Radiation promotes colorectal cancer initiation and progression by inducing senescence-associated inflammatory responses

YWHAZ and TBP are potential reference gene candidates for qPCR analysis of response to radiation therapy in colorectal cancer

The expression profiles of conventional reference genes (RGs), including ACTB and GAPDH, used in quantitative real-time PCR (qPCR), vary depending on tissue types and environmental conditions. We searched for suitable RGs for qPCR to determine the response to radiotherapy in colorectal cancer (CRC) cell lines, organoids, and patient-derived tissues. Ten CRC cell lines (Caco-2, COLO 205, DLD-1, HCT116, HCT-15, HT-29, RKO, SW1116, SW480, and SW620) and organoids were selected and irradiated with 2, 10 or 21 grays (Gy) based on the previous related studies conducted over the last decade. The expression stability of 14 housekeeping genes (HKGs; ACTB, B2M, G6PD, GAPDH, GUSB, HMBS, HPRT1, IPO8, PGK1, PPIA, TBP, TFRC, UBC, and YWHAZ) after irradiation was evaluated using RefFinder using raw quantification cycle (Cq) values obtained from samples before and after irradiation. The expression stability of HKGs were also evaluated for paired fresh frozen tissues or formalin-fixed, paraffin-embedded samples obtained from CRC patients before and after chemoradiotherapy. The expression of YWHAZ and TBP encoding 14-3-3-zeta protein and TATA-binding protein were more stable than the other 12 HKGs in CRC cell lines, organoids, and patient-derived tissues after irradiation. The findings suggest that YWHAZ and TBP are potential RG candidates for normalizing qPCR results in CRC radiotherapy experiments.

High-LET-Radiation-Induced Persistent DNA Damage Response Signaling and Gastrointestinal Cancer Development

Ionizing radiation (IR) dose, dose rate, and linear energy transfer (LET) determine cellular DNA damage quality and quantity. High-LET heavy ions are prevalent in the deep space environment and can deposit a much greater fraction of total energy in a shorter distance within a cell, causing extensive DNA damage relative to the same dose of low-LET photon radiation. Based on the DNA damage tolerance of a cell, cellular responses are initiated for recovery, cell death, senescence, or proliferation, which are determined through a concerted action of signaling networks classified as DNA damage response (DDR) signaling. The IR-induced DDR initiates cell cycle arrest to repair damaged DNA. When DNA damage is beyond the cellular repair capacity, the DDR for cell death is initiated. An alternative DDR-associated anti-proliferative pathway is the onset of cellular senescence with persistent cell cycle arrest, which is primarily a defense mechanism against oncogenesis. Ongoing DNA damage accumulation below the cell death threshold but above the senescence threshold, along with persistent SASP signaling after chronic exposure to space radiation, pose an increased risk of tumorigenesis in the proliferative gastrointestinal (GI) epithelium, where a subset of IR-induced senescent cells can acquire a senescence-associated secretory phenotype (SASP) and potentially drive oncogenic signaling in nearby bystander cells. Moreover, DDR alterations could result in both somatic gene mutations as well as activation of the pro-inflammatory, pro-oncogenic SASP signaling known to accelerate adenoma-to-carcinoma progression during radiation-induced GI cancer development. In this review, we describe the complex interplay between persistent DNA damage, DDR, cellular senescence, and SASP-associated pro-inflammatory oncogenic signaling in the context of GI carcinogenesis.

Countermeasure development against space radiation-induced gastrointestinal carcinogenesis: Current and future perspectives

A significantly higher probability of space radiation-induced gastrointestinal (GI) cancer incidence and mortality after a Mars mission has been projected using biophysical and statistical modeling approaches, and may exceed the current NASA mandated limit of less than 3% REID (risk of exposure-induced death). Since spacecraft shielding is not fully effective against heavy-ion space radiation, there is an unmet need to develop an effective medical countermeasure (MCM) strategy against heavy-ion space radiation-induced GI carcinogenesis to safeguard astronauts. In the past, we have successfully applied a GI cancer mouse model approach to understand space radiation-induced GI cancer risk and associated molecular signaling events. We have also tested several potential MCMs to safeguard astronauts during and after a prolonged space mission. In this review, we provide an updated summary of MCM testing using the GI cancer mouse model approach, lessons learned, and a perspective on the senescence signaling targeting approach for desirable protection against space radiation-induced GI carcinogenesis. Furthermore, we also discuss some of the advanced senotherapeutic candidates/combinations as a potential MCM for space radiation-induced GI carcinogenesis.

Trabectedin suppresses escape from therapy-induced senescence in tumor cells by interfering with glutamine metabolism

Conventional and targeted cancer therapies may induce a cellular senescence program termed therapy-induced senescence. However, unlike normal cells, cancer cells are able to evade the senescence cell cycle arrest and to resume proliferation, driving tumor recurrence after treatments. Cells that escape from therapy-induced senescence are characterized by a plastic, cancer stem cell-like phenotype, and recent studies are beginning to define their unique metabolic features, such as glutamine dependence. Here, we show that the antineoplastic drug trabectedin suppresses escape from therapy-induced senescence in all cell lines studied, and reduces breast cancer stem-like cells, at concentrations that do not affect the viability of senescent tumor cells. We demonstrate that trabectedin downregulates both the glutamine transporter SLC1A5 and glutamine synthetase, thereby interfering with glutamine metabolism. On the whole, our results indicate that trabectedin targets a glutamine-dependent cancer stem-like cell population involved in evasion from therapy-induced senescence and suggest a therapeutic potential for trabectedin combined with pro-senescence chemotherapy in tumor treatment.

Sorafenib, rapamycin, and venetoclax attenuate doxorubicin-induced senescence and promote apoptosis in HCT116 cells

Emerging evidence has shown that the therapy-induced senescent growth arrest in cancer cells is of durable nature whereby a subset of cells can reinstate proliferative capacity. Promising new drugs named senolytics selectively target senescent cells and commit them into apoptosis. Accordingly, senolytics have been proposed as adjuvant cancer treatment to cull senescent tumor cells, and thus, screening for agents that exhibit senolytic properties is highly warranted. Our study aimed to investigate three agents, sorafenib, rapamycin, and venetoclax for their senolytic potential in doxorubicin-induced senescence in HCT116 cells. HCT116 cells were treated with one of the three agents, sorafenib (5 µM), rapamycin (100 nM), or venetoclax (10 µM), in the absence or presence of doxorubicin (1 µM). Senescence was evaluated using microscopy-based and flow cytometry-based Senescence-associated-β-galactosidase staining (SA-β-gal), while apoptosis was assessed using annexin V-FITC/PI, and Muse caspase-3/-7 activity assays. We screened for potential genes through which the three drugs exerted senolytic-like action using the Human Cancer Pathway Finder PCR array. The three agents reduced doxorubicin-induced senescent cell subpopulations and significantly enhanced the apoptotic effect of doxorubicin compared with those treated only with doxorubicin. The senescence genes IGFBP5 and BMI1 and the apoptosis genes CASP7 and CASP9 emerged as candidate genes through which the three drugs exhibited senolytic-like properties. These results suggest that the attenuation of doxorubicin-induced senescence might have shifted HCT116 cells to apoptosis by exposure to the tested pharmacological agents. Our work argues for the use of senolytics to reduce senescence-mediated resistance in tumor cells and to enhance chemotherapy efficacy.

Irradiation at Ultra-High (FLASH) Dose Rates Reduces Acute Normal Tissue Toxicity in the Mouse Gastrointestinal System

PURPOSE

Preclinical studies using ultra-high dose rate (FLASH) irradiation have demonstrated reduced normal tissue toxicity compared with conventional dose rate (CONV) irradiation, although this finding is not universal. We investigated the effect of temporal pulse structure and average dose rate of FLASH compared with CONV irradiation on acute intestinal toxicity.

MATERIALS AND METHODS

Whole abdomens of C3H mice were irradiated with a single fraction to various doses, using a 6 MeV electron linear accelerator with single pulse FLASH (dose rate = 2-6 × 106 Gy/s) or conventional (CONV; 0.25 Gy/s) irradiation. At 3.75 days postirradiation, fresh feces were collected for 16S rRNA sequencing to assess changes in the gut microbiota. A Swiss roll-based crypt assay was used to quantify acute damage to the intestinal crypts to determine how tissue toxicity was affected by the different temporal pulse structures of FLASH delivery.

RESULTS

We found statistically significant improvements in crypt survival for mice irradiated with FLASH at doses between 7.5 and 12.5 Gy, with a dose modifying factor of 1.1 for FLASH (7.5 Gy, P < .01; 10 Gy, P < .05; 12.5 Gy, P < .01). This sparing effect was lost when the delivery time was increased, either by increasing the number of irradiation pulses or by prolonging the time between 2 successive pulses. Sparing was observed for average dose rates of ≥280 Gy/s. Fecal microbiome analysis showed that FLASH irradiation caused fewer changes to the microbiota than CONV irradiation.

CONCLUSIONS

This study demonstrates that FLASH irradiation can spare mouse small intestinal crypts and reduce changes in gut microbiome composition compared with CONV irradiation. The higher the average dose rate, the larger the FLASH effect, which is also influenced by temporal pulse structure of the delivery.

Dental pulp stem cell-derived small extracellular vesicle in irradiation-induced senescence

Small extracellular vesicles (sEV) facilitate signaling molecule transfer among cells. We examined the therapeutic efficacy of human dental pulp stem cell-derived sEV (hDPSC-sEV) against cellular senescence in an irradiated-submandibular gland mouse model. Seven-week-old mice were exposed to 25 Gy radiation and randomly assigned to control, phosphate-buffered saline (PBS), or hDPSC-sEV groups. At 18 days post-irradiation, saliva production was measured; histological and reverse transcription-quantitative PCR analyses of the submandibular glands were performed. The salivary flow rate did not differ significantly between the PBS and hDPSC-sEV groups. AQP5-expressing acinar cell numbers and AQP5 expression levels in the submandibular glands were higher in the hDPSC-sEV group than in the other groups. Furthermore, compared with non-irradiated mice, mice in the 25 Gy + PBS group showed a high senescence-associated-β-galactosidase-positive cell number and upregulated senescence-related gene (p16^INK4a, p19^Arf, p21) and senescence-associated secretory phenotypic factor (MMP3, IL-6, PAI-1, NF-κB, and TGF-β) expression, all of which were downregulated in the hDPSC-sEV group. Superoxide dismutase levels were lower in the PBS group than in the hDPSC-sEV group. In summary, hDPSC-sEV reduced inflammatory cytokine and senescence-related gene expression and reversed oxidative stress in submandibular cells, thereby preventing irradiation-induced cellular senescence. Based on these results, we hope to contribute to the development of innovative treatment methods for salivary gland dysfunction that develops after radiotherapy for head and neck cancer.

Glutamine promotes escape from therapy-induced senescence in tumor cells

Therapy-induced senescence (TIS) is a major cellular response to anticancer therapies. While induction of a persistent growth arrest would be a desirable outcome in cancer therapy, it has been shown that, unlike normal cells, cancer cells are able to evade the senescence cell cycle arrest and to resume proliferation, likely contributing to tumor relapse. Notably, cells that escape from TIS acquire a plastic, stem cell-like phenotype. The metabolic dependencies of cells that evade senescence have not been thoroughly studied. In this study, we show that glutamine depletion inhibits escape from TIS in all cell lines studied, and reduces the stem cell subpopulation. In line with a metabolic reliance on glutamine, escaped clones overexpress the glutamine transporter SLC1A5. We also demonstrate a central role of glutamine synthetase that mediates resistance to glutamine deprivation, conferring independence from exogenous glutamine. Finally, rescue experiments demonstrate that glutamine provides nitrogen for nucleotides biosynthesis in cells that escape from TIS, but also suggest a critical involvement of glutamine in other metabolic and non-metabolic pathways. On the whole, these results reveal a metabolic vulnerability of cancer stem cells that recover proliferation after exposure to anticancer therapies, which could be exploited to prevent tumor recurrence.

Comparable radiation sensitivity in p53 wild-type and p53 deficient tumor cells associated with different cell death modalities

Studies of radiation interaction with tumor cells often take apoptosis as the desired results. However, mitotic catastrophe and senescence are also promoted by clinically relevant doses of radiation. Furthermore, p53 is a well-known transcription factor that is closely associated with radiosensitivity and radiation-induced cell death. Therefore, we aimed to investigate the involvement of radiosensitivity, cell death modalities and p53 status in response to carbon-ion radiation (CIR) here. Isogenic human colorectal cancer cell lines HCT116 (p53^+/+ and p53^-/-) were irradiated with high-LET carbon ions. Cell survival was determined by the standard colony-forming assay. 53BP1 foci were visualized to identify the repair kinetics of DNA double-strand breaks (DSBs). Cellular senescence was measured by SA-β-Gal and Ki67 staining. Mitotic catastrophe was determined with DAPI staining. Comparable radiosensitivities of p53^+/+ and p53^-/- HCT116 colorectal cells induced by CIR were demonstrated, as well as persistent 53BP1 foci indicated DNA repair deficiency in both cell lines. Different degree of premature senescence in isogenic HCT116 colorectal cancer cells suggested that CIR-induced premature senescence was more dependent on p21 but not p53. Sustained upregulation of p21 played multifunctional roles in senescence enhancement and apoptosis inhibition in p53^+/+ cells. p21 inhibition further increased radiosensitivity of p53^+/+ cells. Complex cell death modalities rather than single cell death were induced in both p53^+/+ and p53^-/- cells after 5 Gy CIR. Mitotic catastrophe was predominant in p53^-/- cells due to inefficient activation of Chk1 and Chk2 phosphorylation in combination with p53 null. Senescence was the major cell death mechanism in p53^+/+ cells via p21-dependent pathway. Taken together, p21-mediated premature senescence might be used by tumor cells to escape from CIR-induced cytotoxicity, at least for a time.

A Potential Role for Integrin-Linked Kinase in Colorectal Cancer Growth and Progression via Regulating Senescence and Immunity

Integrin-linked kinase (ILK) has been implicated as a molecular driver and mediator in both inflammation and tumorigenesis of the colon. ILK functions as an adaptor and mediator protein linking the extracellular matrix with downstream signaling pathways. ILK is broadly expressed in many human tissues and cells. It is also overexpressed in many cancers, including colorectal cancer (CRC). Inflammation, as evidenced by inflammatory bowel disease (IBD), is one of the highest risk factors for initiating CRC. This has led to the hypothesis that targeting ILK therapeutically could have potential in CRC, as it regulates different cellular processes associated with CRC development and progression as well as inflammation in the colon. A number of studies have indicated an ILK function in senescence, a cellular process that arrests the cell cycle while maintaining active metabolism and transcription. Senescent cells produce different secretions collectively known as the senescence-associated secretory phenotype (SASP). The SASP secretions influence infiltration of different immune cells, either positively for clearing senescent cells or negatively for promoting tumor growth, reflecting the dual role of senescence in cancer. However, a role for ILK in senescence and immunity in CRC remains to be determined. In this review, we discuss the possible role for ILK in senescence and immunity, paying particular attention to the relevance of ILK in CRC. We also examine how activating Toll-like receptors (TLRs) and their agonists in CRC could trigger immune responses against cancer, as a combination therapy with ILK inhibition.

Targeting stemness of cancer stem cells to fight colorectal cancers

Cancer initiating/ stem cells (CSCs) undergo self-renewal and differentiation that contributes to tumor initiation, recurrence and metastasis in colorectal cancer (CRC). Targeting of colorectal cancer stem cells (CCSCs) holds significant promise in eradicating cancer cells and ultimately curing patients with cancer. In this review, we will introduce the current progress of CCSC studies, including the specific surface markers of CCSCs, the intrinsic signaling pathways that regulate the stemness and differentiation characteristics of CCSCs, and the tumor organoid model for CCSC research. We will focus on how these studies will lead to the progress in targeting specific surface markers or signaling pathways on CCSCs by monoclonal antibodies, or by natural or synthetic compounds, or by immunotherapy. As CSCs are highly heterogeneous and plastic, we suggest that combinatory approaches that target the stemness network may represent an important strategy for eradicating cancers.

Identification of a six-gene metabolic signature predicting overall survival for patients with lung adenocarcinoma

Background

Lung cancer is the leading cause of cancer-related deaths worldwide. Lung adenocarcinoma (LUAD) is one of the main subtypes of lung cancer. Hundreds of metabolic genes are altered consistently in LUAD; however, their prognostic role remains to be explored. This study aimed to establish a molecular signature that can predict the prognosis in patients with LUAD based on metabolic gene expression.

Methods

The transcriptome expression profiles and corresponding clinical information of LUAD were obtained from The Cancer Genome Atlas and Gene Expression Omnibus databases. The differentially expressed genes (DEGs) between LUAD and paired non-tumor samples were identified by the Wilcoxon rank sum test. Univariate Cox regression analysis and the lasso Cox regression model were used to construct the best-prognosis molecular signature. A nomogram was established comprising the prognostic model for predicting overall survival. To validate the prognostic ability of the molecular signature and the nomogram, the Kaplan-Meier survival analysis, Cox proportional hazards model, and receiver operating characteristic analysis were used.

Results

The six-gene molecular signature (PFKP, PKM, TPI1, LDHA, PTGES, and TYMS) from the DEGs was constructed to predict the prognosis. The molecular signature demonstrated a robust independent prognostic ability in the training and validation sets. The nomogram including the prognostic model had a greater predictive accuracy than previous systems. Furthermore, a gene set enrichment analysis revealed several significantly enriched metabolic pathways, which suggests a correlation of the molecular signature with metabolic systems and may help explain the underlying mechanisms.

Conclusions

Our study identified a novel six-gene metabolic signature for LUAD prognosis prediction. The molecular signature could reflect the dysregulated metabolic microenvironment, provide potential biomarkers for predicting prognosis, and indicate potential novel metabolic molecular-targeted therapies.

Intestinal stem cells acquire premature senescence and senescence associated secretory phenotype concurrent with persistent DNA damage after heavy ion radiation in mice

Heavy ion radiation, prevalent in outer space and relevant for radiotherapy, is densely ionizing and poses risk to stem cells that are key to intestinal homeostasis. Currently, the molecular spectrum of heavy ion radiation-induced perturbations in intestinal stem cells (ISCs), that could trigger intestinal pathologies, remains largely unexplored. The Lgr5-EGFP-IRES-creERT mice were exposed to 50 cGy of iron radiation. Mice were euthanized 60 d after exposure and ISCs were sorted using fluorescence activated cell sorting. Reactive oxygen species (ROS) and mitochondrial superoxide were measured using fluorescent probes. Since DNA damage is linked to senescence and senescent cells acquire senescence-associated secretory phenotype (SASP), we stained ISCs for both senescence markers p16, p21, and p19 as well as SASP markers IL6, IL8, and VEGF. Due to potential positive effects of SASP on proliferation, we also stained for PCNA. Data show increased ROS and ongoing DNA damage, by staining for γH2AX, and 53BP1, along with accumulation of senescence markers. Results also showed increased SASP markers in senescent cells. Collectively, our data suggest that heavy-ion-induced chronic stress and ongoing DNA damage is promoting SASP in a fraction of the ISCs, which has implications for gastrointestinal function, inflammation, and carcinogenesis in astronauts and patients.

Cellular Senescence and Anti-Cancer Therapy

BACKGROUND

Cellular senescence is generally understood as a permanent cell cycle arrest stemming from different causes. The mechanism of cellular senescence-induced cell cycle arrest is complex, involving interactions between telomere shortening, inflammations and cellular stresses. In recent years, a growing number of studies have revealed that cellular senescence could mediate the cancer progression of neighboring cells, but this idea is controversial and contradictory evidence argues that cellular senescence also contributes to tumor suppression.

OBJECTIVE

Given that the complicated role of senescence in various physiological and pathological scenarios, we try to clarify the precise contribution role of cellular senescence to tumor progression.

METHODS

Search for the information in a large array of relevant articles to support our opinion.

RESULTS

We discuss the relatively widespread occurrence of cellular senescence in cancer treatment and identify the positive and negative side of senescence contributed to tumor progression.

CONCLUSION

We argue that the availability of pro-senescence therapy could represent as a promising regimen for managing cancer disease, particularly with regard to the poor clinical outcome obtained with other anticancer therapies.

Lung cancer progression using fast switching multiple ion beam radiation and countermeasure prevention

Most of the research in understanding space radiation-induced cancer progression and risk assessment has been performed using mono-energetic single-ion beams. However, the space radiation environment consists of a wide variety of ion species with a various range of energies. Using the fast beam switching technology developed at the NASA Space Radiation Laboratory (NSRL) at Brookhaven National Laboratory (BNL), ion species can be switched rapidly allowing investigators to use multiple ions with different energies to simulate more closely the radiation environment found in space. Here, we exposed a lung cancer susceptible mouse model (K-ras^LA-1) to three sequential ion beams: Proton (H) (120 MeV/n) 20 cGy, Helium (He) (250 MeV/n) 5.0 cGy, and Silicon (Si) (300 MeV/n) 5.0 cGy with a dose rate of 0.5 cGy/min. Using three ion beams we performed whole body irradiation with a total dose of 30 cGy in two different orders: 3B-1 (H→He→Si) and 3B-2 (Si→He→H) and used 30 cGy H single-ion beam as a reference. In this study we show that whole-body irradiation with H→He→Si increases the incidence of premalignant lesions and systemic oxidative stress in mice 100 days post-irradiation more than (Si→He→H) and H only irradiation. Additionally, we observed an increase in adenomas with atypia and adenocarcinomas in H→He→Si irradiated mice but not in (Si→He→H) or H (30 cGy) only irradiated mice. When we used the H→He→Si irradiation sequence but skipped a day before exposing the mice to Si, we did not observe the increased incidence of cancer initiation and progression. We also found that a non-toxic anti-inflammatory, anti-oxidative radioprotector (CDDO-EA) reduced H→He→Si induced oxidative stress and cancer initiation almost back to baseline. Thus, exposure to H→He→Si elicits significant changes in lung cancer initiation that can be mitigated using CDDO-EA.

Decellularized mice colons as models to study the contribution of the extracellular matrix to cell behavior and colon cancer progression

Current 3D culture models to study colorectal cancer lack architectural support and signaling proteins provided by the tissue extracellular matrix (ECM) which may influence cell behavior and cancer progression. Therefore, the ability to study cancer cells in the context of a matrix that is physiologically more relevant and to understand how the ECM affects cancer progression has been understudied. To address this, we developed an ex-vivo 3D system, provided by intact wild type (WT) and colon cancer susceptible decellularized mouse colons (DMC), to support the growth of human cancer cells. DMC are free of viable cells but still contain extracellular matrix proteins including subsets of collagens. Stiffness, an important mechanical property, is also maintained in DMCs. Importantly, we observed that the DMC is permissive for cell proliferation and differentiation of a human colon cancer cell line (HT-29). Notably, the ability of cells in the WT DMC to differentiate was also greater when compared to Matrigel™, an extracellular matrix extract from a mouse tumor cell line. Additionally, we observed in invasion assays that DMC obtained from polyps from a colon cancer susceptible mouse model facilitated increased cell migration/invasion of colorectal cancer cells and immortalized non-tumor colonic epithelial cells compared to DMC from WT mice. Finally, using mass spectrometry, we identified extracellular matrix proteins that are more abundant in DMC from a colorectal cancer mouse model compared to age and sex-matched WT mice. We propose that these abundantly expressed proteins in the tumor microenvironment are potentially involved in colorectal cancer progression. STATEMENT OF SIGNIFICANCE: Decellularized matrices, when properly produced, are attractive biomaterials for tissue regeneration and replacement. We show here that the mouse decellularized matrices can also be repurposed to elucidate how the extracellular matrix influences human cell behavior and cancer progression. To do this we produce decellularized matrices, from mice colonic tissue, that have preserved tissue mechanical and structural properties. We demonstrate that the matrix better supports the differentiation of HT-29 cells, a colonic cancer cell line, compared to Matrigel™. Additionally, we show that the extracellular matrix contributes to colon cancer progression via invasion assays using extracellular matrix extracts. Finally, we use mass spectrometry to identify ECM proteins that are more abundant in colonic polyps compared to adjacent tissue regions. This model system may have therapeutic implications for colorectal cancer patients.

Fractionated and Acute Proton Radiation Show Differential Intestinal Tumorigenesis and DNA Damage and Repair Pathway Response in ApcMin/+ Mice

PURPOSE

Proton radiation is a major component of the radiation field in outer space and is used clinically in radiation therapy of resistant cancers. Although epidemiologic studies in atom bomb survivors and radiologic workers have established radiation as a risk factor for colorectal cancer (CRC), we have yet to determine the risk of CRC posed by proton radiation owing to a lack of sufficient human or animal data. The purpose of the current study was to quantitatively and qualitatively characterize differential effects of acute and fractionated high-energy protons on colorectal carcinogenesis.

METHODS AND MATERIALS

We used Apc^Min/+ mice, a well-studied CRC model, to examine acute versus fractionated proton radiation-induced differences in intestinal tumorigenesis and associated signaling pathways. Mice were exposed to 1.88 Gy of proton radiation delivered in a single fraction or in 4 equal daily fractions (0.47 Gy × 4). Intestinal tumor number and grade were scored 100 to 110 days after irradiation, and tumor and tumor-adjacent normal tissues were harvested to assess proliferative β-catenin/Akt pathways and DNA damage response and repair pathways relevant to colorectal carcinogenesis.

RESULTS

Significantly higher intestinal tumor number and grade, along with decreased differentiation, were observed after acute radiation relative to fractionated radiation. Acute protons induced upregulation of β-catenin and Akt pathways with increased proliferative marker phospho-histone H3. Increased DNA damage along with decreased DNA repair factors involved in mismatch repair and nonhomologous end joining were also observed after exposure to acute protons.

CONCLUSIONS

We show increased γH2AX, 53BP1, and 8-oxo-dG, suggesting that increased ongoing DNA damage along with decreased DNA repair factors and increased proliferative responses could be triggering a higher number of intestinal tumors after acute relative to fractionated proton exposures in Apc^Min/+ mice. Taken together, our data suggest greater carcinogenic potential of acute relative to fractionated proton radiation.

Proton therapy for locally advanced non-small cell lung cancer

Radiation therapy is an essential component of treatment for locally advanced non-small cell lung cancer (NSCLC) but can be technically challenging because of the proximity of lung tumors to nearby critical organs or structures. The most effective strategy for reducing radiation-induced toxicity is to reduce unnecessary exposure of normal tissues by using advanced technology; examples from photon (X-ray) therapy have included three-dimensional conformal radiation therapy versus its predecessor, two-dimensional radiation therapy, and intensity-modulated photon radiation therapy versus its predecessor, three-dimensional conformal therapy. Using particle-beam therapy rather than photons offers the potential for further advantages because of the unique depth-dose characteristics of the particles, which can be exploited to allow still higher dose escalation to tumors with greater sparing of normal tissues, with the ultimate goal of improving local tumor control and survival while preserving quality of life by reducing treatment-related toxicity. However, the costs associated with particle therapy with protons are considerably higher than the current state of the art in photon technology, and evidence of clinical benefit from protons is increasingly being demanded to justify the higher financial burden on the healthcare system. Some such evidence is available from preclinical studies, from retrospective, single-institution clinical series, from analyses of national databases, and from single-arm prospective studies in addition to several ongoing randomized comparative trials. This review summarizes the rationale for and challenges of using proton therapy to treat thoracic cancers, reviews the current clinical experience, and suggests topics for future research.

Inflammation-induced DNA damage, mutations and cancer

The relationships between inflammation and cancer are varied and complex. An important connection linking inflammation to cancer development is DNA damage. During inflammation reactive oxygen and nitrogen species (RONS) are created to combat pathogens and to stimulate tissue repair and regeneration, but these chemicals can also damage DNA, which in turn can promote mutations that initiate and promote cancer. DNA repair pathways are essential for preventing DNA damage from causing mutations and cytotoxicity, but RONS can interfere with repair mechanisms, reducing their efficacy. Further, cellular responses to DNA damage, such as damage signaling and cytotoxicity, can promote inflammation, creating a positive feedback loop. Despite coordination of DNA repair and oxidative stress responses, there are nevertheless examples whereby inflammation has been shown to promote mutagenesis, tissue damage, and ultimately carcinogenesis. Here, we discuss the DNA damage-mediated associations between inflammation, mutagenesis and cancer.

Total body irradiation induced mouse small intestine senescence as a late effect

Radiation can induce senescence in many organs and tissues; however, it is still unclear how radiation stimulates senescence in mouse small intestine. In this study, we use the bone marrow transplantation mouse model to explore the late effects of total body irradiation on small intestine. Our results showed that almost all of the body hairs of the irradiated mice were white (which is an indication of aging) 10 months after the exposure to radiation. Furthermore, compared with the age-matched control mice, there were more SA-β-galactosidase (SA-β-gal)-positive cells and an upregulation of p16 and p21 in 8 Gy-irradiated mice intestinal crypts, indicating that radiation induced senescence in the small intestine. Intestinal bacterial flora profile analysis showed that the diversity of the intestinal bacterial flora decreased in irradiated mice; in addition it showed that the principal components of the irradiated and control mice differed: there was increased abundance of Bacteroidia and a decreased abundance of Clostridia in irradiated mice. To explore the underlying mechanism, an RNA-sequence was executed; the results suggested that pancreatic secretion, and the digestion and absorption of proteins, carbohydrates, fats and vitamins were damaged in irradiated mice, which may be responsible for the body weight loss observed in irradiated mice. In summary, our study suggested that total body irradiation may induce senescence in the small intestine and damage the health status of the irradiated mice.

SOX17 overexpression sensitizes chemoradiation response in esophageal cancer by transcriptional down-regulation of DNA repair and damage response genes

Background

Prognosis of esophageal squamous cell carcinoma (ESCC) patients is poor and the concurrent chemoradiation therapy (CCRT) provided to ESCC patients often failed due to resistance. Therefore, development of biomarkers for predicting CCRT response is immensely important. In this study, we evaluated the predicting value of SRY (sex determining region Y)-box 17 (SOX17) protein during CCRT and its dysregulation of transcriptional targets in CCRT resistance in ESCC.

Methods

Pyrosequencing methylation, RT-qPCR and immunohistochemistry assays were performed to examine the DNA methylation, mRNA expression and protein expression levels of SOX17 in endoscopic biopsy from a total of 70 ESCC patients received CCRT. Cell proliferation, clonogenic survival and xenograft growth were used to confirm the sensitization of ESCC cell line KYSE510 in response to cisplatin, radiation or CCRT treatment by SOX17 overexpression in vitro and in vivo. Luciferase activity, RT-qPCR and ChIP-qPCR assays were conducted to examine transcription regulation of SOX17 in KYSE510 parental, KYSE510 radio-resistant cells and their derived xenografts.

Results

High DNA methylation coincided with low mRNA and protein expression levels of SOX17 in pre-treatment endoscopic biopsy from ESCC patients with poor CCRT response. SOX17 protein expression exhibited a good prediction performance in discriminating poor CCRT responders from good responder. Overexpression of SOX17 sensitized KYSE510 radio-resistant cells to cisplatin, radiation or CCRT treatment in cell and xenograft models. Importantly, SOX17 transcriptionally down-regulated DNA repair and damage response-related genes including BRCA1, BRCA2, RAD51, KU80 DNAPK, p21, SIRT1, NFAT5 and REV3L in KYSE510 radio-resistant cells to achieve the sensitization effect to anti-cancer treatment. Low expression of BRCA1, DNAPK, p21, RAD51 and SIRT1 was confirmed in SOX17 sensitized xenograft tissues derived from radio-resistant ESCC cells.

Conclusions

Our study reveals a novel mechanism by which SOX17 transcriptionally inactivates DNA repair and damage response-related genes to sensitize ESCC cell or xenograft to CCRT treatment. In addition, we establish a proof-of-concept CCRT prediction biomarker using SOX17 immunohistochemical staining in pre-treatment endoscopic biopsies to identify ESCC patients who are at high risk of CCRT failure and need intensive care.

Electronic supplementary material

The online version of this article (10.1186/s12929-019-0510-4) contains supplementary material, which is available to authorized users.

Nasoethmoidal Intestinal-Type Adenocarcinoma Treated with Cetuximab: Role of Liquid Biopsy and BEAMing in Predicting Response to Anti-Epidermal Growth Factor Receptor Therapy

Sinonasal intestinal-type adenocarcinomas (SNS-ITAC) are very rare tumors that resemble colorectal cancer in many of their pathological and molecular characteristics. Indeed, in most published series, 10%-14% of SNS-ITAC harbor mutations in KRAS. There is no standard systemic treatment in recurrent or metastatic SNS-ITAC, and there is no evidence of the use of any targeted agent in this entity. We present the case of a recurrent nasoethmoidal ITAC informed as RAS and BRAF wild-type by standard real-time polymerase chain reaction methods and treated with first-line cetuximab and irinotecan without response. Circulating tumor cells coupled to highly sensitive DNA analyses unveiled a mutation in KRAS exon 2 codon 12. Subsequent studies in the primary tumor using BEAMing detected a mutation in the same codon, confirming the KRAS mutated status of the tumor, and possibly explaining the absence of treatment response. This case exemplifies how liquid biopsy can aid in the correct and real-time molecular characterization of tumors even in a rare nonmetastatic cancer of the head and neck. KEY POINTS: Sinonasal intestinal type adenocarcinomas (SNS-ITAC) are rare tumors that commonly develop after a prolonged exposure to organic dusts (wood, leather, etc.), and that resemble colorectal cancer in some of their morphological and molecular characteristics.KRAS mutations have been described in 10%-14% in most series. However, its predictive value for guiding treatment decisions with targeted therapies (i.e., anti-epidermal growth factor receptor [EGFR] therapy) has not been defined.The first case of an SNS-ITAC treated with anti-EGFR therapy (cetuximab) is reported. Analysis of DNA from circulating tumor cells (CTCs) unveiled a mutation in KRAS not detected by standard methods in the primary tumor. However, RAS analysis using BEAMing detected a mutation in the primary tumor in the same codon of KRAS originally detected in CTCs, altogether possibly explaining the lack of treatment response.Liquid biopsy may allow for an accurate molecular diagnosis in rare, organ-confined tumors where few therapeutic options exist. Highly sensitive molecular diagnostics may aid in better characterizing rare entities harboring potentially druggable targets.

Gene Expression Studies for the Development of Particle Therapy

Proton therapy for cancer is now in widespread use, and facilities for carbon ion therapy are showing great promise, but a more complete understanding of the mechanisms underlying particle radiation therapy is still needed in order to optimize treatment. Studies of gene expression, especially those using whole genome techniques, can provide insight into many of the questions still remaining, from the molecular mechanisms involved to predicting patient outcome. This review will summarize gene expression studies of response to proton and carbon ion beams, as well as high-energy protons and high-z high-energy particles with relevance to particle therapy. In general, most such studies find that, in comparison with x-ray or gamma-ray exposure, particle irradiation increases both the number of genes responding and the magnitude of the response. Patterns of gene expression have suggested impacts on specific pathways of relevance to radiation therapy, such as enhancement or suppression of tumor progression or metastasis. However, even within the relatively small number of studies done to date there is no clear consensus of response, suggesting influence by multiple parameters, such as particle type, particle energy, and tumor type. Systematic gene expression studies can help to address these issues, and promoting a culture of data sharing will expedite the process, benefiting investigators across the radiation therapy field.

Proton radiation-induced cancer progression

There are considerable health risks related to ionizing and proton radiation exposure. While there is a long history of health risks associated with ionizing (photon) radiation exposure, there is a limited understanding of the long-term health risks associated with proton radiation exposure. Since proton radiation is becoming more common in cancer therapy, the long-term biological effects of proton radiation remain less well characterized in terms of radiotherapy and well as for astronauts during deep space explorations. In this study, we compared the long-term side effects of proton radiation to equivalent doses of X-rays in the initiation and progression of premalignant lesions in a lung cancer susceptible mouse model (K-ras^LA1). We show proton irradiation causes more complex DNA damage that is not completely repaired resulting in increased oxidative stress in the lungs both acutely and persistently. We further observed K-ras^LA1 mice irradiated with protons had an increased number and size of initiated and premalignant lesions and adenomas that were often infiltrated with inflammatory cells. Proton irradiated mice had a lower median survival and increased carcinoma incidence as compared to unirradiated controls and X-rays exposed mice. Our conclusion is that exposure to proton irradiation enhances the progression of premalignant lesions to invasive carcinomas through persistent DNA damage, chronic oxidative stress, and immunosuppression.

Space radiation triggers persistent stress response, increases senescent signaling, and decreases cell migration in mouse intestine

Coordinated epithelial cell migration is key to maintaining functional integrity and preventing pathological processes in gastrointestinal tissue, and is essential for astronauts’ health and space mission success. Here we show that energetic heavy ions, which are more prevalent in deep space relative to low-Earth orbit, could persistently decrease intestinal epithelial cell migration, alter cytoskeletal remodeling, and increase cell proliferation with ongoing DNA damage and cell senescence, even a year after irradiation. Our study has provided the molecular underpinnings for energetic heavy-ion ⁵⁶Fe radiation-induced cell migration alterations, and raises a potentially serious concern, particularly for long-term deep-space manned missions.

Proliferative gastrointestinal (GI) tissue is radiation-sensitive, and heavy-ion space radiation with its high-linear energy transfer (high-LET) and higher damaging potential than low-LET γ-rays is predicted to compromise astronauts’ GI function. However, much uncertainty remains in our understanding of how heavy ions affect coordinated epithelial cell migration and extrusion, which are essential for GI homeostasis. Here we show using mouse small intestine as a model and BrdU pulse labeling that cell migration along the crypt–villus axis is persistently decreased after a low dose of heavy-ion ⁵⁶Fe radiation relative to control and γ-rays. Wnt/β-catenin and its downstream EphrinB/EphB signaling are key to intestinal epithelial cell (IEC) proliferation and positioning during migration, and both are up-regulated after ⁵⁶Fe radiation. Conversely, factors involved in cell polarity and adhesion and cell–extracellular matrix interactions were persistently down-regulated after ⁵⁶Fe irradiation—potentially altering cytoskeletal remodeling and cell extrusion. ⁵⁶Fe radiation triggered a time-dependent increase in γH2AX foci and senescent cells but without a noticeable increase in apoptosis. Some senescent cells acquired the senescence-associated secretory phenotype, and this was accompanied by increased IEC proliferation, implying a role for progrowth inflammatory factors. Collectively, this study demonstrates a unique phenomenon of heavy-ion radiation-induced persistently delayed IEC migration involving chronic sublethal genotoxic and oncogenic stress-induced altered cytoskeletal dynamics, which were seen even a year later. When considered along with changes in barrier function and nutrient absorption factors as well as increased intestinal tumorigenesis, our in vivo data raise a serious concern for long-duration deep-space manned missions.

Senoptosis: non-lethal DNA cleavage as a route to deep senescence

DNA-damage-induced apoptosis and cellular senescence are perceived as two distinct cell fates. We found that after ionizing radiation (IR)-induced DNA damage the majority (up to 70 %) of senescent human diploid fibroblasts (HDFs) were subjected to controlled cleavage of DNA, resulting in the establishment of a viable and stable sub-G1 population, i.e. deeply senescent cells. We show that in senescent HDFs this DNA cleavage is triggered by modest loss of the mitochondrial membrane potential, which is not sufficient to activate caspases, but strong enough to release mitochondrial endonuclease G (EndoG). We demonstrate that upon γ-irradiation in HDFs EndoG translocates into the nucleus playing an essential role in the non-lethal cleavage of damaged DNA. Notably, the established sub-G1 cell population does not contribute to the senescence-associated secretory phenotype (SASP), however, it exhibits increased senescence-associated β-galactosidase activity. We show that EndoG knockdown causes an increase in DNA damage, indicating a role of this enzyme in DNA repair. Thus, we conclude that IR-induced deep senescence of HDFs exhibits features of both senescence, such as cell cycle arrest and viability, and apoptosis like reduced DNA content and no SASP, and, resembles uncomplete or stalled apoptosis, a phenomenon we term senoptosis.

Shaping functional gut microbiota using dietary bioactives to reduce colon cancer risk

Colon cancer is a multifactorial disease associated with a variety of lifestyle factors. Alterations in the gut microbiota and the intestinal metabolome are noted during colon carcinogenesis, implicating them as critical contributors or results of the disease process. Diet is a known determinant of health, and as a modifier of the gut microbiota and its metabolism, a critical element in maintenance of intestinal health. This review summarizes recent evidence demonstrating the role and responses of the intestinal microbiota during colon tumorigenesis and the ability of dietary bioactive compounds and probiotics to impact colon health from the intestinal lumen to the epithelium and systemically. We first describe changes to the intestinal microbiome, metabolome, and epithelium associated with colon carcinogenesis. This is followed by a discussion of recent evidence indicating how specific classes of dietary bioactives, prebiotics, or probiotics affect colon carcinogenesis. Lastly, we briefly address the prospects of using multiple 'omics' techniques to integrate the effects of diet, host, and microbiota on colon tumorigenesis with the goal of more fully appreciating the interconnectedness of these systems and thus, how these approaches can be used to advance personalized nutrition strategies and nutrition research.