Circulating Plasma Exosomal PD-L1 Predicts Prognosis of Head and Neck Squamous Cell Carcinoma After Radiation Therapy.

Purpose: Radiation therapy is widely used to treat head and neck squamous cell carcinoma (HNSCC). This study evaluated the association between circulating plasma programmed death-ligand 1 (PD-L1) and the outcomes of patients with HNSCC after radiation therapy. Methods and Materials: In this retrospective observational study, plasma samples of 76 patients with HNSCC who underwent radiation therapy from June 2019 to August 2021 were analyzed. These plasma samples were obtained before radiation therapy. The median follow-up was 32.5 months. Total and exosomal PD-L1 was measured by enzyme-linked immunosorbent assay and retrospectively analyzed for association with overall survival (OS), progression-free survival (PFS), and local control (LC). Prognostic factors among patients' characteristics and circulating PD-L1 in plasma were evaluated by univariate (log-rank test) and multivariate (Cox proportional hazards model) analyses. Results: The median concentration of total PD-L1 in plasma was 115.1 pg/mL (95% CI, 114.7-137.9 pg/mL), and the median concentration of exosomal PD-L1 was 2.8 pg/mL (95% CI, 6.0-13.0 pg/mL). Univariate and multivariate analyses showed exosomal PD-L1 as a prognostic factor for PFS and LC. Patients with high exosomal PD-L1 in plasma had poor PFS and LC compared with those with low exosomal PD-L1, indicating that 1-year PFS was 79.2% versus 33.3% (P < .001) and 1-year LC was 87.3% versus 50.0% (P < .001) in patients with high and low exosomal PD-L1, respectively. However, exosomal PD-L1 in plasma had no significant effect on OS. Total PD-L1 in plasma did not correlate with PFS, LC, and OS. Conclusions: The pretreatment circulating exosomal PD-L1 in plasma of patients with HNSCC was a prognostic factor after radiation therapy.

Irradiated Cell-derived Exosomes Enhance Cell Proliferation and Radioresistance via the MAPK/Erk Pathway.

BACKGROUND/AIM: Radiation therapy is pivotal in cancer treatment; however, its efficacy is limited by challenges such as tumor recurrence. This study delves into the role of exosomes, which are molecular cargo-bearing vesicles, in influencing cell proliferation, radioresistance, and consequent post-irradiation tumor recurrence. Given the significance of exosomes from irradiated malignancies in diagnostics and therapy, it is vital to delineate their functional dynamics, especially in breast and cervical cancer cell lines, where the impact of irradiation on exosome behavior remains enigmatic. MATERIALS AND METHODS: Using MDA-MB-231 and HeLa cell lines, exosomes were isolated from the culture supernatant via ultracentrifugation. The bicinchoninic acid assay was used to measure exosome quantities in irradiated and non-irradiated cells. Radiosensitivity was assessed using colony formation assays, while the role of the MAPK/Erk signaling pathway in recipient cell proliferation and radioresistance was probed using western blotting. RESULTS: Irradiated cells, in both MDA-MB-231 and HeLa lines, produced significantly more exosomes than their non-irradiated counterparts. Co-culturing irradiated cells with exosomes led to increased cell survival post-irradiation and enhanced cell proliferation in both cell lines. Western blotting indicated elevated p-Erk expression in such cells, underscoring the influence of the MAPK/Erk pathway in radioresistance and proliferation. CONCLUSION: The study establishes a potential nexus between exosome secretion and tumor resurgence following radiotherapy. The spotlight falls on the MAPK/ERK signaling conduit as a key influencer. This new knowledge provides an innovative strategy for counteracting cancer recurrence after radiotherapy, emphasizing the importance of understanding the multifaceted roles of exosomes in this context.

Exploring the Tumor-Suppressing Potential of PSCA in Pancreatic Ductal Adenocarcinoma.

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer with low survival rates. We explored an innovative therapeutic approach by leveraging prognostic oncogenic markers. Instead of inhibiting these marker genes, we harnessed their tumor-modifying potential in the extracellular domain. Surprisingly, many of the proteins highly expressed in PDAC, which is linked to poor survival, exhibited tumor-suppressing qualities in the extracellular environment. For instance, prostate stem cell antigens (PSCA), associated with reduced survival, acted as tumor suppressors when introduced extracellularly. We performed in vitro assays to assess the proliferation and migration and evaluated the tumor-modifying capacity of extracellular factors from peripheral blood mononuclear cells (PBMCs) in PDAC tissues. Molecular docking analysis, immunoprecipitation, Western blotting, and RNA interference were employed to study the regulatory mechanism. Extracellular PSCA recombinant protein notably curtailed the viability, motility, and transwell invasion of PDAC cells. Its anti-PDAC effects were partially mediated by Mesothelin (MSLN), another highly expressed tumor-associated antigen in PDAC. The anti-tumor effects of extracellular PSCA complemented those of chemotherapeutic agents like Irinotecan, 5-Fluorouracil, and Oxaliplatin. PSCA expression increased in a conditioned medium derived from PBMCs and T lymphocytes. This study unveils the paradoxical anti-PDAC potential of PSCA, hinting at the dual roles of oncoproteins like PSCA in PDAC suppression.

The impact of the COVID-19 pandemic on radiotherapy delivery in Japan: An observational study based on the national database.

BACKGROUND: This study analyzed the impact of the coronavirus disease 2019 (COVID-19) pandemic on radiotherapy delivery in Japan using a high-quality Japanese national database based on universal health coverage. METHODS: We performed a retrospective observational study using National Database of Health Insurance Claims and Specific Health Checkups of Japan open data focused on radiotherapy between fiscal year (FY) 2019 and FY2020 and the number of COVID-19 cases from the Ministry of Health, Labour, and Welfare. We statistically analyzed the relationship between the number of COVID-19 cases and the number of radiotherapy deliveries in Japan as a whole and by prefecture. RESULTS: The total number of external beam radiotherapy (EBRT) fractions was 4,472,140 in FY2019 and 4,227,673 in FY2020 (-5.8%). EBRT courses were 250,395 in FY2019 and 240,329 in FY2020 (-4.0%), stereotactic radiotherapy courses were 27,619 in FY2019 and 31,786 in FY2020 (+15.1%), and single-fraction palliative radiotherapy courses were 4124 in FY2019 and 5255 in FY2020 (+21.5%). The total number of breast and prostate hypofractionated radiotherapy (HFRT) fractions was 155,773 and 48,188 in FY2019, and 200,256 and 84,230 in FY2020 (+28.6% and +74.8%), respectively. In the Pearson correlation analysis, EBRT fractions were lower, and breast HFRT fractions were higher in prefectures with more COVID-19 cases. CONCLUSIONS: Overall, radiotherapy delivery in Japan was relatively stable after the pandemic, with an increase in HFRT. Also, EBRT fractions decreased, and breast HFRT were more likely to be used in prefectures with more COVID-19 cases.

The inhibition of pancreatic cancer progression by K-Ras-overexpressing mesenchymal stem cell-derived secretomes.

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer with poor survival. To explore an uncharted function of K-Ras proto-oncogene, K-Ras was activated in mesenchymal stem cells (MSCs) and the effects of MSC conditioned medium (CM) on PDAC were examined. Overexpression of K-Ras elevated PI3K signaling in MSCs, and K-Ras/PI3K-activated MSC-derived CM reduced the proliferation and migration of tumor cells, as well as the growth of ex vivo freshly isolated human PDAC cultures. CM's anti-tumor capability was additive with Gemcitabine, a commonly used chemotherapeutic drug in the treatment of PDAC. The systemic administration of CM in a mouse model suppressed the colonization of PDAC in the lung. MSC CM was enriched with Moesin (MSN), which acted as an extracellular tumor-suppressing protein by interacting with CD44. Tumor-suppressive CM was also generated by PKA-activated peripheral blood mononuclear cells. Collectively, this study demonstrated that MSC CM can be engineered to act as a tumor-suppressive agent by activating K-Ras and PI3K, and the MSN-CD44 regulatory axis is in part responsible for this potential unconventional option in the treatment of PDAC.

Suppression of osteosarcoma progression by engineered lymphocyte-derived proteomes.

Cancer cells tend to develop resistance to chemotherapy and enhance aggressiveness. A counterintuitive approach is to tame aggressiveness by an agent that acts opposite to chemotherapeutic agents. Based on this strategy, induced tumor-suppressing cells (iTSCs) have been generated from tumor cells and mesenchymal stem cells. Here, we examined the possibility of generating iTSCs from lymphocytes by activating PKA signaling for suppressing the progression of osteosarcoma (OS). While lymphocyte-derived CM did not present anti-tumor capabilities, the activation of PKA converted them into iTSCs. Inhibiting PKA conversely generated tumor-promotive secretomes. In a mouse model, PKA-activated CM suppressed tumor-induced bone destruction. Proteomics analysis revealed that moesin (MSN) and calreticulin (Calr), which are highly expressed intracellular proteins in many cancers, were enriched in PKA-activated CM, and they acted as extracellular tumor suppressors through CD44, CD47, and CD91. The study presented a unique option for cancer treatment by generating iTSCs that secret tumor-suppressive proteins such as MSN and Calr. We envision that identifying these tumor suppressors and predicting their binding partners such as CD44, which is an FDA-approved oncogenic target to be inhibited, may contribute to developing targeted protein therapy.

Increased toxicities associated with dose escalation of stereotactic body radiation therapy in prostate cancer: results from a phase I/II study.

BACKGROUND: This dose-escalation study evaluated the toxicity and efficacy of different stereotactic body radiation therapy (SBRT) doses for selecting an optimal dose for prostatic adenocarcinoma (PCa). MATERIALS AND METHODS: This clinical trial was registered at UMIN (UMIN000014328). Patients with low- or intermediate-risk PCa were equally assigned to 3 SBRT dose levels: 35, 37.5, and 40 Gy per 5 fractions. The primary endpoint was the occurrence rate of late grade ≥2 genitourinary (GU) and gastrointestinal (GI) adverse events at 2 years, while the secondary endpoint was the 2-year biochemical relapse-free (bRF) rate. Adverse events were evaluated using the Common Terminology Criteria for Adverse Events version 4.0. RESULTS: Seventy-five patients (median age, 70 years) were enrolled from March 2014 to January 2018, of whom 10 (15%) and 65 (85%) had low- and intermediate-risk PCa, respectively. The median follow-up time was 48 months. Twelve (16%) patients received neoadjuvant androgen deprivation therapy. The 2-year occurrence rates of grade 2 late GU and GI toxicities were 34 and 7% in all cohorts, respectively (35 Gy: 21 and 4%; 37.5 Gy: 40 and 14%; 40 Gy: 42 and 5%). The occurrence risk of GU toxicities significantly increased with dose escalation (p = 0.0256). Grades 2 and 3 acute GU toxicities were observed in 19 (25%) and 1 (1%), respectively. Grade 2 acute GI toxicity was observed in 8 (11%) patients. No grade ≥3 GI or ≥4 GU acute toxicity or grade ≥3 late toxicity was observed. Clinical recurrence was detected in 2 patients. CONCLUSIONS: An SBRT dose of 35 Gy per 5 fractions is less likely to cause adverse events in patients with PCa than 375- and 40-Gy SBRT doses. Higher doses of SBRT should be applied with caution.

Stereotactic ablative body radiotherapy with a central high dose using CyberKnife for metastatic lung tumors.

BACKGROUND: The CyberKnife system features a robotically-positioned linear accelerator to deliver real-time image-guided stereotactic ablative body radiotherapy (SABR). It achieves steep dose gradients using irradiation from hundreds of different directions and increases the central dose of the gross tumor volume (GTV) without increasing the marginal dose to the planning target volume. We evaluated the effectiveness and safety of SABR with a central high dose using CyberKnife for metastatic lung tumors. METHODS: A total of 73 patients with 112 metastatic lung tumors treated with CyberKnife were retrospectively analyzed. Local control, progression-free survival, and overall survival were calculated using the Kaplan-Meier method. The median age was 69.2 years. The most common primary sites were the uterus (n = 34), colorectum (n = 24), head and neck (n = 17), and esophagus (n = 16). For peripheral lung tumors, the median radiation dose was 52 Gy in 4 fractions, whereas for centrally located lung tumors, it was 60 Gy in 8-10 fractions. The dose prescription was defined as 99% of the solid tumor components of the GTV. The median maximum dose within the GTV was 61.0 Gy. The GTV and planning target volume were enclosed conformally by the 80% and 70% isodose lines of the maximum dose, respectively. The median follow-up period was extended to 24.7 months; it was 33.0 months for survivors. RESULTS: The 2-year local control, progression-free survival, and overall survival rates were 89.1%, 37.1%, and 71.3%, respectively. Toxicities of grade ≥ 2 were noted as grade 2 and 3 radiation pneumonitis in one patient each. The two patients with grade 2 or higher radiation pneumonitis had both received simultaneous irradiation at two or three metastatic lung tumor sites. No toxicity of grade ≥ 2 was observed in patients with metastasis in one lung only. CONCLUSIONS: SABR with a central high dose using CyberKnife for metastatic lung tumors is effective with acceptable toxicity. TRIAL REGISTRATION: Number: 20557, Name: Stereotactic ablative radiotherapy using CyberKnife for metastatic lung tumor, URL: http://www.radonc.med.osaka-u.ac.jp/pdf/SBRT.pdf , Date of registration: April 1, 2021 (retrospectively registered), Date of enrollment: May 1, 2014.

Proteomes from AMPK-inhibited peripheral blood mononuclear cells suppress the progression of breast cancer and bone metastasis.

Background: During a developmental process, embryos employ varying tactics to remove unwanted cells. Using a procedure analogous to some of the embryonic cells, we generated a tumor-eliminating conditioned medium (CM) from AMPK-inhibited lymphocytes and monocytes in peripheral blood mononuclear cells (PBMCs). Methods: AMPK signaling was inhibited by the application of a pharmacological agent, Dorsomorphin, and the therapeutic effects of their conditioned medium (CM) were evaluated using in vitro cell cultures, ex vivo breast cancer tissues, and a mouse model of mammary tumors and tumor-induced osteolysis. The regulatory mechanism was evaluated using mass spectrometry-based proteomics, Western blotting, immunoprecipitation, gene overexpression, and RNA interference. Results: While AMPK signaling acted mostly anti-tumorigenic, we paradoxically inhibited it to build induced tumor-suppressing cells and their tumor-eliminating CM. In a mouse model of breast cancer, the application of AMPK-inhibited lymphocyte-derived CM reduced mammary tumors additively to a chemotherapeutic agent, Taxol. It also prevented bone loss in the tumor-bearing tibia. Furthermore, the application of CM from the patient-derived peripheral blood diminished ex vivo breast cancer tissues isolated from the same patients. Notably, proteins enriched in CM included Moesin (MSN), Enolase 1 (ENO1), and polyA-binding protein 1 (PABPC1), which are considered tumorigenic in many types of cancer. The tumor-suppressing actions of MSN and ENO1 were at least in part mediated by Metadherin (Mtdh), which is known to promote metastatic seeding. Conclusion: We demonstrated that PBMCs can be used to generate tumor-suppressive proteomes, and extracellular tumor-suppressing proteins such as MSN, ENO1, and PABPC1 are converted from tumor-promoting factors inside cancer cells. The results support the possibility of developing autologous blood-based therapy, in which tumor-suppressing proteins are enriched in engineered PBMC-derived CM by the inhibition of AMPK signaling.

The impact of the COVID-19 pandemic on radiotherapy in Japan: nationwide surveys from May 2020 through June 2021.

A longitudinal online questionnaire survey on the impact of coronavirus disease 2019 (COVID-19) on the operation of radiotherapy departments in Japan was conducted. Approximately 26.1-70.9% of the radiotherapy departments participated, and their responses were collected in May, July and November 2020, and February and June 2021. The survey results revealed that while the number of patients receiving radiotherapy decreased in 41.2% and 30.7% of institutions in May 2020 and June 2021, respectively, it increased in 4% and 16.8% of institutions in May 2020 and June 2021, respectively. There were a few institutions limiting or postponing patient treatments in June 2021. The hypofractionated regimen was used more during the pandemic than during the pre-pandemic period, particularly for the treatment of breast and prostate cancers as well as for palliation. Infection control measures for patients and staff were followed. Approximately 20% of the respondent institutions had cases of patients with COVID-19 infection receiving radiotherapy. Most institutions encountered challenges in the continuous provision of radiotherapy for patients with COVID-19. In conclusion, COVID-19 had a multifaceted impact on the operations of radiotherapy departments in Japan. Further follow-up and analysis are warranted to understand the long-term impact of COVID-19 on radiotherapy.

COVID-19 vaccine-induced Recurrence of the Radiation Recall Phenomenon in the Laryngeal Mucosa Due to a VEGF Inhibitor.

Purpose: The radiation recall phenomenon (RRP) is a rare and unexpected late complication of radiation therapy (RT). Although predominantly in the skin, RRP of the upper respiratory tract has also been reported. In general, RRP is caused by anticancer agents, and the COVID-19 vaccine has also been reported to cause RRP in recent years. Methods and Materials: A 50-year-old woman who had received RT around the larynx 3 years prior and was receiving a docetaxel + ramucirumab (RAM) regimen experienced recurrent sore throat. The administration of RAM was discontinued after a gastroscopic examination revealed mucosal bleeding from around the larynx, which was thought to be RRP caused by RAM, a vascular endothelial growth factor inhibitor. Results: After the remission of the RRP, the patient received a COVID-19 vaccine (Pfizer-BioNTech). Five days later, the appearance of cough and recurrence of sore throat worsened with time, and marked stridor was observed. The patient was admitted, and steroid pulse therapy was administered for 3 days starting on day 18 after vaccination. On day 50 after vaccination, edema of the vocal cords improved. Conclusions: When administering COVID-19 vaccines, considering that these vaccines may cause RRP is important, because RRP can be fatal in patients with a history of RT in the laryngeal region and treated with vascular endothelial growth factor inhibitors.

Long-term Outcomes of Radiation Therapy for Prostate Cancer in Elderly Patients Aged ≥75 Years.

BACKGROUND/AIM: This study aimed to evaluate the treatment outcomes of radiation therapy (RT) for localized prostate cancer in elderly patients aged ≥75 years. PATIENTS AND METHODS: We retrospectively investigated data of patients aged ≥75 years with prostate cancer who underwent intensity-modulated radiation therapy (IMRT) or volumetric modulated arc therapy (VMAT) with doses of 70-78 Gy in 35-39 fractions between September 2008 and June 2016. Overall survival (OS), recurrence-free (RF) rates, and occurrence rates of toxicities were calculated. RESULTS: Eighty-eight patients were enrolled in the study. Nineteen patients died, and nine patients reported PSA failure within the follow-up period. The median follow-up time was 83.5 months. The median age was 77 years. In the cohort, 6 were low-risk, 36 were intermediaterisk, and 46 were high-risk patients. The 5-/7-year OS and RF rates were 87.9%/80.2% and 93.5%/89.1%, respectively. By risk, the 5-/7-year RF rates were 100%/80% in the low-, 100%/100% in the intermediate-, and 87.6%/82.7% in the high-risk groups, respectively. The cumulative incidence rates of Grade ≥3 genitourinary and gastrointestinal toxicities were 1.3% and 3.5% at 5 years and 3.3% and 3.5% at 7 years, respectively. CONCLUSION: IMRT and VMAT are effective treatment options for elderly patients with prostate cancer and in a good general condition.

Radiation therapy enhances systemic antitumor efficacy in PD-L1 therapy regardless of sequence of radiation in murine osteosarcoma.

Recent studies demonstrate that immune checkpoint blockade (ICB) increases the chances of the abscopal effect, an anti-tumor effect outside the radiation field in radiation therapy. However, the optimal sequence between radiation and ICB remains unclear. To investigate the impact of sequence of radiation in anti-PD-L1 antibody (P1) therapy on immune microenvironments and antitumor efficacies in local and abscopal tumors, metastatic LM8 osteosarcoma cells were inoculated into both legs of C3H mice. For irradiation, only one side leg was irradiated at 10 Gy. Then mice were divided into four groups: administrated anti-PD-L1 antibody three times (P1 monotherapy), receiving radiation 3 days prior to P1 therapy (P1+pre-Rad), and receiving concurrent radiation with P1 therapy (P1+conc-Rad). Thereafter, tumor immune microenvironment and tumor volume changes were analyzed in irradiated and unirradiated tumors. The P1+pre-Rad regimen increased the proportion of CD8+ programmed cell death 1 (PD-1)+ granzyme B (GzmB)+ reinvigorated T cells and decreased the proportion of CD8+ PD-1+ GzmB- exhausted T cells than P1+conc-Rad regimen in unirradiated tumors. Combination regimens suppressed tumor growth in irradiated tumors compared with that in P1 monotherapy. In both irradiated and unirradiated tumors, significant tumor growth suppression and prolonged overall survival were observed under both combination treatment regimens compared with P1 monotherapy. However, no distinct differences in unirradiated tumor volume and survival were observed between P1+pre-Rad and P1+conc-Rad groups. These results suggest that local irradiation is necessary to improve systemic treatment efficacy in P1 therapy regardless of sequence of local irradiation.

N(6)-methyladenosine methylation-regulated polo-like kinase 1 cell cycle homeostasis as a potential target of radiotherapy in pancreatic adenocarcinoma.

In pancreatic cancer, methyltransferase-like 3 (METTL3), a N(6)-methyladenosine (m6A) methyltransferase, has a favorable effect on tumors and is a risk factor for patients' prognosis. However, the details of what genes are regulated by METTL3 remain unknown. Several RNAs are methylated, and what genes are favored in pancreatic cancer remains unclear. By epitranscriptomic analysis, we report that polo-like kinase 1 (PLK1) is an important hub gene defining patient prognosis in pancreatic cancer and that RNA methylation is involved in regulating its cell cycle-specific expression. We found that insulin like growth factor 2 mRNA binding protein 2 (IGF2BP2) binds to m6A of PLK1 3' untranslated region and is involved in upregulating PLK1 expression and that demethylation of this site activates the ataxia telangiectasia and Rad3-related protein pathway by replicating stress and increasing mitotic catastrophe, resulting in increased radiosensitivity. This suggests that PLK1 methylation is essential for cell cycle maintenance in pancreatic cancer and is a new therapeutic target.

High Dose Local Photon Irradiation Is Crucial in Anti-CTLA-4 Antibody Therapy to Enhance the Abscopal Response in a Murine Pancreatic Carcinoma Model.

Pancreatic cancer is an extremely treatment-resistant neoplasm to chemotherapy and immunotherapy. The combination of photon beam irradiation and anti-CTLA-4 antibody (C4) for the anti-tumor effect enhancement at local and distant tumors (abscopal tumors) was investigated using the pancreatic ductal adenocarcinoma (PDAC) mouse model. Pan02 cells were bilaterally inoculated to both legs of C57BL/6 mice. High dose photon beams in a hypofractionation or a single fraction were delivered to the tumors on one leg. Monotherapy with C4 via i.p. was not effective for PDAC. The high dose irradiation to the local tumors produced significant shrinkage of irradiated tumors but did not induce the abscopal responses. In contrast, the combination therapy of high dose photon beam irradiation in both hypofractionation and a single fraction with C4 enhanced the anti-tumor effect for abscopal tumors with significantly prolonged overall survival. The flow cytometric analysis revealed that the combination therapy dramatically decreased the regulatory T cell (Treg) proportion while increasing the cytotoxic T lymphocytes in both local and abscopal tumors. These results suggest that high dose photon beam irradiation plays an important role in C4 therapy to enhance the abscopal response with immune microenvironment changes in PDAC, regardless of the fractionation in radiation therapy.

Poly (ADP-ribose) polymerase inhibitors sensitize cancer cells to hypofractionated radiotherapy through altered selection of DNA double-strand break repair pathways.

PURPOSE: Poly (ADP-ribose) polymerase inhibitors (PARPi) are known to induce radiosensitization. However, the exact mechanisms of radiosensitization remain unclear. We previously reported that PARPi may have a unique radiosensitizing effect to enhance ß-components of the linear-quadratic model. The aim of this study was to evaluate PARPi in combination with high-dose-per-fraction radiotherapy and to elucidate the underlying mechanisms of its radiosensitization. MATERIALS AND METHODS: Radiosensitizing effects of PARPi PJ34, olaparib, and veliparib were measured using a colony-forming assay in the human cancer cell lines, HCT116, NCI-H460, and HT29. Six different radiation dose fractionation schedules were examined by tumor regrowth assay using three-dimensional multicellular spheroids of HCT116, NCI-H460, SW620, and HCT15. The mechanisms of radiosensitization were analyzed by measuring DNA double-strand breaks (DSB), DNA damage responses, chromosomal translocations, cellular senescence, and cell cycle analysis. RESULTS: Olaparib and PJ34 were found to show radiosensitization preferentially at higher radiation doses per fraction. Similar results were obtained using a mouse model bearing human tumor xenografts. A kinetic analysis of DNA damage responses and repairs showed that olaparib and PJ34 reduced the homologous recombination activity. However, a neutral comet assay showed that PJ34 treatment did not affect the physical rejoining of DNA-DSBs induced by ionizing radiation. Cell cycle analysis revealed that olaparib and PJ34 strikingly increased G1 tetraploid cells following irradiation, leading to premature senescence. The C-banding analysis of metaphase spreads showed that olaparib and PJ34 significantly increased ionizing radiation-induced dicentric chromosomes. The data suggests that PARPi olaparib and PJ34 altered the choice of DNA-DSB repair pathways rather than reducing the total amount of DNA-DSB repair, which resulted in increased repair errors. Increased quadratic misrepair was one of the mechanisms of PARP-mediated radiosensitization, preferentially at the higher dose range compared to the lower dose range. CONCLUSION: PARPi may be a promising candidate to combine with stereotactic hypofractionated radiotherapy, aiming at high-dose region-directed radiosensitization.

Stereotactic Ablative Radiotherapy Using CyberKnife for Stage I Non-small-cell Lung Cancer: A Retrospective Analysis.

BACKGROUND/AIM: We evaluated the effectiveness and safety of stereotactic ablative radiotherapy (SABR) delivered using Cyberknife in patients with stage I non-small-cell lung cancer. PATIENTS AND METHODS: The clinical results of 153 patients with 161 lung cancers treated with CyberKnife between May 2014 and August 2020 at the Osaka University Hospital were retrospectively analyzed. The median age was 80 years (range=48-99 years). Nine patients (5.6%) had interstitial pneumonia. The median radiation dose was 52 Gy (range=40-70 Gy) in 4-10 fractions, and the median follow-up extended to 21.4 months (range=0-68.9 months). RESULTS: The 2-year local control, progression-free, and overall survival rates were 91.9%, 61.7%, and 84.8%, respectively. Toxicities of grade ≥3 were observed in 13 (8.1%) patients; one patient with interstitial pneumonia developed grade 5 radiation pneumonitis and one patient developed grade 5 bronchopulmonary hemorrhage. CONCLUSION: In patients with stage I non-small-cell lung cancer, SABR using Cyberknife was effective with acceptable toxicity.

Methylosystem for Cancer Sieging Strategy.

As cancer is a genetic disease, methylation defines a biologically malignant phenotype of cancer in the association of one-carbon metabolism-dependent S-adenosylmethionine (SAM) as a methyl donor in each cell. Methylated substances are involved in intracellular metabolism, but via intercellular communication, some of these can also be secreted to affect other substances. Although metabolic analysis at the single-cell level remains challenging, studying the "methylosystem" (i.e., the intercellular and intracellular communications of upstream regulatory factors and/or downstream effectors that affect the epigenetic mechanism involving the transfer of a methyl group from SAM onto the specific positions of nucleotides or other metabolites in the tumor microenvironment) and tracking these metabolic products are important research tasks for understanding spatial heterogeneity. Here, we discuss and highlight the involvement of RNA and nicotinamide, recently emerged targets, in SAM-producing one-carbon metabolism in cancer cells, cancer-associated fibroblasts, and immune cells. Their significance and implications will contribute to the discovery of efficient methods for the diagnosis of and therapeutic approaches to human cancer.

Characteristics of microSilicon diode detector for electron beam dosimetry.

A microSilicon™ (PTW type 60023), a new unshielded diode detector succeeding Diode E (model 60017, PTW), was characterized for electron beam dosimetry and compared with other detectors. Electron beams generated from a TrueBeam linear accelerator were measured using the microSilicon, Diode E, and microDiamond synthetic single-crystal diamond detector. Positional accuracy of microSilicon was measured by data collected in air and water. The percent depth dose (PDD), off-center ratio (OCR), dose-response linearity, dose rate dependence, and cone factors were evaluated. The PDDs were compared with data measured using a PPC40 plane-parallel ionization chamber. The maximum variations of depth of 50% and 90% of the maximum dose, and practical depth among all detectors and energies were 0.9 mm. The maximum variations of the bremsstrahlung dose among all detectors and energies were within 0.3%. OCR showed good agreement within 1% for the flat and tail regions. The microSilicon detector showed a penumbra width similar to microDiamond, whereas Diode E showed the steepest penumbra shape. All detectors showed good dose-response linearity and stability against the dose rate; only Diode E demonstrated logarithmic dose rate dependency. The cone factor measured with microSilicon was within ±1% for all energies and cone sizes. We demonstrated that the characteristics of microSilicon is suitable for electron beam dosimetry. The microSilicon detector can be a good alternative for electron beam dosimetry in terms of providing an appropriate PDD curve without corrections, high spatial resolution for OCR measurements and cone factors.