Assessing patient characteristics and radiation-induced non-targeted effects in vivo for high dose-rate (HDR) brachytherapy

Saving normal tissues - a goal for the ages

Almost since the earliest utilization of ionizing radiation, many within the radiation community have worked toward either preventing (i.e. protecting) normal tissues from unwanted radiation injury or rescuing them from the downstream consequences of exposure. However, despite over a century of such investigations, only incremental gains have been made toward this goal and, with certainty, no outright panacea having been found. In celebration of the 60th anniversary of the International Journal of Radiation Biology and to chronicle the efforts that have been made to date, we undertook a non-rigorous survey of the articles published by normal tissue researchers in this area, using those that have appeared in the aforementioned journal as a road map. Three 'snapshots' of publications on normal tissue countermeasures were taken: the earliest (1959-1963) and most recent (2013-2018) 5-year of issues, as well as a 5-year intermediate span (1987-1991). Limiting the survey solely to articles appearing within International Journal of Radiation Biology likely reduced the number of translational studies interrogated given the basic science tenor of this particular publication. In addition, by taking 'snapshots' rather than considering the entire breadth of the journal's history in this field, important papers that were published during the interim periods were omitted, for which we apologize. Nonetheless, since the journal's inception, we observed that, during the chosen periods, the majority of studies undertaken in the field of normal tissue countermeasures, whether investigating radiation protectants, mitigators or treatments, have focused on agents that interfere with the physical, chemical and/or biological effects known to occur during the acute period following whole body/high single dose exposures. This relatively narrow approach to the reduction of normal tissue effects, especially those that can take months, if not years, to develop, seems to contradict our growing understanding of the progressive complexities of the microenvironmental disruption that follows the initial radiation injury. Given the analytical tools now at our disposal and the enormous benefits that may be reaped in terms of improving patient outcomes, as well as the potential for offering countermeasures to those affected by accidental or mass casualty exposures, it appears time to broaden our approaches to developing normal tissue countermeasures. We have no doubt that the contributors and readership of the International Journal of Radiation Biology will continue to contribute to this effort for the foreseeable future.

Effect of gamma radiation on the production of bystander signals from three earthworm species irradiated in vivo

The effect of gamma radiation delivered over 24 h on the induction of bystander signals of three earthworm species exposed in vivo was investigated: A. chlorotica, A. caliginosa, and E. tetraedra. Worms were exposed to external gamma irradiation (Co-60 source) for 24 h and samples of head, body, and clitellum were dissected from exposed and control worms and placed in culture medium for 24 h at 19 C. The harvested medium was filtered and assayed for expression of bystander signals using both clonogenic and mitochondrial reporter assays. Different responses were observed in the different species and in the different tissues. A. chlorotica worm-treated reporters show insignificant mitochondrial response for all sections, yet a significant clonogenic reduction in survival for body sections. A. caliginosa worm-treated reporters show a significant mitochondrial response for some sections and insignificant mitochondrial response and insignificant reduction in clonogenic survival for the rest. E. tetraedra worms from a control site show significant evidence of bystander signalling, measured by mitochondrial response in reporter cells, for all sections while those harvested from a contaminated site show insignificant changes in baseline signalling when exposed to the challenge dose. In vivo exposure of earthworm species shows evidence of bystander signalling using two different reporter assays. This effect varied between the different species and tissues. There is also evidence of attenuated bystander signalling in worms harvested from a site contaminated with radiation.

Low-dose non-targeted radiation effects in human esophageal adenocarcinoma cell lines

PURPOSE

To investigate non-targeted radiation effects in esophageal adenocarcinoma cell lines (OE19 and OE33) using human keratinocyte and colorectal cancer cell reporters following γ-ray exposure.

MATERIALS AND METHODS

Both clonogenic assays and ratiometric calcium endpoints were used to check for the occurrence of bystander signals in reporter cells.

RESULTS

We report data suggesting that γ-irradiation increases cell killing over the expected linear quadratic (LQ) model levels in the OE19 cell line exposed to doses below 1 Gy, i.e. which may be suggestive to be a low hyper-radiosensitive (HRS) response to direct irradiation. Both EAC cell lines (OE19 and OE33) have the ability to produce bystander signals when irradiated cell conditioned medium (ICCM) is placed onto human keratinocyte reporters, but do not seem to be capable of responding to bystander signals when placed on their autologous reporters. Further work with human keratinocyte reporter models showed statistically significant intracellular calcium fluxes following exposure of the reporters to ICCM harvested from both EAC cell lines exposed to 0.5 Gy.

CONCLUSION

These experiments suggest that the OE19 and OE33 cell lines produce bystander signals in human keratinocyte reporter cells. However, the radiosensitivity of the EAC cell lines used in this study cannot be enhanced by the bystander response since both cell lines could not respond to bystander signals.

Effect of miR-503 Down-Regulation on Growth and Invasion of Esophagus Carcinoma and Related Immune Function

Background

MicroRNA (miR) has been proved to be an important biomarker for tumors because it can regulate occurrence, progression, invasion, and metastasis of cancer. A previous study has shown the involvement of miR-503 in multiple gastrointestinal tumors. Its detailed role and immune regulatory function in esophagus carcinoma, however, remains unknown. This study thus investigated the effect of miR-503 in regulating growth, proliferation, and invasion of esophagus cancer and its influence on cytokine secretion.

Material/Methods

Esophagus carcinoma cell line EC9706 and normal esophageal epithelial cell line HEEC were transfected with miR-503 inhibitor. MTT assay was used to quantify the cell proliferation, and a Transwell chamber was used to evaluate cell invasion. Release of cytokines, including interleukin-2 (IL-2), IL-4, IL-10, and interferon-γ (IFN-γ), was measured by enzyme-linked immunosorbent assay (ELISA).

Results

MiR-503 expression was significantly elevated in esophagus carcinoma cells (p<0.05). The specific inhibition of miR-503 expression remarkably suppressed proliferation and invasion of tumor cells. It can also down-regulated IL-2 and IFN-γ expression and facilitate secretion of IL-4 and IL-10 when compared to the control group (p<0.05 in all ceases).

Conclusions

The inhibition of miR-503 can effectively inhibit tumor progression and improve immune function, suggesting its potency as a novel drug target for esophagus cancer treatment.