Sustained activation of the FGF1-MEK-ERK pathway inhibits proliferation, invasion and migration and enhances radiosensitivity in mouse angiosarcoma cells

Angiosarcoma is a rare refractory soft-tissue tumor with a poor prognosis and is treated by radiotherapy. The fibroblast growth factor 1 (FGF1) mutant, with enhanced thermostability due to several substituted amino acids, inhibits angiosarcoma cell metastasis, yet the mechanism of action is unclear. This study aims to clarify the FGF1 mutant mechanism of action using ISOS-1 mouse angiosarcoma cells. The wild-type FGF1 or FGF1 mutant was added to ISOS-1 cells and cultured, evaluating cell numbers over time. The invasive and migratory capacity of ISOS-1 cells was assessed by transwell analysis. ISOS-1 cell radiosensitivity was assessed by colony formation assay after X-ray irradiation. To examine whether mitogen-activated protein kinase (MEK) inhibitor counteracts the FGF1 mutant effects, a combination of MEK inhibitor and FGF1 mutant was added to ISOS-1 cells and cultured. The FGF1 mutant was observed to inhibit ISOS-1 cell proliferation, invasion and migration by sustained FGF1 signaling activation. A MEK inhibitor suppressed the FGF1 mutant-induced inhibition of proliferation, invasion and migration of ISOS-1 cells. Furthermore, the FGF1 mutant enhanced radiosensitivity of ISOS-1 cells, but MEK inhibition suppressed the increased radiosensitivity. In addition, we found that the FGF1 mutant strongly inhibits actin polymerization, suggesting that actin cytoskeletal dynamics are closely related to ISOS-1 cell radiosensitivity. Overall, this study demonstrated that in ISOS-1 cells, the FGF1 mutant inhibits proliferation, invasion and migration while enhancing radiosensitivity through sustained activation of the MEK-mediated signaling pathway.

High-Sulfated Hyaluronic Acid Ameliorates Radiation-Induced Intestinal Damage Without Blood Anticoagulation

Purpose

Many growth factors, such as fibroblast growth factors (FGFs), are useful for the treatment or prevention of radiation damage after radiation therapy. Although heparin can be supplemented to increase the therapeutic effects of FGFs, it possesses strong anticoagulant effects, which limit its potential for clinical use. Therefore, chemically sulfated hyaluronic acid (HA) was developed as a safe alternative to heparin. This study examined the involvement of sulfated HA in radioprotective and anticoagulant effects.

Methods and Materials

FGF1 was administered intraperitoneally to BALB/c mice with sulfated HA 24 hours before or after total body irradiation with γ-rays. Several radioprotective effects were examined in the jejunum. The blood coagulation time in the presence of sulfated HA was measured using murine whole blood.

Results

FGF1 with high-sulfated HA (HA-HS) exhibited almost the same level of in vitro mitogenic activity as heparin, whereas FGF1 with HA or low-sulfated HA exhibited almost no mitogenic activity. Furthermore, HA-HS had high binding capability with FGF1. FGF1 with HA-HS significantly promoted crypt survival to the same level as heparin after total body irradiation and reduced radiation-induced apoptosis in crypt cells. Moreover, pretreatment of HA-HS without FGF1 also increased crypt survival and reduced apoptosis. Crypt survival with FGF1 in the presence of HA depended on the extent of sulfation of HA. Moreover, the blood anticoagulant effects of sulfated HA were weaker than those of heparin. As sulfated HA did not promote the reactivity of antithrombin III to thrombin, it did not increase anticoagulative effects to the same extent as heparin.

Conclusions

This study suggested that HA-HS promotes the radioprotective effects of FGF1 without anticoagulant effects. HA-HS has great potential for practical use to promote tissue regeneration after radiation damage.

The FGF1/CPP-C chimera protein protects against intestinal adverse effects of C-ion radiotherapy without exacerbating pancreatic carcinoma

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C-ion radiotherapy is applied to pancreatic carcinoma in the abdominal cavity.

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The FGF1/CPP-C chimeric protein has an intracellular signaling mode.

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FGF1/CPP-C protects against C-ion-induced intestinal damage.

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FGF1/CPP-C inhibits the proliferation and metastasis of pancreatic carcinoma cells.

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FGF1/CPP-C may be useful for C-ion radiotherapy against pancreatic cancer.

Background and purpose

Carbon ion (C-ion) beams are concentrated to irradiate pancreatic carcinoma in the upper abdomen; however, this radiotherapy potentially causes adverse reactions in the gastrointestinal tract. FGF1 is a candidate radioprotector for radiation-induced intestinal damage, but may promote the malignancy of pancreatic cancer. An FGF1/CPP-C chimeric protein was created to enhance the intracellular signaling mode of FGF1 instead of FGFR signaling. The present study investigated the effects of FGF1/CPP-C on the intestinal adverse reactions of C-ion radiotherapy as well as its influence on the malignancy of pancreatic cancer.

Materials and methods

FGF1/CPP-C was administered intraperitoneally to BALB/c mice without heparin 12 h before total body irradiation (TBI) with low-LET C-ion (17 keV/μm) at 6–8 Gy. Several radioprotective effects were examined in the jejunum. The invasion and migration of the human pancreatic carcinoma cell lines MIAPaCa-2 and PANC-1 were assessed using Boyden chambers after cultures with FGF1/CPP-C.

Results

The FGF1/CPP-C treatment promoted crypt survival after C-ion irradiation at 7–8 Gy significantly more than the FGF1 treatment. FGF1/CPP-C also inhibited C-ion radiotherapy-induced apoptosis and reduced γH2AX foci in crypt cells more than FGF1. However, FGF1/CPP-C inhibited the downstream signaling pathways of FGFRs and suppressed the activation of cell-cycle regulatory molecules in the intestine until 4 h after TBI. Furthermore, IEC6 cells were arrested in G2M after cultures with FGF1/CPP-C or FGF1, suggesting that DNA repair after irradiation is promoted by FGF1/CPP-C-induced G2M arrest. In contrast, FGF1/CPP-C appeared to be internalized into MIAPaCa-2 and PANC-1 cells more efficiently than FGF1. Therefore, FGF1/CPP-C reduced the in vitro proliferation, invasion, and migration of MIAPaCa-2 and PANC-1 cells significantly more than FGF1 through the cellular internalization of FGF1.

Conclusion

These results suggest that the intracellular signaling mode of FGF1/CPP-C attenuates the intestinal adverse effects of C-ion radiotherapy without enhancing the malignancy of pancreatic carcinoma.

Strong radioprotective FGF1 signaling down-regulates proliferative and metastatic capabilities of the angiosarcoma cell line, ISOS-1, through the dual inhibition of EGFR and VEGFR pathways

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Angiosarcoma is associated with a poor prognosis and is treated with radiotherapy.

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Highly stable FGF1 mutants exhibit stronger mitogenic activity than wild-type FGF1 and are candidates for radioprotectors.

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They were examined as strong signaling agonists to clarify the effects of FGF1 on the murine angiosarcoma cell line ISOS-1.

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Strong FGF1 signaling reduced the proliferative, invasive, and migration capabilities of ISOS-1cells.

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Their malignancy was reduced through the dual inhibition of EGFR and VEGFR pathways by strong FGF1 signaling.

Background and purpose

Angiosarcoma is associated with a poor prognosis and is treated with radiotherapy. Although FGF1 is a potential radioprotector, the influence of FGF1 on the malignancy of angiosarcoma remains unknown.

Materials and methods

Highly stable FGF1 mutants, which exhibit stronger mitogenic activity than wild-type FGF1, were examined as strong radioprotectors and signaling agonists to clarify the effects of FGF1 on the murine angiosarcoma cell line ISOS-1.

Results

FGF1 mutants reduced colony formation by and the in vitro invasion and migration of ISOS-1 cells, in addition to an increase in radiosensitivity to X-rays. In contrast, an FGFR inhibitor blocked the inhibitory effects of FGF1 mutants on colony formation, invasion, and migration. siRNA targeting the Fgfr1 gene showed that strong FGFR1 signaling reduced colony formation by ISOS-1 cells. However, the FGF1 mutant reduced the activation of VEGFRs and EGFRs in ISOS-1 cells more strongly than wild-type FGF1. Moreover, the inhibition of VEGFRs and EGFRs synergistically reduced colony formation by and invasion and migration of ISOS-1 cells.

Conclusion

These results suggest that strong FGF1 signaling exerts not only radioprotective effects, but also inhibitory effects on proliferative and metastatic capacities of angiosarcoma through the dual inhibition of EGFR and VEGFR pathways.

FGF18 signaling in the hair cycle resting phase determines radioresistance of hair follicles by arresting hair cycling

Purpose

Telogen (resting phase) hair follicles (HFs) are more radioresistant than their anagen (growth phase) counterparts. Fibroblast growth factor (FGF) 18 is strongly expressed in telogen HFs to maintain the telogen phase, whereas several other FGFs exert radioprotective effects; however, the role of FGF18 in the radioresistance of HFs remains unknown. This study focused on clarifying the role of FGF18 in the radioresistance of telogen HFs and its potential as a radioprotector.

Methods and materials

BALB/c mice with telogen or plucking-induced anagen HFs were exposed to total body irradiation with γ-rays at 4 to 12 Gy after intraperitoneal treatment with FGF18 or an FGF receptor inhibitor. A time course analysis was performed histologically and hair growth was observed 14 or 15 days after depilation. Skin specimens were analyzed by DNA microarrays and Western blotting.

Results

Telogen irradiation at 6 Gy resulted in transient cell growth arrest, leading to successful hair growth, whereas anagen irradiation failed to promote hair growth. Telogen irradiation did not induce apoptosis in HFs or reduce HF stem cells, whereas anagen irradiation induced apoptosis and reduced stem cell numbers. The Inhibition of FGF receptor signaling during the telogen phase promoted HF cell proliferation; however, hair failed to grow after irradiation. In contrast, recombinant FGF18 induced transient cell growth arrest after anagen irradiation with enhanced DNA repair, leading to the inhibition of apoptosis, maintenance of HF stem cells, and successful hair growth. Moreover, FGF18 reduced the expression levels of genes promoting G2/M transition as well as the protein expression levels of cyclin B1 and cdc2 in skin, and induced G2/M arrest in the keratinocyte cell line HaCaT.

Conclusions

These results suggest that FGF18 signaling mediates radioresistance in telogen HFs by arresting the cell cycle, and that FGF18 has potential as a radioprotector for radiation-induced alopecia.

A basic fibroblast growth factor analog for protection and mitigation against acute radiation syndromes

The effects of fibroblast growth factors and their potential as broad-spectrum agents to treat and mitigate radiation injury have been studied extensively over the past two decades. This report shows that a peptide mimetic of basic fibroblast growth factor (FGF-P) protects and mitigates against acute radiation syndromes. FGF-P attenuates both sepsis and bleeding in a radiation-induced bone marrow syndrome model and reduces the severity of gastrointestinal and cutaneous syndromes; it should also mitigate combined injuries. FGF-2 and FGF-P induce little or no deleterious inflammation or vascular leakage, which distinguishes them from most other growth factors, angiogenic factors, and cytokines. Although recombinant FGFs have proven safe in several ongoing clinical trials, they are expensive to synthesize, can only be produced in limited quantity, and have limited shelf life. FGF-P mimics the advantageous features of FGF-2 without these disadvantages. This paper shows that FGF-P not only has the potential to be a potent yet safe broad-spectrum medical countermeasure that mitigates acute radiotoxicity but also holds promise for thermal burns, ischemic wound healing, tissue engineering, and stem-cell regeneration.

Cellular internalization of fibroblast growth factor-12 exerts radioprotective effects on intestinal radiation damage independently of FGFR signaling

PURPOSE

Several fibroblast growth factors (FGFs) were shown to inhibit radiation-induced tissue damage through FGF receptor (FGFR) signaling; however, this signaling was also found to be involved in the pathogenesis of several malignant tumors. In contrast, FGF12 cannot activate any FGFRs. Instead, FGF12 can be internalized readily into cells using 2 cell-penetrating peptide domains (CPP-M, CPP-C). Therefore, this study focused on clarifying the role of FGF12 internalization in protection against radiation-induced intestinal injury.

METHODS AND MATERIALS

Each FGF or peptide was administered intraperitoneally to BALB/c mice in the absence of heparin 24 hours before or after total body irradiation with γ rays at 9 to 12 Gy. Several radioprotective effects were examined in the jejunum.

RESULTS

Administration of FGF12 after radiation exposure was as effective as pretreatment in significantly promoting intestinal regeneration, proliferation of crypt cells, and epithelial differentiation. Two domains, comprising amino acid residues 80 to 109 and 140 to 169 of FGF12B, were identified as being responsible for the radioprotective activity, so that deletion of both domains from FGF12B resulted in a reduction in activity. Interestingly, these regions included the CPP-M and CPP-C domains, respectively; however, CPP-C by itself did not show an antiapoptotic effect. In addition, FGF1, prototypic FGF, possesses a domain corresponding to CPP-M, whereas it lacks CPP-C, so the fusion of FGF1 with CPP-C (FGF1/CPP-C) enhanced cellular internalization and increased radioprotective activity. However, FGF1/CPP-C reduced in vitro mitogenic activity through FGFRs compared with FGF1, implying that FGFR signaling might not be essential for promoting the radioprotective effect of FGF1/CPP-C. In addition, internalized FGF12 suppressed the activation of p38α after irradiation, resulting in reduced radiation-induced apoptosis.

CONCLUSIONS

These findings indicate that FGF12 can protect the intestine against radiation-induced injury through its internalization, independently of FGFRs, suggesting that cellular uptake of FGF12 is an alternative signaling pathway useful for cancer radiation therapy.

Regulation of intestinal cytochrome P450 expression by hepatic cytochrome P450: possible involvement of fibroblast growth factor 15 and impact on systemic drug exposure

Tissue-specific deletion of the gene for NADPH-cytochrome P450 (P450) reductase (CPR), the essential electron donor to all microsomal P450 enzymes, in either liver or intestine, leads to upregulation of many P450 genes in the tissue with the Cpr deletion. Here, by studying the liver-specific Cpr-null (LCN) mouse, we examined whether an interorgan regulatory pathway exists, such that a loss of hepatic CPR would cause compensatory changes in intestinal P450 expression and capacity for first-pass metabolism of oral drugs. We show for the first time that intestinal expression of CYP2B, 2C, and 3A proteins was increased in LCN mice by 2- to 3-fold compared with wild-type (WT) mice, accompanied by significant increases in small intestinal microsomal lovastatin-hydroxylase activity and systemic clearance of oral lovastatin (at 5 mg/kg). Additional studies showed that the hepatic Cpr deletion, which caused large decreases in bile acid (BA) levels in the liver, intestine, plasma, and intestinal content, led to drastic decreases in the mRNA levels of intestinal fibroblast growth factor 15 (FGF15), a target gene of the BA receptor farnesoid X receptor. Furthermore, treatment of mice with FGF19 (the human counterpart of mouse FGF15) abolished the difference between WT and LCN mice in small intestinal (SI) CYP3A levels at 6 hours after the treatment. Our findings reveal a previously unrecognized direct role of intestinal FGF15/19 in the regulation of SI P450 expression and may have profound implications for the prediction of drug exposure in patients with compromised hepatic P450 function.

Ionizing radiation leads to the replacement and de novo production of colonic Lgr5(+) stem cells

Tissue stem cells have self-renewal capability throughout their whole life, which is high enough to lead to the accumulation of DNA damage in a stem cell pool. Whether radiation-induced damage accumulates in tissue stem cells remains unknown, but could be investigated if the fate of tissue stem cells could be followed after irradiation. To realize this goal, we used an Lgr5-dependent lineage tracing system that allows the conditional in vivo labeling of Lgr5(+) intestinal stem cells and their progeny. We found that radiation induced loss of Lgr5(+) stem cells in the colon, but not in the duodenum. Interestingly, the loss of colonic Lgr5(+) cells was compensated by de novo production of Lgr5(+) cells, which increased after irradiation. These findings show that ionizing radiation effectively stimulates the turnover of colonic Lgr5(+) stem cells, implying that radiation-induced damage does not accumulate in the colonic Lgr5(+) stem cells by this mechanism.

Nutritional supplementation with L-arginine prevents pelvic radiation-induced changes in morphology, density, and regulating factors of blood vessels in the wall of rat bladder

PURPOSE

To determine whether L-arginine has protective effects against radiation-induced alterations in the morphology and regulatory factors of vesical blood vessels in rats.

METHODS

Male rats aged 3-4 months were divided into groups of 10 animals each: (a) controls, consisting of non-treated animals; (b) radiated-only rats; and (c) radiated rats receiving L-arginine supplementation. Radiation was in one session of 10 Gy and was aimed at the pelvic-abdominal region. L-arginine was administered once a day (0.65 g/kg body weight), starting 7 days before radiation and continuing until killing on the 16th day after radiation. The density, relative area, and wall thickness of blood vessels were measured in the vesical lamina propria using histological methods, and the expression of vascular endothelial growth factor (VEGF) and fibroblast growth factors (FGF) in the bladder wall was assessed by RT-PCR.

RESULTS

Compared with controls, radiation alone decreased the density and relative area of blood vessels by 32 % (p < 0.01) and 25 % (p < 0.05), respectively, and reduced the arterial wall thickness by 42 % (p < 0.004). VEGF and FGF mRNA levels after radiation were diminished by 67 % (p < 0.002) and 56 % (p < 0.04), respectively. The radiated animals supplemented with L-arginine were not significantly different from controls.

CONCLUSIONS

Pelvic radiation leads to significant vesical modifications, as in the morphology of blood vessels and in VEGF and FGF expression. All these changes, however, were prevented by L-arginine treatment. These results emphasize, therefore, the potential use of this amino acid as a radioprotective drug.

Fibroblast growth factor-23 abolishes 1,25-dihydroxyvitamin D₃-enhanced duodenal calcium transport in male mice

Despite being widely recognized as the important bone-derived phosphaturic hormone, whether fibroblast growth factor (FGF)-23 modulated intestinal calcium absorption remained elusive. Since FGF-23 could reduce the circulating level of 1,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃], FGF-23 probably compromised the 1,25(OH)₂D₃-induced intestinal calcium absorption. FGF-23 may also exert an inhibitory action directly through FGF receptors (FGFR) in the intestinal cells. Herein, we demonstrated by Ussing chamber technique that male mice administered 1 μg/kg 1,25(OH)₂D₃ sc daily for 3 days exhibited increased duodenal calcium absorption, which was abolished by concurrent intravenous injection of recombinant mouse FGF-23. This FGF-23 administration had no effect on the background epithelial electrical properties, i.e., short-circuit current, transepithelial potential difference, and resistance. Immunohistochemical evidence of protein expressions of FGFR isoforms 1-4 in mouse duodenal epithelial cells suggested a possible direct effect of FGF-23 on the intestine. This was supported by the findings that FGF-23 directly added to the serosal compartment of the Ussing chamber and completely abolished the 1,25(OH)₂D₃-induced calcium absorption in the duodenal tissues taken from the 1,25(OH)₂D₃-treated mice. However, direct FGF-23 exposure did not decrease the duodenal calcium absorption without 1,25(OH)₂D₃ preinjection. The observed FGF-23 action was mediated by MAPK/ERK, p38 MAPK, and PKC. Quantitative real-time PCR further showed that FGF-23 diminished the 1,25(OH)₂D₃-induced upregulation of TRPV5, TRPV6, and calbindin-D(9k), but not PMCA(1b) expression in the duodenal epithelial cells. In conclusion, besides being a phosphatonin, FGF-23 was shown to be a novel calcium-regulating hormone that acted directly on the mouse intestine, thereby compromising the 1,25(OH)₂D₃-induced calcium absorption.

Fibroblast growth factor-12 (FGF12) translocation into intestinal epithelial cells is dependent on a novel cell-penetrating peptide domain: involvement of internalization in the in vivo role of exogenous FGF12

The extracellular effect of fibroblast growth factor-12 (FGF12) remains unknown because FGF12 cannot activate any fibroblast growth factor receptors (FGFRs), and FGF12 is not currently thought to be released from cells. We reported previously that FGF12 plays an intracellular role in the inhibition of radiation-induced apoptosis. In this study, we demonstrated that recombinant FGF12 was able to be internalized into the cytoplasm of a rat intestinal epithelial cell line, IEC6, and this process was dependent on two novel cell-penetrating peptide (CPP) domains (CPP-M and CPP-C). In particular, CPP-C, composed of ∼10 amino acids, was identified as a specific domain of FGF12 and its subfamily in the C-terminal region (residues 140-149), although CPP-M was a common domain in the internal region of the FGF family. The absence of CPP-C from FGF12 or a mutation (E142L) in the CPP-C domain drastically reduced the internalization of FGF12 into cells. Therefore, CPP-C played an essential role in the internalization of FGF12. In addition, CPP-C was able to deliver other polypeptides into cells as a CPP because an FGF1/CPP-C chimeric protein was internalized into IEC6 cells more efficiently than wild-type FGF1. Finally, intraperitoneally added FGF12 inhibited radiation-induced apoptosis in the intestinal epithelial cells of BALB/c mice, and deletion of the CPP-C domain decreased the inhibition of the apoptosis. These findings suggest that exogenous FGF12 can play a role in tissues by translocating into cells through the plasma membrane, and the availability of this novel CPP provides a new tool for the intracellular delivery of bioactive molecules.

Post treatment with an FGF chimeric growth factor enhances epithelial cell proliferation to improve recovery from radiation-induced intestinal damage

PURPOSE

A fibroblast growth factor (FGF) 1-FGF2 chimera (FGFC) was created previously and showed greater structural stability than FGF1. This chimera was capable of stimulating epithelial cell proliferation much more strongly than FGF1 or FGF2 even without heparin. Therefore FGFC was expected to have greater biologic activity in vivo. This study evaluated and compared the protective activity of FGFC and FGF1 against radiation-induced intestinal injuries.

METHODS AND MATERIALS

We administered FGFC and FGF1 intraperitoneally to BALB/c mice 24 h before or after total-body irradiation (TBI). The numbers of surviving crypts were determined 3.5 days after TBI with gamma rays at doses ranging from 8 to 12 Gy.

RESULTS

The effect of FGFC was equal to or slightly superior to FGF1 with heparin. However, FGFC was significantly more effective in promoting crypt survival than FGF1 (p < 0.01) when 10 μg of each FGF was administered without heparin before irradiation. In addition, FGFC was significantly more effective at promoting crypt survival (p < 0.05) than FGF1 even when administered without heparin at 24 h after TBI at 10, 11, or 12 Gy. We found that FGFC post treatment significantly promoted 5-bromo-2'-deoxyuridine incorporation into crypts and increased crypt depth, resulting in more epithelial differentiation. However, the number of apoptotic cells in FGFC-treated mice decreased to almost the same level as that in FGF1-treated mice.

CONCLUSIONS

These findings suggest that FGFC strongly enhanced radioprotection with the induction of epithelial proliferation without exogenous heparin after irradiation and is useful in clinical applications for both the prevention and post treatment of radiation injuries.

Radiation countermeasure agents: an update

IMPORTANCE OF THE FIELD

Ionizing radiation (IR) can produce deleterious effects in living tissues, leading to significant morbidity and a potentially fatal illness affecting various organs dose-dependently. As people may be exposed to IR during cancer radiotherapy or as a result of a radiological/nuclear incident or act of terrorism, the danger of irradiation represents a serious public health problem. At present, however, this problem remains largely impervious to medical management. There is, therefore, a pressing need to develop safe and effective radiation countermeasure (RC) agents to prevent, mitigate or treat the harmful consequences of IR exposure.

AREAS COVERED IN THIS REVIEW

Recent advances in the search for RC agents as reflected by the relevant patent literature of the past five years along with peer-reviewed publications are surveyed.

WHAT THE READER WILL GAIN

A total of 43 patents, describing approximately 38 chemically diverse compounds with RC potential are analyzed. These include antioxidants capable of scavenging IR-induced free radicals, modulators of cell death signaling or cell cycle progression, cytokines or growth factors promoting tissue repair and inhibitors of inflammatory cytokines.

TAKE HOME MESSAGE

Several of these RC candidates appear promising, including at least two that are undergoing evaluation for fast-track clinical development.

Microbial influences on the small intestinal response to radiation injury

PURPOSE OF REVIEW

Injury to the small bowel from ionizing radiation occurs commonly in patients undergoing cancer therapy and less commonly in instances of accidental radiation overexposure. Several lines of evidence now suggest that dynamic interactions between the host's enteric microbiota and innate immune system are important in modulating the intestinal response to radiation. Here, we will review recent developments in the area of acute radiation enteropathy and examine the current state of knowledge regarding the impact of host-microbial interactions in the process.

RECENT FINDINGS

There is promise in the development and testing of new clinical biomarkers including serum citrulline. Toll-like receptor agonists and innate immune system signaling pathways including nuclear factor-kappa B profoundly alter intestinal epithelial cell apoptosis and crypt survival after radiation exposure. Germ-free conditions, probiotics and antibiotics are each identified as modifiers of disease development and course. A human study suggested that luminal microbiota composition may influence the host's intestinal response to radiation and may change in those developing postradiation diarrhea.

SUMMARY

New knowledge implies that investigations aimed at deciphering the microbiome-host interactions before and after small bowl radiation injury may eventually allow prediction of disease course and offer opportunities for the development of novel therapeutic or prophylactic strategies.