Low-dose radioimmuno-therapy of cancer

Effect of triple therapy with low-dose total body irradiation and hypo-fractionated radiation plus anti-programmed cell death protein 1 blockade on abscopal antitumor immune responses in breast cancer

Immunostimulatory effects of radiotherapy can be synergistically augmented with immune checkpoint blockade to act both on irradiated tumor lesions and distant, non-irradiated tumor sites. Our hypothesis was that low-dose total body irradiation (L-TBI) combined with hypo-fractionated radiotherapy (H-RT) and anti-programmed cell death protein 1 (aPD-1) checkpoint blockade would enhance the systemic immune response. We tested the efficacy of this triple therapy (L-TBI + H-RT + aPD-1) in BALB/c mice with bilateral breast cancer xenografts. The L-TBI dose was 0.1 Gy. The primary tumor was treated with H-RT (8 Gy × 3). The PD-1 monoclonal antibody was injected intraperitoneally, and the secondary tumors not receiving H-RT were monitored for response. The triple therapy significantly delayed both primary and secondary tumor growths, improved survival rates, and reduced the number of lung metastasis lesions. It increased the activated dendritic and CD8⁺ T cell populations and reduced the infiltration of myeloid-derived suppressor cells in the secondary tumor microenvironment relative to other groups. Thus, L-TBI could be a potential therapeutic modality, and when combined with H-RT and aPD-1, the therapeutic effect could be enhanced significantly.

Effect of X-ray exposure during hysterosalpingography on capabilities of female germ cells

PURPOSE

To elucidate the effect of X-ray exposure during hysterosalpingography (HSG) on subsequent laboratory outcomes in in vitro fertilization (IVF).

METHODS

A total of 1458 oocytes, consisting of 990 oocytes retrieved from 70 women (89 cycles) who underwent HSG prior to IVF and 468 oocytes from 45 women (57 cycles) who underwent IVF without HSG, were evaluated for their retrieval number, maturity, fertilization, and development post fertilization. X-ray exposure during HSG was recorded as reference air kerma (RAK) (mGy). Subjects were stratified according to the amount of RAK (Nil: IVF without HSG, L-RAK: RAK < 16.23, mH-RAK: RAK ≥ 16.23). The number of oocytes retrieved, oocyte maturation, fertilization, and embryo development was compared among 3 groups. Further, multivariate analyses were performed to investigate the effect of X-ray exposure on laboratory outcomes in IVF.

RESULTS

There was a statistically significant difference in the fertilization rate among 3 groups (Nil: 71.6%, L-RAK: 80.5%, mH-RAK: 78.3%). The good-quality blastocyst rate in mH-RAK (46.2%) was significantly higher than L-RAK (35.3%) and Nil (32.4%). Multivariate analyses revealed that X-ray exposure was associated with higher fertilization, higher blastocyst development, and higher good-quality blastocyst development rates with adjustment for patient age, BMI, ovarian stimulation types, and fertilization methods. Association between X-ray exposure and the number of oocytes retrieved, and oocyte maturation was not confirmed.

CONCLUSIONS

The present study suggests that X-ray exposure of the female reproductive organs during HSG could enhance the potential of oocytes rather than adversely.

Resensitization of cisplatin resistance ovarian cancer cells to cisplatin through pretreatment with low-dose fraction radiation

Objective

Cisplatin is the first‐line chemotherapy for ovarian cancer. However, cisplatin resistance is severely affecting the treatment efficacy. FOXO3a has been reported to be involved in reversing chemotherapy resistance. However, whether low‐dose fraction radiation therapy (LDFRT) can reverse cisplatin resistance remains unclear. This study aimed to explore the effect of LDFRT on cisplatin resistance and its relation with FOXO3a expression in vitro.

Methods

The toxicity of cisplatin on SKOV3/DDP cells was evaluated by CCK8 assay and cell apoptosis was measured by Annexin V‐FITC staining as well as Hoechst33342 staining. The expression of FOXO3a and other relative proteins was measured by western blot.

Results

Our study found that LDFRT enhanced cisplatin‐induced apoptosis of SKOV3/DDP cells and promoted the expression of FOXO3a and pro‐apoptotic protein PUMA. In addition, overexpression of FOXO3a promoted PUMA activity and toxicity of cisplatin on SKOV3/DDP cells.

Conclusion

LDFRT reverses cisplatin resistance of SKOV3/DDP cells possibly by upregulating the expression of FOXO3a and its downstream target PUMA, suggesting that LDFRT might be a potent chemosensitizer for the treatment of ovarian cancer.

Health Impacts of Low-Dose Ionizing Radiation: Current Scientific Debates and Regulatory Issues

Health impacts of low-dose ionizing radiation are significant in important fields such as X-ray imaging, radiation therapy, nuclear power, and others. However, all existing and potential applications are currently challenged by public concerns and regulatory restrictions. We aimed to assess the validity of the linear no-threshold (LNT) model of radiation damage, which is the basis of current regulation, and to assess the justification for this regulation. We have conducted an extensive search in PubMed. Special attention has been given to papers cited in comprehensive reviews of the United States (2006) and French (2005) Academies of Sciences and in the United Nations Scientific Committee on Atomic Radiation 2016 report. Epidemiological data provide essentially no evidence for detrimental health effects below 100 mSv, and several studies suggest beneficial (hormetic) effects. Equally significant, many studies with in vitro and in animal models demonstrate that several mechanisms initiated by low-dose radiation have beneficial effects. Overall, although probably not yet proven to be untrue, LNT has certainly not been proven to be true. At this point, taking into account the high price tag (in both economic and human terms) borne by the LNT-inspired regulation, there is little doubt that the present regulatory burden should be reduced.

Low-dose radiation may be a novel approach to enhance the effectiveness of cancer therapeutics

It has been generally accepted that both natural and man-made sources of ionizing radiation contribute to human exposure and consequently pose a possible risk to human health. However, accumulating evidence has shown that the biological effects of low-dose radiation (LDR) are different from those of high-dose radiation. LDR can stimulate proliferation of normal cells and activate their defense systems, while these biological effects are not observed in some cancer cell types. Although there is still no concordance on this matter, the fact that LDR has the potential to enhance the effects of cancer therapeutics and reduce the toxic side effects of anti-cancer therapy has garnered significant interest. Here, we provide an overview of the current knowledge regarding the experimental data detailing the different responses of normal and cancer tissues to LDR, the underlying mechanisms, and its significance in clinical application.

Radiation-hormesis phenotypes, the related mechanisms and implications for disease prevention and therapy

Humans are continuously exposed to ionizing radiation throughout life from natural sources that include cosmic, solar, and terrestrial. Much harsher natural radiation and chemical environments existed during our planet's early years. Mammals survived the harsher environments via evolutionarily-conserved gifts ̶ a continuously evolving system of stress-induced natural protective measures (i.e., activated natural protection [ANP]). The current protective system is differentially activated by stochastic (i.e., variable) low-radiation-dose thresholds and when optimally activated in mammals includes antioxidants, DNA damage repair, p53-related apoptosis of severely-damaged cells, reactive-oxygen-species (ROS)/reactive-nitrogen-species (RNS)- and cytokine-regulated auxiliary apoptosis that selectively removes aberrant cells (e.g., precancerous cells), suppression of disease promoting inflammation, and immunity against cancer cells. The intercellular-signaling-based protective system is regulated at least in part via epigenetic reprogramming of adaptive-response genes. When the system is optimally activated, it protects against cancer and some other diseases, thereby leading to hormetic phenotypes (e.g., reduced disease incidence to below the baseline level; reduced pain from inflammation-related problems). Here, some expressed radiation hormesis phenotypes and related mechanisms are discussed along with their implications for disease prevention and therapy.

Genetic effects of ionizing radiation--some questions with no answers

There are a lot of questions about genetic effects of ionizing radiation, the main one is does ionizing radiation induce mutations in humans? There is no direct evidence that exposure of parents to radiation leads to excess heritable disease in offspring. What is the difference between human and other species in which radiation induced mutations are easily registered? During evolution germ cell selection ex vivo has been changed to a selection in vivo and we cannot observe such selection of radiation damaged cells in human. Low radiation doses - are they harmful or beneficial? The "hormesis" phenomenon as well as radioadaptive response proves positive effects of low radiation dose. Can analysis of chromosomal aberration rate in lymphocytes be used for dosimetry? Many uncontrolled factors may be responsible for significant mistakes of this method. Why did evolution preserve the bystander effect? This paper is discussion one and its goal is to pay attention on some effects of ionizing radiation.

Radar commentary: Use of linear no-threshold hypothesis in radiation protection regulation in the United States

Radiation protection recommendations advanced by the International Commission on Radiological Protection and National Council on Radiation Protection and Measurements, and many times adopted into regulations by the United States Nuclear Regulatory Commission, need to be based on scientifically justified assumptions and conclusions. The linear no-threshold model assigns risk to every radiation exposure above zero dose and is the current basis for setting radiation protection standards worldwide. This hypothesis is vigorously challenged by many individuals but just as vigorously defended in spite of the uncertainties surrounding health effects at low dose levels. It is clear that at radiation doses below 100 mSv, the effects, if any, are so low as to be unobservable and perhaps, therefore, unknowable. However, the linear no-threshold hypothesis is used routinely to formulate regulatory dose limits for workers and the general public and to derive stochastic radiogenic risk estimates at low doses. This note will show that while the linear no-threshold hypothesis may play a legitimate role in setting radiation protection standards and operating policies, such as establishing dose limits or as part of an operational "as low as is reasonably achievable" (ALARA) policy, it is inappropriate for use in estimating possible cancer risks associated with low-level radiation exposures. It will also demonstrate that the raising, not lowering, of current regulatory dose limits is more solidly supported by the actual observed data on radiation dose and effects. The authors submit that the misuse of the linear no-threshold model for predicting radiation effects in exposed individuals and populations should be discontinued.

Low-dose radiation-induced hormetic effect on hematopoietic reconstitution

PURPOSE

To investigate the effects on hematopoietic reconstitution of recipient mice receiving bone marrow cells (BMC) of donor pre-exposed to low-dose radiation (LDR).

MATERIALS AND METHODS

BMC were irradiated in vitro at various low-dose X-rays radiation. Tritiated thymidine ((3)H-TdR) incorporation was adopted to measure the proliferation of the BMC in vitro, and then the optimal radiation doses were selected for further study in vivo. Irradiated recipient mice (7.5 Gy) were infused by BMC exposed to 6 and 8 cGy. The counts of recipients' peripheral blood cells (PBC) and bone marrow mononuclear cells (BMMNC) were monitored at the 5th, 10th, 15th, and 30th day after BMC infusion. The colony-forming units in the recipient spleens (CFU-S) were calculated at the 10th day after infusion.

RESULTS

Exposed to 6 and 8 cGy, BMC demonstrated significant proliferative activities in vitro. When the recipient mice receiving BMC pre-exposed to low dose radiation (6 and 8 cGy), the counts of white blood cell (WBC), BMMNC and CFU-S were consistently higher than those in control.

CONCLUSIONS

BMC of donor irradiated by LDR in vitro may facilitate the hematopoietic reconstitution of the recipient mice.

Radiation hormesis: historical perspective and implications for low-dose cancer risk assessment

Current guidelines for limiting exposure of humans to ionizing radiation are based on the linear-no-threshold (LNT) hypothesis for radiation carcinogenesis under which cancer risk increases linearly as the radiation dose increases. With the LNT model even a very small dose could cause cancer and the model is used in establishing guidelines for limiting radiation exposure of humans. A slope change at low doses and dose rates is implemented using an empirical dose and dose rate effectiveness factor (DDREF). This imposes usually unacknowledged nonlinearity but not a threshold in the dose-response curve for cancer induction. In contrast, with the hormetic model, low doses of radiation reduce the cancer incidence while it is elevated after high doses. Based on a review of epidemiological and other data for exposure to low radiation doses and dose rates, it was found that the LNT model fails badly. Cancer risk after ordinarily encountered radiation exposure (medical X-rays, natural background radiation, etc.) is much lower than projections based on the LNT model and is often less than the risk for spontaneous cancer (a hormetic response). Understanding the mechanistic basis for hormetic responses will provide new insights about both risks and benefits from low-dose radiation exposure.

Nuclear energy and health: and the benefits of low-dose radiation hormesis

Energy needs worldwide are expected to increase for the foreseeable future, but fuel supplies are limited. Nuclear reactors could supply much of the energy demand in a safe, sustainable manner were it not for fear of potential releases of radioactivity. Such releases would likely deliver a low dose or dose rate of radiation, within the range of naturally occurring radiation, to which life is already accustomed. The key areas of concern are discussed. Studies of actual health effects, especially thyroid cancers, following exposures are assessed. Radiation hormesis is explained, pointing out that beneficial effects are expected following a low dose or dose rate because protective responses against stresses are stimulated. The notions that no amount of radiation is small enough to be harmless and that a nuclear accident could kill hundreds of thousands are challenged in light of experience: more than a century with radiation and six decades with reactors. If nuclear energy is to play a significant role in meeting future needs, regulatory authorities must examine the scientific evidence and communicate the real health effects of nuclear radiation. Negative images and implications of health risks derived by unscientific extrapolations of harmful effects of high doses must be dispelled.