Radioresistant head and neck squamous cell carcinoma cells: intracellular signaling, putative biomarkers for tumor recurrences and possible therapeutic targets

CD133 expression is associated with less DNA repair, better response to chemotherapy and survival in ER-positive/HER2-negative breast cancer

PURPOSE

CD133, a cancer stem cells (CSC) marker, has been reported to be associated with treatment resistance and worse survival in triple-negative breast cancer (BC). However, the clinical relevance of CD133 expression in ER-positive/HER2-negative (ER + /HER2-) BC, the most abundant subtype, remains unknown.

METHODS

The BC cohorts from the Molecular Taxonomy of Breast Cancer International Consortium (METABRIC, n = 1904) and The Cancer Genome Atlas (TCGA, n = 1065) were used to obtain biological variables and gene expression data.

RESULTS

Epithelial cells were the exclusive source of CD133 gene expression in a bulk BC. CD133-high ER + /HER2- BC was associated with CD24, NOTCH1, DLL1, and ALDH1A1 gene expressions, as well as with WNT/β-Catenin, Hedgehog, and Notch signaling pathways, all characteristic for CSC. Consistent with a CSC phenotype, CD133-low BC was enriched with gene sets related to cell proliferation, such as G2M Checkpoint, MYC Targets V1, E2F Targets, and Ki67 gene expression. CD133-low BC was also linked with enrichment of genes related to DNA repair, such as BRCA1, E2F1, E2F4, CDK1/2. On the other hand, CD133-high tumors had proinflammatory microenvironment, higher activity of immune cells, and higher expression of genes related to inflammation and immune response. Finally, CD133-high tumors had better pathological complete response after neoadjuvant chemotherapy in GSE25066 cohort and better disease-free survival and overall survival in both TCGA and METABRIC cohorts.

CONCLUSION

CD133-high ER + /HER2- BC was associated with CSC phenotype such as less cell proliferation and DNA repair, but also with enhanced inflammation, better response to neoadjuvant chemotherapy and better prognosis.

CD133 expression is associated with less DNA repair, better response to chemotherapy and survival in ER-positive/HER2-negative breast cancer

Purpose

CD133, a cancer stem cells (CSC) marker, has been reported to be associated with treatment resistance and worse survival in triple-negative breast cancer (BC). However, the clinical relevance of CD133 expression in ER-positive/HER2-negative (ER+/HER2-) BC, the most abundant subtype, remains unknown.

Methods

The BC cohorts from the Molecular Taxonomy of Breast Cancer International Consortium (METABRIC, n = 1904) and The Cancer Genome Atlas (TCGA, n = 1065) were used to obtain biological variables and gene expression data.

Results

Epithelial cells were the exclusive source of CD133 gene expression in a bulk BC. CD133-high ER+/HER2- BC was associated with CD24, NOTCH1, DLL1, and ALDH1A1 gene expressions, as well as with WNT/β-Catenin, Hedgehog, and Notchsignaling pathways, all characteristic for CSC. Consistent with a CSC phenotype, CD133-low BC was enriched with gene sets related to cell proliferation, such as G2M Checkpoint, MYC Targets V1, E2F Targets, and Ki67 gene expression. CD133-low BC was also linked with enrichment of genes related to DNA repair, such as BRCA1, E2F1, E2F4, CDK1/2. On the other hand, CD133-high tumors had proinflammatory microenvironment, higher activity of immune cells, and higher expression of genes related to inflammation and immune response. Finally, CD133-high tumors had better pathological complete response after neoadjuvant chemotherapy in GSE25066 cohort and better disease-free survival and overall survival in both TCGA and METABRIC cohorts.

Conclusion

CD133-high ER+/HER2- BC was associated with CSC phenotype such as less cell proliferation and DNA repair, but also with enhanced inflammation, better response to neoadjuvant chemotherapy and better prognosis.

The Various Roles of PEDF in Cancer

Pigment epithelium-derived factor (PEDF) is a natural immunomodulator, anti-inflammatory, anti-angiogenic, anti-tumour growth and anti-metastasis factor, which can enhance tumour response to PEDF but can also conversely have pro-cancerous effects. Inflammation is a major cause of cancer, and it has been proven that PEDF has anti-inflammatory properties. PEDF's functional activity can be investigated through measuring metastatic and metabolic biomarkers that will be discussed in this review.

The development of radioresistant oral squamous carcinoma cell lines and identification of radiotherapy-related biomarkers

BACKGROUND

In the treatment of oral squamous cell carcinoma (OSCC), radiation resistance remains an important obstacle to patient outcomes. Progress in understanding the molecular mechanisms of radioresistance has been limited by research models that do not fully recapitulate the biological features of solid tumors. In this study, we aimed to develop novel in vitro models to investigate the underlying basis of radioresistance in OSCC and to identify novel biomarkers.

METHODS

Parental OSCC cells (SCC9 and CAL27) were repeatedly exposed to ionizing radiation to develop isogenic radioresistant cell lines. We characterized the phenotypic differences between the parental and radioresistant cell lines. RNA sequencing was used to identify differentially expressed genes (DEGs), and bioinformatics analysis identified candidate molecules that may be related to OSCC radiotherapy.

RESULTS

Two isogenic radioresistant cell lines for OSCC were successfully established. The radioresistant cells displayed a radioresistant phenotype when compared to the parental cells. Two hundred and sixty DEGs were co-expressed in SCC9-RR and CAL27-RR, and thirty-eight DEGs were upregulated or downregulated in both cell lines. The associations between the overall survival (OS) of OSCC patients and the identified genes were analyzed using data from the Cancer Genome Atlas (TCGA) database. A total of six candidate genes (KCNJ2, CLEC18C, P3H3, PIK3R3, SERPINE1, and TMC8) were closely associated with prognosis.

CONCLUSION

This study demonstrated the utility of constructing isogenic cell models to investigate the molecular changes associated with radioresistance. Six genes were identified based on the data from the radioresistant cells that may be potential targets in the treatment of OSCC.

Tuning between Nuclear Organization and Functionality in Health and Disease

The organization of eukaryotic genome in the nucleus, a double-membraned organelle separated from the cytoplasm, is highly complex and dynamic. The functional architecture of the nucleus is confined by the layers of internal and cytoplasmic elements, including chromatin organization, nuclear envelope associated proteome and transport, nuclear-cytoskeletal contacts, and the mechano-regulatory signaling cascades. The size and morphology of the nucleus could impose a significant impact on nuclear mechanics, chromatin organization, gene expression, cell functionality and disease development. The maintenance of nuclear organization during genetic or physical perturbation is crucial for the viability and lifespan of the cell. Abnormal nuclear envelope morphologies, such as invagination and blebbing, have functional implications in several human disorders, including cancer, accelerated aging, thyroid disorders, and different types of neuro-muscular diseases. Despite the evident interplay between nuclear structure and nuclear function, our knowledge about the underlying molecular mechanisms for regulation of nuclear morphology and cell functionality during health and illness is rather poor. This review highlights the essential nuclear, cellular, and extracellular components that govern the organization of nuclei and functional consequences associated with nuclear morphometric aberrations. Finally, we discuss the recent developments with diagnostic and therapeutic implications targeting nuclear morphology in health and disease.

Erk1/2-Dependent HNSCC Cell Susceptibility to Erastin-Induced Ferroptosis

Unfavorable clinical outcomes mean that cancer researchers must attempt to develop novel therapeutic strategies to overcome therapeutic resistance in patients with HNSCC. Recently, ferroptosis was shown to be a promising pathway possessing druggable targets, such as xCT (SLC7A11). Unfortunately, little is known about the molecular mechanisms underlying the susceptibility of HNSCC cells to ferroptosis. The goal of this study was to determine whether HNSCC cells with activated Erk1/2 are vulnerable to ferroptosis induction. Our results have shown that xCT (SLC7A11) was overexpressed in malignant tissues obtained from the patients with HNSCC, whereas normal mucosa demonstrated weak expression of the protein. In order to investigate the role of Erk1/2 in the decrease in cell viability caused by erastin, xCT-overexpressing FaDu and SCC25 HNSCC cells were used. The ravoxertinib-dependent inhibition of Erk1/2 signaling led to the decrease in erastin efficacy due to the effect on ROS production and the upregulation of ROS scavengers SOD1 and SOD2, resulting in repressed lipid peroxidation. Therefore, it was concluded that the erastin-dependent activation of ferroptosis seems to be a promising approach which can be further developed as an additional strategy for the treatment of HNSCC. As ferroptosis induction via erastin is strongly dependent on the expression of Erk1/2, this MAP kinase can be considered as a predictor for cancer cells' response to erastin.

Reshaping the systemic tumor immune environment (STIE) and tumor immune microenvironment (TIME) to enhance immunotherapy efficacy in solid tumors

The development of combination immunotherapy based on the mediation of regulatory mechanisms of the tumor immune microenvironment (TIME) is promising. However, a deep understanding of tumor immunology must involve the systemic tumor immune environment (STIE) which was merely illustrated previously. Here, we aim to review recent advances in single-cell transcriptomics and spatial transcriptomics for the studies of STIE, TIME, and their interactions, which may reveal heterogeneity in immunotherapy responses as well as the dynamic changes essential for the treatment effect. We review the evidence from preclinical and clinical studies related to TIME, STIE, and their significance on overall survival, through different immunomodulatory pathways, such as metabolic and neuro-immunological pathways. We also evaluate the significance of the STIE, TIME, and their interactions as well as changes after local radiotherapy and systemic immunotherapy or combined immunotherapy. We focus our review on the evidence of lung cancer, hepatocellular carcinoma, and nasopharyngeal carcinoma, aiming to reshape STIE and TIME to enhance immunotherapy efficacy.

Application of Proteomics in the Discovery of Radiosensitive Cancer Biomarkers

Radiation therapy remains an important component of cancer treatment. Gene-encoded proteins were the actual executors of cellular functions. Proteomic was a novel technology that can systematically analysis protein composition and measure their levels of change, this was a high throughput method, and were the import tools in the post genomic era. In recent years, rapid progress of proteomic have been made in the study of cancer mechanism, diagnosis, and treatment. This article elaborates current advances and future directions of proteomics in the discovery of radiosensitive cancer biomarkers.

The role of tumor acidification in aggressiveness, cell dissemination and treatment resistance of oral squamous cell carcinoma

AIMS

To investigate the role of tumor acidification in cell behavior, migration, and treatment resistance of oral squamous cell carcinoma (OSCC).

MAIN METHODS

The SCC4 and SCC25 cell lines were exposed to acidified (pH 6.8) cell culture medium for 7 days. Alternatively, a long-term acidosis was induced for 21 days. In addition, to mimic dynamic pH fluctuation of the tumor microenvironment, cells were reconditioned to neutral pH after experimental acidosis. This study assessed cell proliferation and viability by sulforhodamine B and flow cytometry. Individual and collective cell migration was analyzed by wound healing, time lapse, and transwell assays. Modifications of cell phenotype, EMT induction and stemness potential were investigated by qRT-PCR, western blot, and immunofluorescence. Finally, resistance to chemo- and radiotherapy of OSCC when exposed to acidified environmental conditions (pH 6.8) was determined.

KEY FINDINGS

The exposure to an acidic microenvironment caused an initial reduction of OSCC cells viability, followed by an adaptation process. Acidic adapted cells acquired a mesenchymal-like phenotype along with increased migration and motility indexes. Moreover, tumoral extracellular acidity was capable to induce cellular stemness and to increase chemo- and radioresistance of oral cancer cells.

SIGNIFICANCE

In summary, the results showed that the acidic microenvironment leads to a more aggressive and treatment resistant OSCC cell population.

Skin Cancers and the Contribution of Rho GTPase Signaling Networks to Their Progression

Skin cancers are the most common cancers worldwide. Among them, melanoma, basal cell carcinoma of the skin and cutaneous squamous cell carcinoma are the three major subtypes. These cancers are characterized by different genetic perturbations even though they are similarly caused by a lifelong exposure to the sun. The main oncogenic drivers of skin cancer initiation have been known for a while, yet it remains unclear what are the molecular events that mediate their oncogenic functions and that contribute to their progression. Moreover, patients with aggressive skin cancers have been known to develop resistance to currently available treatment, which is urging us to identify new therapeutic opportunities based on a better understanding of skin cancer biology. More recently, the contribution of cytoskeletal dynamics and Rho GTPase signaling networks to the progression of skin cancers has been highlighted by several studies. In this review, we underline the various perturbations in the activity and regulation of Rho GTPase network components that contribute to skin cancer development, and we explore the emerging therapeutic opportunities that are surfacing from these studies.

The DNA Damage Response Is Differentially Involved in HPV-Positive and HPV-Negative Radioresistant Head and Neck Squamous Cell Carcinoma

Simple Summary

Head and neck cancers can be divided in two major groups according to their risk factors, being high-risk human papillomavirus related (HPV-positive) and alcohol and tobacco related (HPV-negative) head and neck cancers. The majority of the locally advanced patients are treated with radiotherapy. However, up to 50% of these patients show local recurrences. The majority of these recurrences are linked to resistance to radiotherapy treatment. It is known that the response to DNA damage, also a process called the DNA damage response, is an important factor that determines the effectivity of radiotherapy. Here, we assessed the role of the DNA damage response in the resistance process to radiotherapy of head and neck cancers, by generating head and neck cancer cells resistant to radiotherapy. We show that the DNA damage response is differentially involved in the resistance process of HPV-positive and HPV-negative head and neck cancer cells. More specifically, HPV-positive radiotherapy-resistant cells showed increased ability to repair the DNA damage induced by radiotherapy. HPV-negative radiotherapy-resistant cells showed increased capacity to replicate after radiotherapy treatment. Despite this difference, inhibition of the DNA damage response enhanced the effect of radiotherapy in both groups.

Abstract

Radioresistance is a major cause of recurrences and radiotherapy (RT) failure in head and neck squamous cell carcinoma (HNSCC). DNA damage response (DDR) is known to be important for RT response, but its role in radioresistance is not fully understood. Here, we assessed the role of DDR in the radioresistance process of HNSCC by generating radioresistant clones from both HPV-positive SCC154 and HPV-negative SCC61 cells. We show that fractionated RT decreased RT response of HPV-positive and HPV-negative radioresistant clones in vitro and in vivo. Moreover, HPV-positive and HPV-negative radioresistant clones were characterized by differential DDR response. HPV-positive radioresistant clones showed less residual double-strand break damage and increased G2/M arrest recovery after RT, indicating an acquisition of increased DDR kinetics. In contrast, HPV-negative radioresistant clones showed less micronucleated cells after RT and increased survival upon checkpoint inhibition, indicating an increased replicative capacity. Inhibiting key factors of DDR in combination with RT rescued the radioresistant phenotype of both HPV-positive and HPV-negative radioresistant clones. Altogether, our results not only highlight the importance of DDR response in the radioresistance process of HPV-positive and HPV-negative HNSCC, but also provide possibilities for new therapies for HNSCC patients in recurrent settings.

Rho GTPases in cancer radiotherapy and metastasis

Despite treatment advances, radioresistance and metastasis markedly impair the benefits of radiotherapy to patients with malignancies. Functioning as molecular switches, Rho guanosine triphosphatases (GTPases) have well-recognized roles in regulating various downstream signaling pathways in a wide range of cancers. In recent years, accumulating evidence indicates the involvement of Rho GTPases in cancer radiotherapeutic efficacy and metastasis, as well as radiation-induced metastasis. The functions of Rho GTPases in radiotherapeutic efficacy are divergent and context-dependent; thereby, a comprehensive integration of their roles and correlated mechanisms is urgently needed. This review integrates current evidence supporting the roles of Rho GTPases in mediating radiotherapeutic efficacy and the underlying mechanisms. In addition, their correlations with metastasis and radiation-induced metastasis are discussed. Under the prudent application of Rho GTPase inhibitors based on critical evaluations of biological contexts, targeting Rho GTPases can be a promising strategy in overcoming radioresistance and simultaneously reducing the metastatic potential of tumor cells.

Radiotherapy targeting cancer stem cells "awakens" them to induce tumour relapse and metastasis in oral cancer

Radiotherapy is one of the most common treatments for oral cancer. However, in the clinic, recurrence and metastasis of oral cancer occur after radiotherapy, and the underlying mechanism remains unclear. Cancer stem cells (CSCs), considered the “seeds” of cancer, have been confirmed to be in a quiescent state in most established tumours, with their innate radioresistance helping them survive more easily when exposed to radiation than differentiated cancer cells. There is increasing evidence that CSCs play an important role in recurrence and metastasis post-radiotherapy in many cancers. However, little is known about how oral CSCs cause tumour recurrence and metastasis post-radiotherapy. In this review article, we will first summarise methods for the identification of oral CSCs and then focus on the characteristics of a CSC subpopulation induced by radiation, hereafter referred to as “awakened” CSCs, to highlight their response to radiotherapy and potential role in tumour recurrence and metastasis post-radiotherapy as well as potential therapeutics targeting CSCs. In addition, we explore potential therapeutic strategies targeting these “awakened” CSCs to solve the serious clinical challenges of recurrence and metastasis in oral cancer after radiotherapy.

The Role of Cancer Stem Cells in Radiation Resistance

Cancer stem cells (CSC) are a distinct subpopulation within a tumor. They are able to self-renew and differentiate and possess a high capability to repair DNA damage, exhibit low levels of reactive oxygen species (ROS), and proliferate slowly. These features render CSC resistant to various therapies, including radiation therapy (RT). Eradication of all CSC is a requirement for an effective antineoplastic treatment and is therefore of utmost importance for the patient. This makes CSC the prime targets for any therapeutic approach. Albeit clinical data is still scarce, experimental data and first clinical trials give hope that CSC-targeted treatment has the potential to improve antineoplastic therapies, especially for tumors that are known to be treatment resistant, such as glioblastoma. In this review, we will discuss CSC in the context of RT, describe known mechanisms of resistance, examine the possibilities of CSC as biomarkers, and discuss possible new treatment approaches.

Mechanisms of different response to ionizing irradiation in isogenic head and neck cancer cell lines

Background

Treatment options for recurrent head and neck tumours in the previously irradiated area are limited, including re-irradiation due to radioresistance of the recurrent tumour and previous dose received by surrounding normal tissues. As an in vitro model to study radioresistance mechanisms, isogenic cells with different radiosensitivity can be used. However, they are not readily available. Therefore, our objective was to establish and characterize radioresistant isogenic human pharyngeal squamous carcinoma cells and to evaluate early radiation response in isogenic parental, radioresistant and radiosensitive cells.

Methods

Radioresistant cells were derived from parental FaDu cells by repeated exposure to ionizing radiation. Radiosensitivity of the established isogenic radioresistant FaDu-RR cells was evaluated by clonogenic assay and compared to isogenic parental FaDu and radiosensitive 2A3 cells. Additional phenotypic characterization of these isogenic cells with different radiosensitivity included evaluation of chemosensitivity, cell proliferation, cell cycle, radiation-induced apoptosis, resolution of DNA double-strand breaks, and DNA damage and repair signalling gene expression before and after irradiation.

Results

In the newly established radioresistant cells in response to 5 Gy irradiation, we observed no alteration in cell cycle regulation, but delayed induction and enhanced resolution of DNA double-strand breaks, lower induction of apoptosis, and pronounced over-expression of DNA damage signalling genes in comparison to parental cells. On the other hand, radiosensitive 2A3 cells were arrested in G₂/M-phase in response to 5 Gy irradiation, had a prominent accumulation of and slower resolution of DNA double-strand breaks, and no change in DNA damage signalling genes expression.

Conclusions

We concluded that the emergence of the radioresistance in the established radioresistant isogenic cells can be at least partially attributed to the enhanced DNA double-strand break repair, altered expression of DNA damage signalling and repair genes. On the other hand, in radiosensitive isogenic cells the reduced ability to repair a high number of induced DNA double-strand breaks and no transcriptional response in DNA damage signalling genes indicate on a lack of adaptive response to irradiation. Altogether, our results confirmed that these isogenic cells with different radiosensitivity are an appropriate model to study the mechanisms of radioresistance.

Exploring Radiation Response in Two Head and Neck Squamous Carcinoma Cell Lines Through Metabolic Profiling

Head and neck squamous cell carcinoma (HNSCC) is the sixth most common form of cancer worldwide. Radiotherapy, with or without surgery, represents the major approach to curative treatment. However, not all tumors are equally sensitive to irradiation. It is therefore of interest to apply newer system biology approaches (e.g., metabolic profiling) in squamous cancer cells with different radiosensitivities in order to provide new insights on the mechanisms of radiation response. In this study, two cultured HNSCC cell lines from the same donor, UM-SCC-74A and UM-SCC-74B, were first genotyped using Short Tandem Repeat (STR), and assessed for radiation response by the means of clonogenic survival and growth inhibition assays. Thereafter, cells were cultured, irradiated and collected for subsequent metabolic profiling analyses using liquid chromatography-mass spectrometry (LC-MS). STR verified the similarity of UM-SCC-74A and UM-SCC-74B cells, and three independent assays proved UM-SCC-74B to be clearly more radioresistant than UM-SCC-74A. The LC-MS metabolic profiling demonstrated significant differences in the intracellular metabolome of the two cell lines before irradiation, as well as significant alterations after irradiation. The most important differences between the two cell lines before irradiation were connected to nicotinic acid and nicotinamide metabolism and purine metabolism. In the more radiosensitive UM-SCC-74A cells, the most significant alterations after irradiation were linked to tryptophan metabolism. In the more radioresistant UM-SCC-74B cells, the major alterations after irradiation were connected to nicotinic acid and nicotinamide metabolism, purine metabolism, the methionine cycle as well as the serine, and glycine metabolism. The data suggest that the more radioresistant cell line UM-SCC-74B altered the metabolism to control redox-status, manage DNA-repair, and change DNA methylation after irradiation. This provides new insights on the mechanisms of radiation response, which may aid future identification of biomarkers associated with radioresistance of cancer cells.

Research Progress on Long Non-Coding RNA and Radiotherapy

Long non-coding RNAs (lncRNAs), a group of non-protein-coding RNAs longer than 200 nucleotides, are involved in multiple biological and pathological processes, such as proliferation, apoptosis, migration, invasion, angiogenesis, and immune escape. Many studies have shown that lncRNAs participate in the complex network of cancer and play vital roles as oncogenes or tumor-suppressor genes in a variety of cancers. Moreover, recent research has shown that abnormal expression of lncRNAs in malignant tumor cells before and after radiotherapy may participate in the progression of cancers and affect the radiation sensitivity of malignant tumor cells mediated by specific signaling pathways or cell cycle regulation. In this review, we summarize the published studies on lncRNAs in radiotherapy regarding the biological function and mechanism of human cancers, including esophageal cancer, pancreatic cancers, nasopharyngeal carcinoma, hepatocellular carcinoma, cervical cancer, colorectal cancer, and gastric cancer.

Adaptive Responses to Monotherapy in Head and Neck Cancer: Interventions for Rationale-Based Therapeutic Combinations

Most Phase II and III clinical trials in head and neck cancer (HNC) combine two or more treatment modalities, which are based, in part, on knowledge of the molecular mechanisms of innate and acquired resistance to monotherapy. In this review, we describe the range of tumor-cell autonomously derived (intrinsic) and tumor-microenvironment-derived (extrinsic) acquired-resistance mechanisms to various FDA-approved monotherapies for HNC. Specifically, we describe how tumor cells and the tumor microenvironment (TME) respond to radiation, chemotherapy, targeted therapy (cetuximab), and immunotherapies [programmed cell death 1 (PD-1) inhibitors] and adapt to the selective pressure of these monotherapies. Due to the diversity of adaptive responses to monotherapy, monitoring the response to treatment in patients is critical to understand the path that leads to resistance and to guide the optimal therapeutic drug combinations in the clinical setting. We envisage that applying such a rationale-based therapeutic strategy will improve treatment efficacy in HNC patients.

mTOR Signalling in Head and Neck Cancer: Heads Up

The mammalian target of rapamycin (mTOR) signalling pathway is a central regulator of metabolism in all cells. It senses intracellular and extracellular signals and nutrient levels, and coordinates the metabolic requirements for cell growth, survival, and proliferation. Genetic alterations that deregulate mTOR signalling lead to metabolic reprogramming, resulting in the development of several cancers including those of the head and neck. Gain-of-function mutations in EGFR, PIK3CA, and HRAS, or loss-of-function in p53 and PTEN are often associated with mTOR hyperactivation, whereas mutations identified from The Cancer Genome Atlas (TCGA) dataset that potentially lead to aberrant mTOR signalling are found in the EIF4G1, PLD1, RAC1, and SZT2 genes. In this review, we discuss how these mutant genes could affect mTOR signalling and highlight their impact on metabolic processes, as well as suggest potential targets for therapeutic intervention, primarily in head and neck cancer.

LncRNA H19 interacted with miR-130a-3p and miR-17-5p to modify radio-resistance and chemo-sensitivity of cardiac carcinoma cells

The current investigation explored the synthetic contribution of lncRNA H19, miR-130a-3p, and miR-17-5p to radio-resistance and chemo-sensitivity of cardiac cancer cells. Totally 284 human cardiac cancer tissues were gathered, and they have been pathologically diagnosed. The cardiac cancer cells were isolated with utilization of the mechanic method. Moreover, cisplatin, adriamycin, mitomycin, and 5-fluorouracil were designated as the chemotherapies, and single-dose X-rays were managed as the radiotherapy for cardiac cancer cells. We also performed luciferase reporter gene assay to verify the targeted relationship between H19 and miR-130a-3p, as well as between H19 and miR-17-5p. Finally, mice models were established to examine the functions of H19, miR-130a-3p, and miR-17-5p on the development of cardiac cancer. The study results indicated that H19, miR-130a-3p, and miR-17-5p expressions within cardiac cancer tissues were significantly beyond those within adjacent nontumor tissues (P < 0.05), and H19 expression was positively correlated with both miR-130a-3p (r_s  = 0.43) and miR-17-5p (r_s  = 0.49) expressions. The half maximal inhibitory concentrations (IC50) of cisplatin, adriamycin, mitomycin, and 5-fluorouracil for cardiac cancer cells were, respectively, determined as 2.01 μg/mL, 8.35 μg/mL, 24.44 μg/mL, and 166.42 μg/mL. The overexpressed H19, miR-130a-3p, and miR-17-5p appeared to improve the survival rate and viability of cardiac cancer cells that were exposed to chemotherapies and X-rays (all P < 0.05). It was also drawn from luciferase reporter gene assay that H19 could directly target miR-130a-3p and miR-17-5p, thereby modifying the sensitivity of cardiac cancer cells to drugs and X-rays (P < 0.05). Finally, the mice models also produced larger tumor size and higher tumor weight, when H19, miR-130a-3p, or miR-17-5p expressions were up-regulated within them (P < 0.05). In conclusion, H19 could act on miR-130a-3p or miR-17-5p to alter the radio- and chemo-sensitivities of cardiac cancer cells, helping to improve the radio-/chemotherapies for cardiac cancer.

Time-course differential lncRNA and mRNA expressions in radioresistant hypopharyngeal cancer cells

Radioresistance remains a major problem in the treatment of patients with hypopharyngeal squamous cell carcinoma (HSCC). Long noncoding RNAs (lncRNAs) have important roles in the development, invasion, and metastasis of various tumors, including HSCC, but little is known about the role of lncRNAs in cancer radioresistance. The aim of this study was to identify radioresistance-related lncRNAs and mRNAs in radioresistant (RS) hypopharyngeal cancer subclone RS-FaDu cells. In this study, we performed microarray analysis to find the differences in time-course lncRNA and mRNA expression profiles between RS-FaDu and parent FaDu cells after 4 Gy radiation therapy, whose reliability was confirmed by validation experiment. Among these consistently dysregulated lncRNAs, we found that some lncRNAs (e.g., TCONS_00018436) might control resistance of HSCC cells to radiation. Furthermore, our bioinformatics analyses from mRNA/lncRNA microarray data showed that certain lncRNAs or mRNAs potentially are involved in radioresistance of HSCC. Our results from this study laid the foundation for further investigating the roles of these lncRNAs and mRNAs as promising candidates in the occurrence and development of HSCC radioresistance.

Metastatic HPV-related oropharyngeal carcinoma cured with chemoradiotherapy: importance of pretherapy biomolecular assessment

Pretherapy assessment has a crucial role in the management of advanced oropharyngeal carcinoma. The case report represents an example of how translational research may help to optimize the therapeutic options and to choose a well‐shaped therapy adapted to the tumor and the patient.

MAGE-A9 in head and neck cancer: Prognostic value and preclinical findings in the context of irradiation

Radiotherapy alone, or as an addition to surgery is important for the treatment of head and neck squamous cell carcinoma (HNSCC). In addition to their expression in germ cells, melanoma associated antigens-A (MAGE-A) are only expressed in malignant tissue. Notably, there is a known correlation between MAGE-A9 expression and poor prognosis in HNSCC patients. However, current knowledge regarding the function of MAGE-A9 expression, particularly in the context of irradiation, is limited. MAGE-A9 expression in 37 oral squamous cell carcinoma patents was immunohistochemically determined and analyzed for overall survival by the Kaplan-Meier log-rank test. Next, the expression of MAGE-A9 was determined by reverse transcription-quantitative polymerase chain reaction in HNSCC cell lines prior to and following irradiation with 2 Gray. The radiosensitivity of each cell line was determined using a clonogenic survival assay. There was a significantly (P=0.0468) longer overall survival in patients with a low level of MAGE-A9 expression. The median overall survival in patients with high MAGE-A9 expression was 47% compared to 73% in the group with low MAGE-A9 expression. The cell lines revealed a distinct expression pattern of MAGE-A9. Following irradiation of the cell lines, a significant enhancement of MAGE-A9 mRNA expression levels was observed. The most prominent alteration in MAGE-A9 expression was observed in the most radioresistant cell line. A high MAGE-A9 expression level correlates significantly with lower overall survival in HNSCC patients. Additionally, irradiation increased the MAGE-A9 mRNA levels in all five HNSCC cell lines, and the most resistant cell line demonstrated the greatest increase in MAGE-A9 expression following irradiation.

Rac1 overexpression is correlated with epithelial mesenchymal transition and predicts poor prognosis in non-small cell lung cancer

Objective: Ras-related C3 botulinum toxin substrate1(Rac1) and epithelial mesenchymal transition (EMT) are key therapeutic targets in cancer. We investigated the clinical significance of Rac1 and markers of EMT expression in non-small cell lung cancer (NSCLC), and their possible correlation with EMT phenotype. Methods: Immunohistochemistry was used to assess the expression of Rac1, Snail1, Twist1, N-cadherin (N-cad), Vimentin (Vim), and E-cadherin (E-cad) in 153 NSCLC paraffin-embedded specimens and 45 normal specimens adjacent to tumors. The correlation of Rac1 and EMT markers with clinicopathological characteristics and the relationship between the protein levels and progression-free survival (PFS) and overall survival (OS) were analyzed. Results: Compared with non-tumor tissues, the NSCLC tissues showed marked elevation in the levels of Rac1, Snail1, Twist1, N-cad, and Vim levels, whereas the E-cad levels were significantly decreased (P < 0.05). The aberrant expression of Rac1 and EMT markers was significantly associated with TNM stage and metastasis (P < 0.05). Increased expression of Rac1 may be associated with poor OS and PFS compared with low expression (P<0.001 and P=0.004). Significant correlations were observed between the EMT markers expressed and OS or PFS(P<0.01). In addition, multivariate analysis indicated that the expression of Rac1, Snail1, Twist1, N-cad, Vim, and E-cad was an independent prognostic factor in NSCLC. Interestingly, Rac1 expression was positively correlated with Snail1, Twist1, N-cad, and Vim levels (r=0.563, r=0.440, r=0.247 r=0.536, P<0.01, respectively) and negatively correlated with E-cad levels (r=-0.464, P<0.001) in NSCLC tissues. Rac1, Twist, Snail1, Vim and N-cad were highly expressed in lung cancer patients resistant to radiotherapy, while E-cad was poorly expressed. Conclusion: Rac1 may promote NSCLC progression and metastasis via EMT, which may be considered as a potential therapeutic target.

Inhibition of glutamine metabolism counteracts pancreatic cancer stem cell features and sensitizes cells to radiotherapy

Pancreatic ductal adenocarcinoma (PDAC) cells utilize a novel non-canonical pathway of glutamine metabolism that is essential for tumor growth and redox balance. Inhibition of this metabolic pathway in PDAC can potentially synergize with therapies that increase intracellular reactive oxygen species (ROS) such as radiation. Here, we evaluated the dependence of pancreatic cancer stem cells (PCSCs) on this non-canonical glutamine metabolism pathway and researched whether inhibiting this pathway can enhance radiosensitivity of PCSCs. We showed that glutamine deprivation significantly inhibited self-renewal, decreased expression of stemness-related genes, increased intracellular ROS, and induced apoptosis in PCSCs. These effects were countered by oxaloacetate, but not α-ketoglutarate. Knockdown of glutamic-oxaloacetic transaminase dramatically impaired PCSCs properties, while glutamate dehydrogenase knockdown had a limited effect, suggesting a dependence of PCSCs on non-canonical glutamine metabolism. Additionally, glutamine deprivation significantly increased radiation-induced ROS and sensitized PCSCs to fractionated radiation. Moreover, transaminase inhibitors effectively enhanced ROS generation, promoted radiation sensitivity, and attenuated tumor growth in nude mice following radiation exposure. Our findings reveal that inhibiting the non-canonical pathway of glutamine metabolism enhances the PCSC radiosensitivity and may be an effective adjunct in cancer radiotherapy.

Association of RAC1 Gene Polymorphisms with Primary End-Stage Renal Disease in Chinese Renal Recipients

BACKGROUND/OBJECTIVE

RAC1 gene could influence susceptibility to renal failure by altering the activity and expression of Rac1, which is a member of the Rho family of small GTP-binding proteins. In clinical practice, renal transplantation provides the optimal treatment for people with end-stage renal disease (ESRD). The objective of this present study was to determine whether the RAC1 gene polymorphisms were associated with primary ESRD susceptibility in Chinese renal recipients.

METHODS

Six single nucleotide polymorphisms (SNPs) of RAC1 gene, including rs836488 T>C, rs702482 A>T, rs10951982 G>A, rs702483 A>G, rs6954996 G>A, and rs9374 G>A, were genotyped in 300 renal transplant recipients (cases) and 998 healthy Chinese subjects (controls) by using TaqMan SNP genotyping assay. Allele, genotype, and haplotype frequencies of the six SNPs were compared between cases and controls. Odds ratios (OR) and 95% confidence intervals (CI) were calculated in logistic regression models to evaluate the associations of the six SNPs with ESRD risk.

RESULTS

The genotype distributions for the six SNPs in controls were consistent with Hardy-Weinberg equilibrium (P > 0.05). Association analysis revealed that three SNPs were significantly associated with ESRD risk. Positive associations with ESRD risk were found for the rs836488, rs702482, and rs702483 in the co-dominant model (minor allele homozygotes versus major allele homozygotes); specifically, the frequencies of the minor allele homozygotes and the minor allele for the three SNPs were higher in the cases than in the controls. In addition, these three SNPs also had associations with increased ESRD risk under the additive model (P < 0.05), and positive associations were also found for the rs836488 in the dominant model (P < 0.05) and for the rs702483 in the recessive model (P < 0.05). All these associations were independent of confounding factors. The other three SNPs (rs10951982, rs6954996, and rs9374), in all comparison models, were not associated with ESRD risk (P > 0.05). In haplotype analysis, carriers with "C-T-G-G-G-G" haplotype had a significantly higher risk of ESRD compared with the most common haplotype "T-A-G-A-G-G" (P = 0.011, OR = 1.46, 95% CI = 1.09-1.94).

CONCLUSION

This study suggested that polymorphisms of RAC1 gene might influence the susceptibility to ESRD in Chinese Han population. Further studies are necessary to confirm our findings.

Radiation resistance: Cancer stem cells (CSCs) and their enigmatic pro-survival signaling

Despite the fact that radiation therapy is a highly effective therapeutic approach, a small intratumoral cell subpopulation known as "cancer stem cells" (CSCs) is radiation-resistant and possesses specific molecular properties protecting it against radiation-induced damage. The exact mechanisms of this radioresistance are still not fully elucidated, but they relate to these cells' enhanced DNA repair capacities and their low intracellular ROS concentrations, resulting from their up-regulation of ROS scavengers. The low ROS content is accompanied by disturbances in cell cycle regulation, so it can be assumed that either CSCs are quiescent or dormant themselves, or that this cell population consists of at least two cell subpopulations: the normally and the slowly proliferating cells (quiescent or dormant cells). Slowly dividing CSCs show concomitant dysregulation of the signaling molecules mediating both cell cycle progression and maintenance of cell stemness. Despite a massive accumulation of data concerning the mechanisms underlying DNA damage response in CSCs, it represents a challenge to researchers in the era of personalized medicine to elucidate the role of intracellular ROS and of signaling pathways associated with the radiation resistance of these cells; there is a clear need to understand the molecular mechanisms helping CSCs to survive radiation exposure.

MicroRNA-216a enhances the radiosensitivity of pancreatic cancer cells by inhibiting beclin-1-mediated autophagy

Radioresistance has become a challenge in the treatment of pancreatic cancer, which limits the efficacy and outcomes of radiotherapy in clinical treatment. Autophagy, recognized as an adaptive response to cell stress, has recently been involved in the radioresistance of cancer cells. MicroRNAs (miRNAs) are also involved in the radioresistance of pancreatic cancer cells. In the present study, we established a radioresistant pancreatic cancer cell line and found that miRNA-216a was significantly downregulated whereas the autophagy activity was increased as compared with the control. Forced expression of miR-216a was found to inhibit the expression of beclin-1, a critical autophagic gene, as well as autophagy. Using bioinformatics analysis and the dual-luciferase reporter gene assay, we found that miR-216a directly interacted with 3'-untranslated region (UTR) of beclin-1. Furthermore, the forced expression of miR‑216a inhibited cell growth and colony formation ability and promoted the cell apoptosis of radioresistant pancreatic cancer cells in response to irradiation. By contrast, overexpression of beclin-1 abrogated the effects of miR-216a. Furthermore, miR-216a sensitized xenograft tumor to irradiation treatment and inhibited irradiation-induced autophagy by regulating beclin-1. Collectively, the results demonstrated that miR‑216a enhanced the radiosensitivity of pancreatic cancer cells by inhibiting beclin-1-mediated autophagy, suggesting a promising molecular target for improving the radiotherapy of pancreatic cancer.

Bevacizumab radiosensitizes non-small cell lung cancer xenografts by inhibiting DNA double-strand break repair in endothelial cells

The aims of this study were to evaluate the effects of biweekly bevacizumab administration on a tumor microenvironment and to investigate the mechanisms of radiosensitization that were induced by it. Briefly, bevacizumab was administered intravenously to Balb/c nude mice bearing non-small cell lung cancer (NSCLC) H1975 xenografts; in addition, bevacizumab was added to NSCLC or endothelial cells (ECs) in vitro, followed by irradiation (IR). The anti-tumor efficacy, anti-angiogenic efficacy and repair of DNA double-strand breaks (DSBs) were evaluated. The activation of signaling pathways was determined using immunoprecipitation (IP) and WB analyses. Finally, biweekly bevacizumab administration inhibited the growth of H1975 xenografts and induced vascular normalization periodically. Bevacizumab more significantly increased cellular DSB and EC apoptosis when administered 1 h prior to 12 Gy/1f IR than when administered 5 days prior to IR, thereby inhibiting tumor angiogenesis and growth. In vitro, bevacizumab more effectively increased DSBs and apoptosis prior to IR and inhibited the clonogenic survival of ECs but not NSCLC cells. Using IP and WB analyses, we confirmed that bevacizumab can directly inhibit the phosphorylation of components of the VEGR2/PI3K/Akt/DNA-PKcs signaling pathway that are induced by IR in ECs. In conclusion, bevacizumab radiosensitizes NSCLC xenografts mainly by inhibiting DSB repair in ECs rather than by inducing vascular normalization.

Establishment of a novel human papillomavirus-negative and radiosensitive head and neck squamous cell carcinoma cell line

BACKGROUND

The purpose of this study was to develop a CMCSCC-1 cell line for head and neck cancer research into new therapies for head and neck squamous cell carcinoma (HNSCC).

METHODS

The CMCSCC-1 cell line was isolated from a primary oral tongue tumor specimen of a female patient. Tumor cells were evaluated for biomarkers expression by Western blots, reverse transcriptase-polymerase chain reaction (RT-PCR), fluorescence activated cell sorter, and immunostaining. Cell proliferation in response to radiation was measured by the WST-8 assay.

RESULTS

The characterization analyses revealed a typical epithelial morphology; a doubling time of approximately 24 hours, high tumorigenicity in immunodeficient mice, and upregulated biomarkers. CMCSCC-1 cells were negative for human papillomavirus (HPV) infection, but more sensitive to radiation compared with those FaDu cell lines.

CONCLUSION

CMCSCC-1, a novel oral tongue SCC cell line, was established. It will help in the elucidation of the molecular pathogenesis of HPV-negative radiosensitive tumors. © 2015 Wiley Periodicals, Inc. Head Neck 38: E542-E551, 2015.

Reactive oxygen species and p21Waf1/Cip1 are both essential for p53-mediated senescence of head and neck cancer cells

Treatment of head and neck squamous cell carcinoma, HNSCC, often requires multimodal therapy, including radiation therapy. The efficacy of radiotherapy in controlling locoregional recurrence, the most frequent cause of death from HNSCC, is critically important for patient survival. One potential biomarker to determine radioresistance is TP53 whose alterations are predictive of poor radiation response. DNA-damaging reactive oxygen species (ROS) are a by-product of ionizing radiation that lead to the activation of p53, transcription of p21(cip1/waf1) and, in the case of wild-type TP53 HNSCC cells, cause senescence. The expression of p21 and production of ROS have been associated with the induction of cellular senescence, but the intricate relationship between p21 and ROS and how they work together to induce senescence remains elusive. For the first time, we show that persistent exposure to low levels of the ROS, hydrogen peroxide, leads to the long-term expression of p21 in HNSCC cells with a partially functional TP53, resulting in senescence. We conclude that the level of ROS is crucial in initiating p53's transcription of p21 leading to senescence. It is p21's ability to sustain elevated levels of ROS, in turn, that allows for a long-term oxidative stress, and ensures an active p53-p21-ROS signaling loop. Our data offer a rationale to consider the use of either ROS inducing agents or therapies that increase p21 expression in combination with radiation as approaches in cancer therapy and emphasizes the importance of considering TP53 status when selecting a patient's treatment options.

Aberrant epigenetic modifications in radiation-resistant head and neck cancers

Head and neck cancers are characterized by both genetic and epigenetic aberrations. In treating head and neck cancers, ionizing radiation (IR) is an essential modality in either definitive or adjuvant setting. However, radiation-resistant head and neck cancers are not uncommon. The major biological determinator for IR resistance was previously considered at genetic level because DNA is the major target of irradiation damage. However, in head and neck cancers, recent evidence demonstrated epigenetic disturbance after IR, implicating its role in IR resistance. Hence, this chapter intends to establish an in vitro model for investigating DNA methylation changes in IR-resistant head and neck cancer cells. Bisulfite pyrosequencing is the main methodology it introduced.

Rac1 as a multifunctional therapeutic target to prevent and combat cancer metastasis

Metastatic progression of malignant tumors resistant to conventional therapeutic approaches is an ultimate challenge in clinical oncology. Despite the efforts of basic and clinical researchers, there is still no effective treatment schedule to prevent or combat metastatic spread of malignant tumors. This report presents recent findings that could help in the development of targeted therapeutics directed against the most aggressive and treatment-resistant carcinoma cells. It was demonstrated that HNSCC carcinoma cell lines with acquired treatment resistance possessed increased number of cells with carcinoma stem cell (CSC) properties. Furthermore, resistant cells were characterized by increased expression of Rac1, enhanced cell migration, and accelerated release of proangio- and vasculogenic factors (VEGF-A) and influence on endothelial cell (HMEC-1) migration. Inhibition of Rac1 signaling in the treatment-resistant carcinoma cells can interrupt metastatic process due to anoikis restoration and decrease of cell migration. It is also suggested that carcinoma cells with repressed survival capacities will be characterized by reduced release of proangiogenic factors, resulting in the decrease of endothelial cell migration. Therefore targeting of Rac1-related pathways may be considered as a promising therapeutic approach to prevent or combat metastatic lesions.

Crosstalk between DNA repair and cancer stem cell (CSC) associated intracellular pathways

DNA damaging agents (ionizing radiation and chemotherapeutics) are considered as most effective in cancer treatment. However, there is a subpopulation of carcinoma cells within the tumour demonstrating resistance to DNA damaging treatment approaches. It is suggested that limited tumour response to this kind of therapy can be associated with specific molecular properties of carcinoma stem cells (CSCs) representing the most refractory cell subpopulation. This review article presents novel data about molecular features of CSCs underlying DNA damage response and related intracellular signalling.

Rac1 as a potential therapeutic target for chemo-radioresistant head and neck squamous cell carcinomas (HNSCC)

BACKGROUND

In order to improve therapy for HNSCC patients, novel methods to predict and combat local and/or distant tumour relapses are urgently needed. This study has been dedicated to the hypothesis that Rac1, a Rho GTPase, is implicated in HNSCC insensitivity to chemo-radiotherapy resulting in tumour recurrence development.

METHODS

Parental and radiation-resistant (IRR) HNSCC cells were used to support this hypothesis. All cells were investigated for their sensitivity to ionising radiation and cisplatin, Rac1 activity, its intracellular expression and subcellular localisation. Additionally, tumour tissues obtained from 60 HNSCC patients showing different therapy response were evaluated for intratumoral Rac1 expression.

RESULTS

Radiation-resistant IRR cells also revealed resistance to cisplatin accompanied by increased expression, activity and trend towards nuclear translocation of Rac1 protein. Chemical inhibition of Rac1 expression and activity resulted in significant improvement of HNSCC sensitivity to ionising radiation and cisplatin. Preclinical results were confirmed in clinical samples. Although Rac1 was poorly presented in normal mucosa, tumour tissues revealed increased Rac1 expression. The most pronounced Rac1 presence was observed in HNSCC patients with poor early or late responses to chemo-radiotherapy. Tissues taken at recurrence were characterised not only by enhanced Rac1 expression but also increased nuclear Rac1 content.

CONCLUSIONS

Increased expression, activity and subcellular localisation of Rac1 could be associated with lower early response rate and higher risk of tumour recurrences in HNSCC patients and warrants further validation in larger independent studies. Inhibition of Rac1 activity can be useful in overcoming treatment resistance and could be proposed for HNSCC patients with primary or secondary chemo-radioresistance.

Putative biomarkers and therapeutic targets associated with radiation resistance

Radiation therapy plays an important role in the management of malignant tumors, however, the problem of radiation resistance resulting in tumor recurrences after treatment is still unsolved. The emergence of novel biomarkers to predict cancer cell insensitivity to ionizing radiation could help to improve therapy results in cancer patients receiving radiation therapy. The proteomic approach could be effectively used to identify proteins associated with cancer radiation resistance. It is generally believed that radiation resistance could be associated with cancer stem cell persistence within the tumor. Therefore, determination of the molecular characteristics of cancer stem cells could provide additional possibilities to discover novel biomarkers to predict radiation resistance in cancer patients. This review addresses proteome-based findings that could be used for further biomarker identification and preclinical and clinical validation.

MicroRNA 23b regulates autophagy associated with radioresistance of pancreatic cancer cells

BACKGROUND & AIMS

Tumor resistance to radiation is a challenge in the treatment of patients with pancreatic cancer. Improving our understanding of the mechanisms of radioresistance could lead to strategies to increase patients' response to therapy. We investigated the roles of microRNAs (miRNAs) involved in radioresistance of pancreatic cancer cells.

METHODS

We established radioresistant pancreatic cancer cell lines and used array analysis to compare levels of different miRNAs between radioresistant cell lines and the parental cell lines from which they were derived. We transfected pancreatic cancer cells with miRNA mimics or inhibitors and evaluated their effects on cell radiosensitivity using a clonogenic survival assay. The effects of miRNA on autophagy were determined by transmission electron microscopy and immunoblot analysis. We used a luciferase reporter assay to identify messenger RNA targets of specific miRNAs.

RESULTS

Radioresistant pancreatic cancer cells had reduced levels of the miRNA miR-23b and increased autophagy compared with cells that were not radioresistant. Overexpression of miR-23b inhibited radiation-induced autophagy, whereas an inhibitor of miR-23b promoted autophagy in pancreatic cancer cells. Overexpression of miR-23b sensitized pancreatic cancer cells to radiation. The target of miR-23b, ATG12, was overexpressed in radioresistant cells; levels of ATG12 protein correlated with the occurrence of autophagy. Expression of miR-23b blocked radiation-induced autophagy and sensitized pancreatic cancer cells to radiation. We observed an inverse correlation between the level of miR-23b and autophagy in human pancreatic cancer tissue samples.

CONCLUSIONS

In pancreatic cancer cells, reduced levels of the miRNA miR-23b increase levels of ATG12 and autophagy to promote radioresistance. miR-23b might be used to increase the sensitivity of pancreatic cancer cells to radiation therapy.

The role of re-irradiation of secondary and recurrent head and neck carcinomas. Is it a potentially curative treatment? A practical approach

Despite aggressive efforts to cure head and neck cancer patients, including altered fractionation and the addition of chemotherapy to radiation, locoregional recurrence remains a serious issue to face in clinical practice. Indeed, recurrent and second primary tumors occurring in previously irradiated area are common clinical challenge. Whenever possible, patients are advised to undergo salvage surgery. Nevertheless, few patients are suitable candidates for curative resection. In such cases, chemotherapy alone has traditionally been considered, with a poor response rate. It has been questioned whether re-irradiation toxicity outweighs the potential benefits, considering that the median survival of re-irradiated patients marginally exceeds the benefits observed with chemotherapy alone. However, full-dose re-irradiation is a viable treatment option, offering long-term survival for selected patients. Moreover, several prognostic factors should be considered for patients undergoing re-irradiation, such as basic patient characteristics, performance status, the location and extension of recurrent disease, patient co-morbidities, current speech and swallowing function, the interval from the initial radiation therapy to recurrence, previously received doses by critical structures and prior treatment toxicity. Nevertheless, several questions remain unanswered. The purpose of this review is to evaluate the major issues in the field of re-irradiation regarding the current evidence. Therefore, the major selection criteria and new treatment strategies are discussed to define the ideal candidates to undergo re-irradiation and describe a practical approach to these patients. Given the limited evidence in this field, the optimal treatment of recurrent and second primary cancers remains to be defined. Future prospective study of this approach is warranted.