenocarcinoma A549 cells, suggesting potential development of combinatorial therapy of Nimotuzumab with radiotherapy for lung cancer.