Novel unconventional radiotherapy techniques: Current status and future perspectives - Report from the 2nd international radiation oncology online seminar.

•Improvement of therapeutic ratio by novel unconventional radiotherapy approaches.•Immunomodulation using high-dose spatially fractionated radiotherapy.•Boosting radiation anti-tumor effects by adding an immune-mediated cell killing.

Stereotactic radiosurgery with immunotherapy is associated with improved overall survival in patients with metastatic melanoma or non-small cell lung cancer: a National Cancer Database analysis

PurposeImmunotherapy is now a first-line treatment for metastatic non-small cell lung cancer (NSCLC) and melanomaQuery. It is important to understand the relationship between immunotherapy and radiation to the brain. The aim of this study was to assess the role of stereotactic radiosurgery (SRS) or WBRT in addition to immunotherapy in patients with melanoma or NSCLC metastatic to the brain.Methods/patientsUsing the National Cancer Database, 2951 patients with NSCLC and 936 patients with melanoma treated with immunotherapy were identified. Patients were classified as having received immunotherapy alone, immunotherapy with SRS, or immunotherapy with whole-brain radiation therapy (WBRT). Kaplan–Meier, multivariate Cox regression analyses, and propensity matching were performed to evaluate the impact of adding SRS to immunotherapy on overall survival (OS). Immortal survival bias was accounted for by only including patients who received radiation before immunotherapy and time zero was defined as the start of immunotherapy.Results205(6.9%) and 75(8.0%) patients received immunotherapy with no radiation, 822(27.9%) and 326(34.8%) received SRS and immunotherapy, and 1924(65.2%) and 535(57.2%) received WBRT and immunotherapy for NSCLC and melanoma, respectively. Adding SRS to immunotherapy was associated with improved OS in multivariate analyses (NSCLC HR = 0.81, 95% CI 0.66–0.99, p = 0.044; melanoma HR = 0.63, 95% CI 0.45–0.90, p = 0.011). The addition of WBRT to immunotherapy did not improve OS in patients with melanoma nor NSCLC.ConclusionsThis analysis suggests that treatment with SRS and immunotherapy is associated with improved OS compared to immunotherapy alone for patients with melanoma or NSCLC metastatic to the brain.

Stereotactic radiosurgery with immunotherapy is associated with improved overall survival in patients with metastatic melanoma or non-small cell lung cancer: a National Cancer Database analysis.

PURPOSE: Immunotherapy is now a first-line treatment for metastatic non-small cell lung cancer (NSCLC) and melanomaQuery. It is important to understand the relationship between immunotherapy and radiation to the brain. The aim of this study was to assess the role of stereotactic radiosurgery (SRS) or WBRT in addition to immunotherapy in patients with melanoma or NSCLC metastatic to the brain. METHODS/PATIENTS: Using the National Cancer Database, 2951 patients with NSCLC and 936 patients with melanoma treated with immunotherapy were identified. Patients were classified as having received immunotherapy alone, immunotherapy with SRS, or immunotherapy with whole-brain radiation therapy (WBRT). Kaplan-Meier, multivariate Cox regression analyses, and propensity matching were performed to evaluate the impact of adding SRS to immunotherapy on overall survival (OS). Immortal survival bias was accounted for by only including patients who received radiation before immunotherapy and time zero was defined as the start of immunotherapy. RESULTS: 205(6.9%) and 75(8.0%) patients received immunotherapy with no radiation, 822(27.9%) and 326(34.8%) received SRS and immunotherapy, and 1924(65.2%) and 535(57.2%) received WBRT and immunotherapy for NSCLC and melanoma, respectively. Adding SRS to immunotherapy was associated with improved OS in multivariate analyses (NSCLC HR = 0.81, 95% CI 0.66-0.99, p = 0.044; melanoma HR = 0.63, 95% CI 0.45-0.90, p = 0.011). The addition of WBRT to immunotherapy did not improve OS in patients with melanoma nor NSCLC. CONCLUSIONS: This analysis suggests that treatment with SRS and immunotherapy is associated with improved OS compared to immunotherapy alone for patients with melanoma or NSCLC metastatic to the brain.

Repurposing Radiation Therapy for Immuno-oncology.

Radiation therapy is traditionally used for the local control of tumour growth, but recent studies suggest that radiation therapy can have immunomodulatory properties that can be applied in combination therapy with immunotherapeutic agents. The paradigm of using radiation therapy for immunomodulation in cancer treatment is a rapidly progressing field, with multiple ongoing clinical trials exploring its use in combination with immune checkpoint blockades to induce an abscopal effect. Permutations of radiation therapy regimens, including variations in radiation dosing, radiation planning parameters and radiation modality, are being tested with varying degrees of success. The relative biological effectiveness was a concept introduced in the early days of radiation biology that allows the comparison of local tumour control across various radiation modalities and energies. Similarly, there remains a need for a new concept of comparing the immunological effectiveness of various radiation modalities. In this review, we will provide an overview of immunobiological models for preclinical and clinical monitoring of radiation therapy regimens and introduce the concept of relative immunological effectiveness to compare and screen for immune-activating functions of these regimens.

Preclinical evaluation of radiation and systemic, RGD-targeted, adeno-associated virus phage-TNF gene therapy in a mouse model of spontaneously metastatic melanoma.

The incidence of melanoma in the United States continues to rise, with metastatic lesions notoriously recalcitrant to therapy. There are limited effective treatment options available and a great need for more effective therapies that can be rapidly integrated in the clinic. In this study, we demonstrate that the combination of RGD-targeted adeno-associated virus phage (RGD-AAVP-TNF) with hypofractionated radiation therapy results in synergistic inhibition of primary syngeneic B16 melanoma in a C57 mouse model. Furthermore, this combination appeared to modify the tumor microenvironment, resulting in decreased Tregs in the draining LN and increased tumor-associated macrophages within the primary tumor. Finally, there appeared to be a reduction in metastatic potential and a prolongation of overall survival in the combined treatment group. These results indicate the use of targeted TNF gene therapy vector with radiation treatment could be a valuable treatment option for patients with metastatic melanoma.

Molecular Characterization and Computational Modelling of New Delhi Metallo-ß-Lactamase-5 from an Escherichia coli Isolate (KOEC3) of Bovine Origin.

Emergence of antimicrobial resistance mediated through New Delhi metallo-ß-lactamases (NDMs) is a serious therapeutic challenge. Till date, 16 different NDMs have been described. In this study, we report the molecular and structural characteristics of NDM-5 isolated from an Escherichia coli isolate (KOEC3) of bovine origin. Using PCR amplification, cloning and sequencing of full blaNDM gene, we identified the NDM type as NDM-5. Cloning of full gene in E. coli DH5α and subsequent assessment of antibiotic susceptibility of the transformed cells indicated possible role of native promoter in expression blaNDM-5. Translated amino acid sequence had two substitutions (Val88Leu and Met154Leu) compared to NDM-1. Theoretically deduced isoelectric pH of NDM-5 was 5.88 and instability index was 36.99, indicating a stable protein. From the amino acids sequence, a 3D model of the protein was computed. Analysis of the protein structure elucidated zinc coordination and also revealed a large binding cleft and flexible nature of the protein, which might be the reason for broad substrate range. Docking experiments revealed plausible binding poses for five carbapenem drugs in the vicinity of metal ions. In conclusion, results provided possible explanation for wide range of antibiotics catalyzed by NDM-5 and likely interaction modes with five carbapenem drugs.

Semi-automatic cone beam CT segmentation of in vivo pre-clinical subcutaneous tumours provides an efficient non-invasive alternative for tumour volume measurements.

OBJECTIVE: To evaluate the feasibility and accuracy of using cone beam CT (CBCT) scans obtained in radiation studies using the small-animal radiation research platform to perform semi-automatic tumour segmentation of pre-clinical tumour volumes. METHODS: Volume measurements were evaluated for different anatomical tumour sites, the flank, thigh and dorsum of the hind foot, for a variety of tumour cell lines. The estimated tumour volumes from CBCT and manual calliper measurements using different volume equations were compared with the "gold standard", measured by weighing the tumours following euthanasia and tumour resection. The correlation between tumour volumes estimated with the different methods, compared with the gold standard, was estimated by the Spearman's rank correlation coefficient, root-mean-square deviation and the coefficient of determination. RESULTS: The semi-automatic CBCT volume segmentation performed favourably compared with manual calliper measures for flank tumours ≤2 cm(3) and thigh tumours ≤1 cm(3). For tumours >2 cm(3) or foot tumours, the CBCT method was not able to accurately segment the tumour volumes and manual calliper measures were superior. CONCLUSION: We demonstrated that tumour volumes of flank and thigh tumours, obtained as a part of radiation studies using image-guided small-animal irradiators, can be estimated more efficiently and accurately using semi-automatic segmentation from CBCT scans. ADVANCES IN KNOWLEDGE: This is the first study evaluating tumour volume assessment of pre-clinical subcutaneous tumours in different anatomical sites using on-board CBCT imaging. We also compared the accuracy of the CBCT method to manual calliper measures, using various volume calculation equations.

Effect of dentin powder on setting time of mineral trioxide aggregate: an in vitro study.

AIM: Mineral trioxide aggregate (MTA) is a biomaterial with numerous clinical applications in the field of endodontics. The properties of this material come closest to the requirements of an ideal endodontic repair material. Delayed setting time though may limit the use of MTA in endodontic procedures. Many chemical based additives have influenced the setting time of MTA. The aim of this paper was to evaluate the effect of a natural additive in the form of human dentin powder on setting properties of ProRoot MTA (Dentsply/Tulsa Dental, Tulsa, OK). METHODS: Thirty extracted human teeth were taken to obtain fine dentin powder. The methodology used to obtain dentin powder for the present study was same as performed by Haapsalo et al. The specimens were divided into two groups. The samples were placed in standardized stainless steel ring moulds. The setting time of MTA alone and in equal proportions with dentin powder as an additive was evaluated using Vicats apparatus. RESULTS: MTA mixed with dentin powder showed faster setting time (70 minutes) in comparison to MTA without dentin powder (120 minutes) (P<0.5). CONCLUSION: Although MTA is an ideal retrograde material with increased efficacy due to reduced setting on addition of dentin powder. A combination of MTA with dentin powder might be a viable option in procedures where fast setting of the MTA is critical.

Detection of New Delhi metallo-beta-lactamase and extended-spectrum beta-lactamase genes in Escherichia coli isolated from mastitic milk samples.

In this study, eight Escherichia coli isolates were obtained from milk samples of dairy cattle suffering from clinical/subclinical mastitis. Isolates were characterized for antimicrobial resistance traits and virulence genes. Results revealed that one isolate was harbouring New Delhi metallo-beta-lactamase gene (blaNDM ). Cloning and sequencing of the PCR amplicon confirmed the identity of the gene (GenBank accession no. KC769583) having 100% homology with blaNDM-5 (GenBank accession no. JN104597.1), and this isolate was susceptible to colistin, chloramphenicol and tetracycline only. Moreover, another isolate carried extended-spectrum beta-lactamase (ESBL) gene - blaCTX-M , and all isolates possessed blaTEM gene. Of the eight isolates, only one isolate was positive for shiga toxin gene (stx2), and none were harbouring stx1 gene. Occurrence of New Delhi metallo-beta-lactamase (blaNDM ) in one E. coli isolate and ESBL genes in other isolates poses a potential threat to human health following possible entry and spread through food chain.

Cytidine deaminase single-nucleotide polymorphism is predictive of toxicity from gemcitabine in patients with pancreatic cancer: RTOG 9704.

The aim of this study is to validate the prognostic and predictive value of the non-synonymous cytidine deaminase (CDA) Lys²7Gln polymorphism for hematological toxicity and survival using a randomized phase III adjuvant trial (Radiation Therapy Oncology Group (RTOG) 9704) in pancreatic cancer in which one treatment arm received gemcitabine. CDA is involved in gemcitabine inactivation, and there is conflicting data on the role of the non-synonymous CDA Lys²7Gln polymorphism in predicting toxicity and survival in cancer patients treated with gemcitabine. RTOG 9704 randomized 538 patients after pancreatic resection to receive radiotherapy with either 5-fluorouracil (5-FU) or gemcitabine. CDA Lys²7Gln polymorphism genotype was analyzed. We tested an association between CDA single-nucleotide polymorphism genotype and the survival outcome by the Cox proportional hazard model adjusting for other covariates, as well as toxicity by the logistic regression model. There is statistically significant more severe hematological toxicity in patients treated with gemcitabine with either the homozygote wild-type genotype (Lys/Lys) alone (odds ratio (OR)=0.06, P=0.01), or in combination with the heterozygote (Lys/Gln; OR=0.14, P=0.03) when compared with homozygote variant genotype (Gln/Gln) when adjusted for other covariates. This was not seen in the non-gemcitabine treated arm. There are no genotype differences with respect to survival outcome. In conclusion, in this prospective randomized adjuvant study of patients with pancreatic cancer, the CDA Lys²7Gln polymorphism is validated as a predictive marker of gemcitabine hematological toxicity, but not with treatment response or survival.

A novel strategy for in vivo expansion of transplanted hepatocytes using preparative hepatic irradiation and FasL-induced hepatocellular apoptosis.

A strategy for inducing preferential proliferation of the engrafted hepatocytes over host liver cells should markedly increase the benefit of hepatocyte transplantation for the treatment of liver diseases and ex vivo gene therapy. We hypothesized that preparative hepatic irradiation (HIR) to inhibit host hepatocellular regeneration in combination with the mitotic stimulus of host hepatocellular apoptosis should permit repopulation of the liver by transplanted cells. To test this hypothesis, congeneic normal rat hepatocytes were transplanted into UDP-glucuronosyltransferase (UGT1A1)-deficient jaundiced Gunn rats (a model of Crigler-Najjar syndrome type I), following HIR and adenovirus-mediated FasL gene transfer. Progressive repopulation of the liver by engrafted UGT1A1-proficient hepatocytes over 5 months was demonstrated by the appearance of UGT1A1 protein and enzyme activity in the liver, biliary bilirubin glucuronides secretion, and long-term normalization of serum bilirubin levels. This is the first demonstration of massive hepatic repopulation by transplanted cells by HIR and FasL-induced controlled apoptosis of host liver cells.

Amplification of engrafted hepatocytes by preparative manipulation of the host liver.

Scarcity of donor livers is a major obstacle to the general application of hepatocytes for the development of bioartificial liver assist devices as well as intracorporeal engraftment of hepatocytes for the treatment of inherited metabolic diseases. The number of hepatocytes that can be transplanted into the liver safely in a single sitting also limits the utility of this procedure. These limitations could be addressed by providing preferential proliferative advantage to the transplanted cells. Studies using transgenic mouse recipients or donors have indicated that massive repopulation of the host liver by engrafted hepatocytes requires that the transplanted cells are subjected to a proliferative stimulus to which the host hepatocytes cannot respond. Prevention of host hepatocyte proliferation has been achieved by treatment with a plant alkaloid, retrorsine. Because retrorsine is carcinogenic, we have evaluated preparative irradiation for this purpose. The proliferative stimulus may consist of the loss of hepatic mass (e.g., partial hepatectomy, reperfusion injury or induction of Fas-mediated apoptosis by gene transfer) or administration of stimulants of hepatocellular mitosis (e.g., growth factors or thyroid hormone). Potential applications of these preparative manipulations of the host liver include the treatment of inherited metabolic disorders by transplantation of allogeneic hepatocytes, hepatocyte-mediated ex vivo gene therapy, rescuing liver cancer patients from radiation-induced liver damage, and expansion of human hepatocytes in animal livers.

Hepatocyte-based gene therapy.

Hepatocyte-based gene therapy may be used to replace a missing gene product, confer proliferating ability to cultured hepatocytes, prevent allograft rejection, massively repopulate the host liver, or grow xenogeneic hepatocytes in mammalian liver. Gene transfer into isolated hepatocytes can be accomplished via nonviral or viral vectors, the viral vectors being more useful at this time. Common recombinant viruses that integrate into the host genome include murine leukemia retroviruses and lentiviruses, adenoassociated virus, and the T-antigen-deleted SV40 virus. Episomal viruses, such as adenoviruses, permit efficient gene transfer, but the transgene is lost upon proliferation of the transplanted hepatocyte in the host. Hybrid viruses that combine the high transduction efficiency of adenoviral vectors and the integrative capacity of other vectors, such as adenoassociated viruses, have been designed. Massive repopulation of the liver by transplanted hepatocytes can be achieved if a mitotic stimulus to the transplanted cells is combined with prevention of proliferation of the host hepatocytes. Treatment with a plant alkaloid or retrorsine, or preparative irradiation of the liver can be used to inhibit host hepatocellular proliferation, while partial hepatectomy, expression of Fas ligand, or thyroid hormone administration can be used as a mitotic stimulus to the transplanted cells.

Liver irradiation: a potential preparative regimen for hepatocyte transplantation.

Advances in the understanding of hepatocyte engraftment and repopulation of the host liver have already led to the use of hepatocyte transplantation (HT) with some success in the treatment of inherited and acquired liver diseases. Wider application of HT is severely limited by the unavailability of large number of transplantable hepatocytes and difficulties associated with transplanting an adequate number of cells for achieving therapeutically satisfactory levels of metabolic correction. Therefore, there is a need for preparative regimens that provide a growth advantage to the transplanted (healthy) hepatocytes over the host's own (diseased) hepatocytes so that the former can repopulate the host liver. We have recently shown that when the liver of recipient rats was subjected to radiotherapy and partial hepatectomy before HT, the transplanted hepatocytes engrafted in and massively repopulated the liver, and also ameliorated the adverse clinical and histopathological changes associated with hepatic irradiation. This protocol was then used as a preparative regimen for transplanting normal hepatocytes into jaundice mutant rats (Gunn strain), which lack hepatic bilirubin-uridinediphosphoglucuronate glucuronosyltransferase and is a model of Crigler-Najjar syndrome Type I. The results showed long-term correction of the metabolic abnormality, suggesting that the transplanted hepatocytes repopulated an irradiated liver and were metabolically functional. This strategy could be useful in the treatment of various genetic, metabolic, or malignant diseases of the liver.

Adenovirus-mediated antisense ATM gene transfer sensitizes prostate cancer cells to radiation.

Treatment failure after radiation therapy of prostate cancer (PC) could be a significant problem. Our objective is to design genetic radiosensitizing strategies for the treatment of PC. Cells from individuals with the genetic disorder ataxia telangiectasia (AT) are hypersensitive to ionizing radiation. Therefore, we examined whether attenuation of the AT gene product, AT mutated (ATM), in PC cells could result in an increased intrinsic radiosensitivity. A p53-mutant PC cell line, PC-3 was infected with adenoviral vectors, expressing antisense ATM RNA to various domains of the ATM gene. Immunoblot analyses of cellular extracts from antisense ATM-transfected PC-3 cells showed attenuated expression of the ATM protein within 2 days of viral infection. Compared with cells infected with an adeno-beta-galactosidase vector, antisense ATM-transfected PC-3 cells showed aberrant control of S-phase cell-cycle checkpoints after exposure to ionizing radiation. Under these conditions, the intrinsic radiosensitivity of the PC-3 cells was enhanced. Consequently antisense ATM gene therapy could serve as a paradigm for strategies that target the cellular survival mechanisms of an irradiated tumor cell and may provide therapeutic benefit to patients undergoing radiation therapy for PC.

Antisense ATM gene therapy: a strategy to increase the radiosensitivity of human tumors.

Atm, the gene mutated in ataxia-telangiectasia (AT) patients, is an essential component of the signal transduction pathway that responds to DNA damage due to ionizing radiation (IR). We attenuated ATM protein expression in human glioblastoma cells by expressing antisense RNA to a functional domain of the atm gene. While ATM expression decreased, constitutive expression of p53 and p21 increased. Irradiated ATM-attenuated cells failed to induce p53, demonstrated radioresistant DNA synthesis, and increased radiosensitivity. Antisense-ATM gene therapy in conjunction with radiation therapy may provide a novel strategy for the treatment of cancer.