A retrospective study on the investigation of potential dosimetric benefits of online adaptive proton therapy for head and neck cancer

PURPOSE

Proton therapy is sensitive to anatomical changes, often occurring in head-and-neck (HN) cancer patients. Although multiple studies have proposed online adaptive proton therapy (APT), there is still a concern in the radiotherapy community about the necessity of online APT. We have performed a retrospective study to investigate the potential dosimetric benefits of online APT for HN patients relative to the current offline APT.

METHODS

Our retrospective study has a patient cohort of 10 cases. To mimic online APT, we re-evaluated the dose of the in-use treatment plan on patients' actual treatment anatomy captured by cone-beam CT (CBCT) for each fraction and performed a templated-based automatic replanning if needed, assuming that these were performed online before treatment delivery. Cumulative dose of the simulated online APT course was calculated and compared with that of the actual offline APT course and the designed plan dose of the initial treatment plan (referred to as nominal plan). The ProKnow scoring system was employed and adapted for our study to quantify the actual quality of both courses against our planning goals.

RESULTS

The average score of the nominal plans over the 10 cases is 41.0, while those of the actual offline APT course and our simulated online course is 25.8 and 37.5, respectively. Compared to the offline APT course, our online course improved dose quality for all cases, with the score improvement ranging from 0.4 to 26.9 and an average improvement of 11.7.

CONCLUSION

The results of our retrospective study have demonstrated that online APT can better address anatomical changes for HN cancer patients than the current offline replanning practice. The advanced artificial intelligence based automatic replanning technology presents a promising avenue for extending potential benefits of online APT.

Streamlined pin-ridge-filter design for single-energy proton FLASH planning

BACKGROUND

FLASH radiotherapy (FLASH-RT) with ultra-high dose rate has yielded promising results in reducing normal tissue toxicity while maintaining tumor control. Planning with single-energy proton beams modulated by ridge filters (RFs) has been demonstrated feasible for FLASH-RT.

PURPOSE

This study explored the feasibility of a streamlined pin-shaped RF (pin-RF) design, characterized by coarse resolution and sparsely distributed ridge pins, for single-energy proton FLASH planning.

METHODS

An inverse planning framework integrated within a treatment planning system was established to design streamlined pin RFs for single-energy FLASH planning. The framework involves generating a multi-energy proton beam plan using intensity-modulated proton therapy (IMPT) planning based on downstream energy modulation strategy (IMPT-DS), followed by a nested pencil-beam-direction-based (PBD-based) spot reduction process to iteratively reduce the total number of PBDs and energy layers along each PBD for the IMPT-DS plan. The IMPT-DS plan is then translated into the pin-RFs and the single-energy beam configurations for IMPT planning with pin-RFs (IMPT-RF). This framework was validated on three lung cases, quantifying the FLASH dose of the IMPT-RF plan using the FLASH effectiveness model. The FLASH dose was then compared to the reference dose of a conventional IMPT plan to measure the clinical benefit of the FLASH planning technique.

RESULTS

The IMPT-RF plans closely matched the corresponding IMPT-DS plans in high dose conformity (conformity index of <1.2), with minimal changes in V7Gy and V7.4 Gy for the lung (<3%) and small increases in maximum doses (Dmax) for other normal structures (<3.4 Gy). Comparing the FLASH doses to the doses of corresponding IMPT-RF plans, drastic reductions of up to nearly 33% were observed in Dmax for the normal structures situated in the high-to-moderate-dose regions, while negligible changes were found in Dmax for normal structures in low-dose regions. Positive clinical benefits were seen in comparing the FLASH doses to the reference doses, with notable reductions of 21.4%-33.0% in Dmax for healthy tissues in the high-dose regions. However, in the moderate-to-low-dose regions, only marginal positive or even negative clinical benefit for normal tissues were observed, such as increased lung V7Gy and V7.4 Gy (up to 17.6%).

CONCLUSIONS

A streamlined pin-RF design was developed and its effectiveness for single-energy proton FLASH planning was validated, revealing positive clinical benefits for the normal tissues in the high dose regions. The coarsened design of the pin-RF demonstrates potential advantages, including cost efficiency and ease of adjustability, making it a promising option for efficient production.

Synthetic CT generation from MRI using 3D transformer-based denoising diffusion model

BACKGROUND AND PURPOSE

Magnetic resonance imaging (MRI)-based synthetic computed tomography (sCT) simplifies radiation therapy treatment planning by eliminating the need for CT simulation and error-prone image registration, ultimately reducing patient radiation dose and setup uncertainty. In this work, we propose a MRI-to-CT transformer-based improved denoising diffusion probabilistic model (MC-IDDPM) to translate MRI into high-quality sCT to facilitate radiation treatment planning.

METHODS

MC-IDDPM implements diffusion processes with a shifted-window transformer network to generate sCT from MRI. The proposed model consists of two processes: a forward process, which involves adding Gaussian noise to real CT scans to create noisy images, and a reverse process, in which a shifted-window transformer V-net (Swin-Vnet) denoises the noisy CT scans conditioned on the MRI from the same patient to produce noise-free CT scans. With an optimally trained Swin-Vnet, the reverse diffusion process was used to generate noise-free sCT scans matching MRI anatomy. We evaluated the proposed method by generating sCT from MRI on an institutional brain dataset and an institutional prostate dataset. Quantitative evaluations were conducted using several metrics, including Mean Absolute Error (MAE), Peak Signal-to-Noise Ratio (PSNR), Multi-scale Structure Similarity Index (SSIM), and Normalized Cross Correlation (NCC). Dosimetry analyses were also performed, including comparisons of mean dose and target dose coverages for 95% and 99%.

RESULTS

MC-IDDPM generated brain sCTs with state-of-the-art quantitative results with MAE 48.825 ± 21.491 HU, PSNR 26.491 ± 2.814 dB, SSIM 0.947 ± 0.032, and NCC 0.976 ± 0.019. For the prostate dataset: MAE 55.124 ± 9.414 HU, PSNR 28.708 ± 2.112 dB, SSIM 0.878 ± 0.040, and NCC 0.940 ± 0.039. MC-IDDPM demonstrates a statistically significant improvement (with p < 0.05) in most metrics when compared to competing networks, for both brain and prostate synthetic CT. Dosimetry analyses indicated that the target dose coverage differences by using CT and sCT were within ± 0.34%.

CONCLUSIONS

We have developed and validated a novel approach for generating CT images from routine MRIs using a transformer-based improved DDPM. This model effectively captures the complex relationship between CT and MRI images, allowing for robust and high-quality synthetic CT images to be generated in a matter of minutes. This approach has the potential to greatly simplify the treatment planning process for radiation therapy by eliminating the need for additional CT scans, reducing the amount of time patients spend in treatment planning, and enhancing the accuracy of treatment delivery.

Radiation and anti-PD-L1 synergize by stimulating a stem-like T cell population in the tumor-draining lymph node

Radiotherapy (RT) and anti-PD-L1 synergize to enhance local and distant (abscopal) tumor control. However, clinical results in humans have been variable. With the goal of improving clinical outcomes, we investigated the underlying synergistic mechanism focusing on a CD8+ PD-1+ Tcf-1+ stem-like T cell subset in the tumor-draining lymph node (TdLN). Using murine melanoma models, we found that RT + anti-PD-L1 induces a novel differentiation program in the TdLN stem-like population which leads to their expansion and differentiation into effector cells within the tumor. Our data indicate that optimal synergy between RT + anti-PD-L1 is dependent on the TdLN stem-like T cell population as either blockade of TdLN egress or specific stem-like T cell depletion reduced tumor control. Together, these data demonstrate a multistep stimulation of stem-like T cells following combination therapy which is initiated in the TdLN and completed in the tumor.

ATR signaling controls the bystander responses of human chondrosarcoma cells by promoting RAD51-dependent DNA repair

PURPOSE

Radiation-induced bystander effect (RIBE) frequently is seen as DNA damage in unirradiated bystander cells, but the repair processes initiated in response to that DNA damage are not well understood. RIBE-mediated formation of micronuclei (MN), a biomarker of persistent DNA damage, was previously observed in bystander normal fibroblast (AG01522) cells, but not in bystander human chondrosarcoma (HTB94) cells. The molecular mechanisms causing this disparity are not clear. Herein, we investigate the role of DNA repair in the bystander responses of the two cell lines.

METHODS

Cells were irradiated with X-rays and immediately co-cultured with un-irradiated cells using a trans-well insert system in which they share the same medium. The activation of DNA damage response (DDR) proteins was detected by immunofluorescence staining or Western blotting. MN formation was examined by the cytokinesis-block MN assay, which is a robust method to detect persistent DNA damage.

RESULTS

Immunofluorescent foci of γH2AX and 53BP1, biomarkers of DNA damage and repair, revealed a greater capacity for DNA repair in HTB94 cells than in AG01522 cells in both irradiated and bystander populations. Autophosphorylation of ATR at the threonine 1989 site was expressed at a greater level in HTB94 cells compared to AG01522 cells at the baseline and in response to hydroxyurea treatment or exposure to 1 Gy of X-rays. An inhibitor of ATR, but not of ATM, promoted MN formation in bystander HTB94 cells. In contrast, no effect of either inhibitor was observed in bystander AG01522 cells, indicating that ATR signaling might be a pivotal pathway to preventing the MN formation in bystander HTB94 cells. Supporting this idea, we found an ATR-dependent increase in the fractions of bystander HTB94 cells with pRPA2 S33 and RAD51 foci. A blocker of RAD51 facilitated MN formation in bystander HTB94 cells.

CONCLUSION

Our results indicate that HTB94 cells were likely more efficient in DNA repair than AG01522 cells, specifically via ATR signaling, which inhibited the bystander signal-induced MN formation. This study highlights the significance of DNA repair efficiency in bystander cell responses.

CBCT-Based synthetic CT image generation using conditional denoising diffusion probabilistic model

BACKGROUND

Daily or weekly cone-beam computed tomography (CBCT) scans are commonly used for accurate patient positioning during the image-guided radiotherapy (IGRT) process, making it an ideal option for adaptive radiotherapy (ART) replanning. However, the presence of severe artifacts and inaccurate Hounsfield unit (HU) values prevent its use for quantitative applications such as organ segmentation and dose calculation. To enable the clinical practice of online ART, it is crucial to obtain CBCT scans with a quality comparable to that of a CT scan.

PURPOSE

This work aims to develop a conditional diffusion model to perform image translation from the CBCT to the CT distribution for the image quality improvement of CBCT.

METHODS

The proposed method is a conditional denoising diffusion probabilistic model (DDPM) that utilizes a time-embedded U-net architecture with residual and attention blocks to gradually transform the white Gaussian noise sample to the target CT distribution conditioned on the CBCT. The model was trained on deformed planning CT (dpCT) and CBCT image pairs, and its feasibility was verified in brain patient study and head-and-neck (H&N) patient study. The performance of the proposed algorithm was evaluated using mean absolute error (MAE), peak signal-to-noise ratio (PSNR) and normalized cross-correlation (NCC) metrics on generated synthetic CT (sCT) samples. The proposed method was also compared to four other diffusion model-based sCT generation methods.

RESULTS

In the brain patient study, the MAE, PSNR, and NCC of the generated sCT were 25.99 HU, 30.49 dB, and 0.99, respectively, compared to 40.63 HU, 27.87 dB, and 0.98 of the CBCT images. In the H&N patient study, the metrics were 32.56 HU, 27.65 dB, 0.98 and 38.99 HU, 27.00, 0.98 for sCT and CBCT, respectively. Compared to the other four diffusion models and one Cycle generative adversarial network (Cycle GAN), the proposed method showed superior results in both visual quality and quantitative analysis.

CONCLUSIONS

The proposed conditional DDPM method can generate sCT from CBCT with accurate HU numbers and reduced artifacts, enabling accurate CBCT-based organ segmentation and dose calculation for online ART.

[Epidemiological characteristics of human respiratory syncytial virus (HRSV) among acute respiratory infection (ARI) cases in 16 provinces of China from 2009 to 2023]

Objective: To understand the epidemiological characteristics of human respiratory syncytial virus (HRSV) among acute respiratory infection (ARI) cases in 16 provinces of China from 2009 to 2023. Methods: The data of this study were collected from the ARI surveillance data from 16 provinces in China from 2009 to 2023, with a total of 28 278 ARI cases included in the study. The clinical specimens from ARI cases were screened for HRSV nucleic acid from 2009 to 2023, and differences in virus detection rates among cases of different age groups, regions, and months were analyzed. Results: A total of 28 278 ARI cases were enrolled from January 2009 to September 2023. The age of the cases ranged from<1 month to 112 years, and the age M (Q1, Q3) was 3 years (1 year, 9 years). Among them, 3 062 cases were positive for HRSV nucleic acid, with a total detection rate of 10.83%. From 2009 to 2019, the detection rate of HRSV was 9.33%, and the virus was mainly prevalent in winter and spring. During the Corona Virus Disease 2019 (COVID-19) pandemic, the detection rate of HRSV fluctuated between 6.32% and 18.67%. There was no traditional winter epidemic peak of HRSV from the end of 2022 to the beginning of 2023, and an anti-seasonal epidemic of HRSV occurred from April to May 2023. About 87.95% (2 693/3 062) of positive cases were children under 5 years old, and the difference in the detection rate of HRSV among different age groups was statistically significant (P<0.001), showing a decreasing trend of HRSV detection rate with the increase of age (P<0.001). Among them, the HRSV detection rate (25.69%) was highest in children under 6 months. Compared with 2009-2019, the ranking of HRSV detection rates in different age groups changed from high to low between 2020 and 2023, with the age M (Q1, Q3) of HRSV positive cases increasing from 1 year (6 months, 3 years) to 2 years (11 months, 3 years). Conclusion: Through 15 years of continuous HRSV surveillance analysis, children under 5 years old, especially infants under 6 months old, are the main high-risk population for HRSV infection. During the COVID-19 pandemic, the prevalence and patterns of HRSV in China have changed.

The putative RNA helicase DDX1 associates with the nuclear RNA exosome and modulates RNA/DNA hybrids (R-loops)

The RNA exosome is a ribonuclease complex that mediates both RNA processing and degradation. This complex is evolutionarily conserved, ubiquitously expressed, and required for fundamental cellular functions, including rRNA processing. The RNA exosome plays roles in regulating gene expression and protecting the genome, including modulating the accumulation of RNA-DNA hybrids (R-loops). The function of the RNA exosome is facilitated by cofactors, such as the RNA helicase MTR4, which binds/remodels RNAs. Recently, missense mutations in RNA exosome subunit genes have been linked to neurological diseases. One possibility to explain why missense mutations in genes encoding RNA exosome subunits lead to neurological diseases is that the complex may interact with cell- or tissue-specific cofactors that are impacted by these changes. To begin addressing this question, we performed immunoprecipitation of the RNA exosome subunit, EXOSC3, in a neuronal cell line (N2A), followed by proteomic analyses to identify novel interactors. We identified the putative RNA helicase, DDX1, as an interactor. DDX1 plays roles in double-strand break repair, rRNA processing, and R-loop modulation. To explore the functional connections between EXOSC3 and DDX1, we examined the interaction following double-strand breaks and analyzed changes in R-loops in N2A cells depleted for EXOSC3 or DDX1 by DNA/RNA immunoprecipitation followed by sequencing. We find that EXOSC3 interaction with DDX1 is decreased in the presence of DNA damage and that loss of EXOSC3 or DDX1 alters R-loops. These results suggest EXOSC3 and DDX1 interact during events of cellular homeostasis and potentially suppress unscrupulous expression of genes promoting neuronal projection.

HELZ promotes R loop resolution to facilitate DNA double-strand break repair by homologous recombination

R loops are RNA-DNA hybrid containing structures involved in diverse cellular processes, including DNA double-strand break (DSB) repair. R loop homeostasis involving the formation and resolution of R loops is critical for DSB repair, and its dysregulation leads to genome instability. Here we show that the HELZ helicase promotes R loop resolution to facilitate DSB repair by homologous recombination (HR). HELZ depletion causes hypersensitivity to DSB-inducing agents, and HELZ localizes and binds to DSBs. HELZ depletion further leads to genomic instability in a R loop dependent manner and the accumulation of R loops globally and at DSBs. HELZ binds to R loops in response to DSBs and promotes their resolution, thereby facilitating HR to promote genome integrity. Our findings thus define a role for HELZ in promoting the resolution of R loops critical for DSB repair by HR.

Streamlined Pin-Ridge-Filter Design for Single-energy Proton FLASH Planning

PURPOSE

This study explored the feasibility of a streamlined pin-shaped ridge filter (pin-RF) design for single-energy proton FLASH planning.

METHODS

An inverse planning framework integrated within a TPS was established for FLASH planning. The framework involves generating a IMPT plan based on downstream energy modulation strategy (IMPT-DS), followed by a nested spot reduction process to iteratively reduce the total number of pencil beam directions (PBDs) and energy layers along each PBD for the IMPT-DS plan. The IMPT-DS plan is then translated into the pin-RFs for a single-energy IMPT plan (IMPT-RF). The framework was validated on three lung cases, quantifying the FLASH dose of the IMPT-RF plan using the FLASH effectiveness model and comparing it with the reference dose of a conventional IMPT plan to assess the clinical benefit of the FLASH planning technique.

RESULTS

The IMPT-RF plans closely matched the corresponding IMPT-DS plans in high dose conformity, with minimal changes in V7Gy and V7.4Gy for the lung (< 5%) and small increases in Dmax for other OARs (< 3.2 Gy). Comparing the FLASH doses to the doses of corresponding IMPT-RF plans, drastic reductions of up to ~33% were observed in Dmax for OARs in the high-to-moderate-dose regions with negligible changes in Dmax for OARs in low-dose regions. Positive clinical benefits were observed with notable reductions of 18.4-33.0% in Dmax for OARs in the high-dose regions. However, in the moderate-to-low-dose regions, only marginal positive or even negative clinical benefit for OARs were observed, such as increased lung V7Gy and V7.4Gy (16.4-38.9%).

CONCLUSIONS

A streamlined pin-RF design for single-energy proton FLASH planning was validated, revealing positive clinical benefits for OARs in the high dose regions. The coarsened design of the pin-RF demonstrates potential cost efficiency and efficient production.

Estimating Potential Benefits of Online Adaptive Proton Therapy for Head-and-Neck Cancer: A Retrospective Study

PURPOSE/OBJECTIVE(S)

Proton therapy is highly sensitive to anatomical changes and setup variations in head-and-neck (HN) treatments. To address this issue, proton centers often acquire patient CT images weekly to monitor patient anatomical changes during the treatment course and perform offline plan adaptation when needed. However, offline adaptation cannot fully account for daily setup variations or the anatomical changes occurring with high frequency. There are a few groups endeavoring to develop advanced technologies to enable online adaptive proton therapy (APT). However, the necessity of online APT remains controversial, as it is unknown that whether online APT will significantly improve treatment quality and outcomes compared to offline APT. The purpose of this study is to estimate the clinical potential of online APT in the management of HN cancers in relation to the current offline APT.

MATERIALS/METHODS

Our retrospective study was conducted with four HN patients (35 fractions per patient), who had been treated with intensity modulated proton therapy and had offline adaptation once or twice during their treatment courses. Synthetic CT (sCT) images were generated from 140 daily CBCT images for us to recalculate the dose of the treatment plan in patient's actual treatment anatomy for each treatment fraction and adapt the plan when warranted. These adaptations were assumed to be performed online before treatment delivery to mimic an online APT course. Accumulative doses were calculated for both courses using the CBCT-based sCT images of every fraction for us to compare the target coverage, organ at risk (OAR) sparing, tumor control probability (TCP) and normal tissue complication probability (NTCP). An in-house script was developed to semi-automate this process in a commercial treatment planning system to facilitate our study.

RESULTS

All patients would benefit from online APT to different extents. For the first patient, with OAR doses comparable to the actual offline course, the retrospective online APT course improved dose coverages of the three CTVs from 95.2%, 98.64% and 89.53% to 98.88%, 99.81%, 98.97%, which would lead to a 4.52% improvement in TCP. Similarly, online APT would yield a 2.66% improvement in TCP for the second patient. For the third patient, with comparable CTV dose coverages, the mean doses of right parotid and oral cavity were decreased from 29.52 Gy relative biological effectiveness (RBE) and 41.89 Gy RBE to 22.16 Gy RBE and 34.61 Gy RBE, leading to a reduce of 1.67% and 3.40% in NTCP. The mean dose of right parotid was decreased from 21.71 Gy RBE to 19.37 Gy RBE for the last patient, leading to a reduce of 0.73% in NTCP.

CONCLUSION

Our results showed that online APT could better maintain the treatment plan quality than offline APT for all the four patients, despite their significant anatomical changes. Future investigation will focus on collecting more patient data to obtain statistically significant results and help identify the patients to whom the online APT will be of most benefit.

YB1 modulates the DNA damage response in medulloblastoma

Y-box binding protein 1 (YBX1 or YB1) is a therapeutically relevant oncoprotein capable of RNA and DNA binding and mediating protein-protein interactions that drive proliferation, stemness, and resistance to platinum-based therapies. Given our previously published findings, the potential for YB1-driven cisplatin resistance in medulloblastoma (MB), and the limited studies exploring YB1-DNA repair protein interactions, we chose to investigate the role of YB1 in mediating radiation resistance in MB. MB, the most common pediatric malignant brain tumor, is treated with surgical resection, cranio-spinal radiation, and platinum-based chemotherapy, and could potentially benefit from YB1 inhibition. The role of YB1 in the response of MB to ionizing radiation (IR) has not yet been studied but remains relevant for determining potential anti-tumor synergy of YB1 inhibition with standard radiation therapy. We have previously shown that YB1 drives proliferation of cerebellar granular neural precursor cells (CGNPs) and murine Sonic Hedgehog (SHH) group MB cells. While others have demonstrated a link between YB1 and homologous recombination protein binding, functional and therapeutic implications remain unclear, particularly following IR-induced damage. Here we show that depleting YB1 in both SHH and Group 3 MB results not only in reduced proliferation but also synergizes with radiation due to differential response dynamics. YB1 silencing through shRNA followed by IR drives a predominantly NHEJ-dependent repair mechanism, leading to faster γH2AX resolution, premature cell cycle re-entry, checkpoint bypass, reduced proliferation, and increased senescence. These findings show that depleting YB1 in combination with radiation sensitizes SHH and Group 3 MB cells to radiation.

The RNA helicase DDX1 associates with the nuclear RNA exosome and modulates R-loops

The RNA exosome is a ribonuclease complex that mediates both RNA processing and degradation. This complex is evolutionarily conserved, ubiquitously expressed, and required for fundamental cellular functions, including rRNA processing. The RNA exosome plays roles in regulating gene expression and protecting the genome, including modulating the accumulation of RNA-DNA hybrids (R-loops). The function of the RNA exosome is facilitated by cofactors, such as the RNA helicase MTR4, which binds/remodels RNAs. Recently, missense mutations in RNA exosome subunit genes have been linked to neurological diseases. One possibility to explain why missense mutations in genes encoding RNA exosome subunits lead to neurological diseases is that the complex may interact with cell- or tissue-specific cofactors that are impacted by these changes. To begin addressing this question, we performed immunoprecipitation of the RNA exosome subunit, EXOSC3, in a neuronal cell line (N2A) followed by proteomic analyses to identify novel interactors. We identified the putative RNA helicase, DDX1, as an interactor. DDX1 plays roles in double-strand break repair, rRNA processing, and R-loop modulation. To explore the functional connections between EXOSC3 and DDX1, we examined the interaction following double-strand breaks, and analyzed changes in R-loops in N2A cells depleted for EXOSC3 or DDX1 by DNA/RNA immunoprecipitation followed by sequencing (DRIP-Seq). We find that EXOSC3 interaction with DDX1 is decreased in the presence of DNA damage and that loss of EXOSC3 or DDX1 alters R-loops. These results suggest EXOSC3 and DDX1 interact during events of cellular homeostasis and potentially suppress unscrupulous expression of genes promoting neuronal projection.

Deformable CT image registration via a dual feasible neural network

PURPOSE

A quality assurance (QA) CT scans are usually acquired during cancer radiotherapy to assess for any anatomical changes, which may cause an unacceptable dose deviation and therefore warrant a replan. Accurate and rapid deformable image registration (DIR) is needed to support contour propagation from the planning CT (pCT) to the QA CT to facilitate dose volume histogram (DVH) review. Further, the generated deformation maps are used to track the anatomical variations throughout the treatment course and calculate the corresponding accumulated dose from one or more treatment plans.

METHODS

In this study, we aim to develop a deep learning (DL)-based method for automatic deformable registration to align the pCT and the QA CT. Our proposed method, named dual-feasible framework, was implemented by a mutual network that functions as both a forward module and a backward module. The mutual network was trained to predict two deformation vector fields (DVFs) simultaneously, which were then used to register the pCT and QA CT in both directions. A novel dual feasible loss was proposed to train the mutual network. The dual-feasible framework was able to provide additional DVF regularization during network training, which preserves the topology and reduces folding problems. We conducted experiments on 65 head-and-neck cancer patients (228 CTs in total), each with 1 pCT and 2-6 QA CTs. For evaluations, we calculated the mean absolute error (MAE), peak-signal-to-noise ratio (PSNR), structural similarity index (SSIM), target registration error (TRE) between the deformed and target images and the Jacobian determinant of the predicted DVFs.

RESULTS

Within the body contour, the mean MAE, PSNR, SSIM, and TRE are 122.7 HU, 21.8 dB, 0.62 and 4.1 mm before registration and are 40.6 HU, 30.8 dB, 0.94, and 2.0 mm after registration using the proposed method. These results demonstrate the feasibility and efficacy of our proposed method for pCT and QA CT DIR.

CONCLUSION

In summary, we proposed a DL-based method for automatic DIR to match the pCT to the QA CT. Such DIR method would not only benefit current workflow of evaluating DVHs on QA CTs but may also facilitate studies of treatment response assessment and radiomics that depend heavily on the accurate localization of tissues across longitudinal images.

SAMHD1 deacetylation by SIRT1 promotes DNA end resection by facilitating DNA binding at double-strand breaks

Sterile alpha motif and HD domain-containing protein 1 (SAMHD1) has a dNTPase-independent function in promoting DNA end resection to facilitate DNA double-strand break (DSB) repair by homologous recombination (HR); however, it is not known if upstream signaling events govern this activity. Here, we show that SAMHD1 is deacetylated by the SIRT1 sirtuin deacetylase, facilitating its binding with ssDNA at DSBs, to promote DNA end resection and HR. SIRT1 complexes with and deacetylates SAMHD1 at conserved lysine 354 (K354) specifically in response to DSBs. K354 deacetylation by SIRT1 promotes DNA end resection and HR but not SAMHD1 tetramerization or dNTPase activity. Mechanistically, K354 deacetylation by SIRT1 promotes SAMHD1 recruitment to DSBs and binding to ssDNA at DSBs, which in turn facilitates CtIP ssDNA binding, leading to promotion of genome integrity. These findings define a mechanism governing the dNTPase-independent resection function of SAMHD1 by SIRT1 deacetylation in promoting HR and genome stability.

Structural and functional characterization explains loss of dNTPase activity of the cancer-specific R366C/H mutant SAMHD1 proteins

Elevated intracellular levels of dNTPs have been shown to be a biochemical marker of cancer cells. Recently, a series of mutations in the multifunctional dNTP triphosphohydrolase (dNTPase), sterile alpha motif and histidine-aspartate domain-containing protein 1 (SAMHD1), have been reported in various cancers. Here, we investigated the structure and functions of SAMHD1 R366C/H mutants, found in colon cancer and leukemia. Unlike many other cancer-specific mutations, the SAMHD1 R366 mutations do not alter cellular protein levels of the enzyme. However, R366C/H mutant proteins exhibit a loss of dNTPase activity, and their X-ray structures demonstrate the absence of dGTP substrate in their active site, likely because of a loss of interaction with the γ-phosphate of the substrate. The R366C/H mutants failed to reduce intracellular dNTP levels and restrict HIV-1 replication, functions of SAMHD1 that are dependent on the ability of the enzyme to hydrolyze dNTPs. However, these mutants retain dNTPase-independent functions, including mediating dsDNA break repair, interacting with CtIP and cyclin A2, and suppressing innate immune responses. Finally, SAMHD1 degradation in human primary-activated/dividing CD4+ T cells further elevates cellular dNTP levels. This study suggests that the loss of SAMHD1 dNTPase activity induced by R366 mutations can mechanistically contribute to the elevated dNTP levels commonly found in cancer cells.

Abstract PR-002: SIRT2 promotes BRCA1-BARD1 heterodimerization through deacetylation

The breast cancer type I susceptibility protein (BRCA1) and BRCA1-associated RING domain protein I (BARD1) heterodimer promotes genome integrity through pleiotropic functions, including DNA double-strand break (DSB) repair by homologous recombination (HR). BRCA1-BARD1 heterodimerization is required for their mutual stability, HR function, and role in tumor suppression; however, the upstream signaling events governing BRCA1-BARD1 heterodimerization are unclear. Here, we show that SIRT2, a sirtuin deacetylase and breast tumor suppressor, promotes BRCA1-BARD1 heterodimerization through deacetylation. SIRT2 complexes with BRCA1-BARD1 and deacetylates conserved lysines in the BARD1 RING domain, interfacing BRCA1, which promotes BRCA1-BARD1 heterodimerization and consequently BRCA1-BARD1 stability, nuclear retention, and localization to DNA damage sites, as well as efficient HR. Our findings define a mechanism for regulation of BRCA1-BARD1 heterodimerization through SIRT2 deacetylation, elucidating a critical upstream signaling event directing BRCA1-BARD1 heterodimerization, which facilitates HR and tumor suppression, and delineating a role for SIRT2 in directing DSB repair by HR.

Citation Format: Elizabeth V. Minten, Priya Kappor-Vazirani, Chunyang Li, Hui Zhang, Kamakshi Balakrishnan, David S. Yu. SIRT2 promotes BRCA1-BARD1 heterodimerization through deacetylation [abstract]. In: Proceedings of the AACR Virtual Special Conference on Radiation Science and Medicine; 2021 Mar 2-3. Philadelphia (PA): AACR; Clin Cancer Res 2021;27(8_Suppl):Abstract nr PR-002.

SIRT2 promotes BRCA1-BARD1 heterodimerization through deacetylation

The breast cancer type I susceptibility protein (BRCA1) and BRCA1-associated RING domain protein I (BARD1) heterodimer promote genome integrity through pleiotropic functions, including DNA double-strand break (DSB) repair by homologous recombination (HR). BRCA1-BARD1 heterodimerization is required for their mutual stability, HR function, and role in tumor suppression; however, the upstream signaling events governing BRCA1-BARD1 heterodimerization are unclear. Here, we show that SIRT2, a sirtuin deacetylase and breast tumor suppressor, promotes BRCA1-BARD1 heterodimerization through deacetylation. SIRT2 complexes with BRCA1-BARD1 and deacetylates conserved lysines in the BARD1 RING domain, interfacing BRCA1, which promotes BRCA1-BARD1 heterodimerization and consequently BRCA1-BARD1 stability, nuclear retention, and localization to DNA damage sites, thus contributing to efficient HR. Our findings define a mechanism for regulation of BRCA1-BARD1 heterodimerization through SIRT2 deacetylation, elucidating a critical upstream signaling event directing BRCA1-BARD1 heterodimerization, which facilitates HR and tumor suppression, and delineating a role for SIRT2 in directing DSB repair by HR.

Minten et al. show that SIRT2, a sirtuin deacetylase and tumor suppressor protein, promotes BRCA1-BARD1 heterodimerization through deacetylation of BARD1 at conserved lysines within its RING domain. These findings elucidate a critical upstream signaling event directing BRCA1-BARD1 heterodimerization, which facilitates HR and tumor suppression.

Replication stress and FOXM1 drive radiation induced genomic instability and cell transformation

In contrast to the vast majority of research that has focused on the immediate effects of ionizing radiation, this work concentrates on the molecular mechanism driving delayed effects that emerge in the progeny of the exposed cells. We employed functional protein arrays to identify molecular changes induced in a human bronchial epithelial cell line (HBEC3-KT) and osteosarcoma cell line (U2OS) and evaluated their impact on outcomes associated with radiation induced genomic instability (RIGI) at day 5 and 7 post-exposure to a 2Gy X-ray dose, which revealed replication stress in the context of increased FOXM1b expression. Irradiated cells had reduced DNA replication rate detected by the DNA fiber assay and increased DNA resection detected by RPA foci and phosphorylation. Irradiated cells increased utilization of homologous recombination-dependent repair detected by a gene conversion assay and DNA damage at mitosis reflected by RPA positive chromosomal bridges, micronuclei formation and 53BP1 positive bodies in G1, all known outcomes of replication stress. Interference with the function of FOXM1, a transcription factor widely expressed in cancer, employing an aptamer, decreased radiation-induced micronuclei formation and cell transformation while plasmid-driven overexpression of FOXM1b was sufficient to induce replication stress, micronuclei formation and cell transformation.

[Characteristics and diversity of infectious diarrheal caused by various pathogens]

Objective: To understand the characteristics and differences of diarrhea-related symptoms caused by different pathogens, and the clinical features of various pathogens causing diarrhea. Methods: Etiology surveillance program was conducted among 20 provinces of China from 2010 to 2016. The acute diarrhea outpatients were collected from clinics or hospitals. A questionnaire was used to survey demographics and clinical features. VFeces samples were taken for laboratory detection of 22 common diarrhea pathogens, to detect and analyze the clinical symptom pattern characteristics of the patient's. Results: A total of 38 950 outpatients were enrolled from 20 provinces of China. The positive rates of Rotavirus and Norovirus were the highest among the five diarrhea-causing viruses (Rotavirus: 18.29%, Norovirus: 13.06%). In the isolation and culture of 17 diarrhea-causing bacterial, Escherichia coli showed the highest positive rates (6.25%). The clinical features of bacterial diarrhea and viral diarrhea were mainly reflected in the results of fecal traits and routine examination, but pathogenic Vibrio infection was similar to viral diarrhea. Conclusion: Infectious diarrhea presents different characteristics due to various symptoms which can provide a basis for clinical diagnosis.

[Analysis on genetic characteristics of H9N2 avian influenza virus isolated from human infection and external environment in Gansu province]

Objective: To analyze the genomic characteristics of human infection with H9N2 avian influenza virus in Gansu province. Methods: The etiological analysis was conducted for human infection with H9N2 avian influenza virus detected in influenza like illness cases in northwestern China in 2016. Molecular bioinformatics Mega 7.0 software was used to analyze the full genomic sequences of the viral isolate. Results: The gene fragments of HA, NA, MP, NP, NS, PA, PB1 and PB2 of the isolate were highly similar (>90%) to those of H9N2 avian influenza virus strain isolated in external environment in Gansu from 2014 to 2019. The HA gene belonged to BJ/94-like branch, PB2 and MP belonged to G1/97-like branch, and the PB1, PA, NS, and NP genes belonged to F/98-like branch. MP and PB2 were closely related to H7N9, H10N8 and H5N6 viruses. Amino acid sequence alignment showed that the HA cleavage site was arranged in PSRSSR ↓ GLF, H183N and Q226L mutated which included 7 HA glycosylated sites; 62-64 sites of NA absented 3 amino acids (ITE); and M2-31N, NS1-42S, PA-356R, and PA-409N mutated. Conclusions: Apparently, this case of human infection with human infection with H9N2 avian influenza virus was an incidental. However, the isolates of H9N2 influenza virus in external environment of Gansu had a series of mammalian adaptive molecular markers, suggesting that the risk of human infection is higher. It is necessary to strengthen the surveillance by multi departments to deal with influenza pandemic.

EZH2 has a non-catalytic and PRC2-independent role in stabilizing DDB2 to promote nucleotide excision repair

Small cell lung cancer (SCLC) is a highly aggressive malignancy with poor outcomes associated with resistance to cisplatin-based chemotherapy. Enhancer of Zeste Homolog 2 (EZH2) is the catalytic subunit of Polycomb Repressive Complex 2 (PRC2), which silences transcription through trimethylation of histone H3 lysine 27 (H3K27me3) and has emerged as an important therapeutic target with inhibitors targeting its methyltransferase activity under clinical investigation. Here, we show that EZH2 has a non-catalytic and PRC2 independent role in stabilizing DDB2 to promote nucleotide excision repair (NER) and govern cisplatin resistance in SCLC. Using a synthetic lethality screen, we identified important regulators of cisplatin resistance in SCLC cells, including EZH2. EZH2 depletion causes cellular cisplatin and UV hypersensitivity in an epistatic manner with DDB1-DDB2. EZH2 complexes with DDB1-DDB2 and promotes DDB2 stability by impairing its ubiquitination independent of methyltransferase activity or PRC2, thereby facilitating DDB2 localization to cyclobutane pyrimidine dimer (CPD) crosslinks to govern their repair. Furthermore, targeting EZH2 for depletion with DZNep strongly sensitizes SCLC cells and tumors to cisplatin. Our findings reveal a non-catalytic and PRC2-independent function for EZH2 in promoting NER through DDB2 stabilization, suggesting a rationale for targeting EZH2 beyond its catalytic activity for overcoming cisplatin resistance in SCLC.

Improving provider practice patterns in ordering FDG PET/CT for breast cancer patients at a safety-net hospital

e14027

Background: Accurate staging is critical in determining treatment strategies in the management of breast cancer (BC) patients. FDG PET/CT is used to identify the presence of metastatic disease. The criteria for FDG PET/CT utilization is variable, including in any patient with nodal positivity, any patients with systemic symptoms, to those with Stage III disease or higher.. This practice variation has results in different patterns of ordering FDG PET/CT. The preliminary results of a Quality Oncology Practice Initiative (QOPI) audit performed in our Cancer Center in 2017 prompted concern for the over utilization of FDG PET/CT in our BC patients. We performed an initial audit of these practices in 2017 and confirmed these findings. The goal of this study was to re-measure our adherence to NCCN guidelines in 2019 after an educational session complimented by use of a checklist. Methods: A retrospective review was conducted for all BC patients who had FDG PET/CT ordered as initial treatment planning from 1/2017-12/2017. This revealed a 33% rate of failure to meet NCCN guidelines. We then educated our team about the NCCN guidelines for initial PET/CT ordering during our weekly multi-disciplinary conferences, created a test ordering checklist and compared the effect of this education on the use of PET/CT in patients treated at our institution from 1/2019-12/2019. Results: 65 female BC patients had an FDG PET/CT ordered to assist in initial treatment recommendation in 2017. Overall, 66.2% (n = 43) of patients met NCCN indications while 33.8% (n = 22) did not. In comparison to 2017 data, 71 female breast cancer patients had an FDG PET/CT ordered in 2019. Overall, 67 patients (94.4%) met NCCN criteria indications for undergoing FDG PET/CT while only 5 patients (5.6%) did not. Conclusions: Review of FDG PET/CT scans ordered for initial treatment in 2017 revealed that about one third of scans were ordered outside of NCCN guideline recommendations. After an educational session and implementation of a test ordering checklist, we found a marked reduction in the use of FDG PET/CT outside of NCCN guideline recommendations. Although our study is limited by small sample sizes, we identified a practice area that deviated from national recommendations and were able to improve our internal compliance in national guidelines through education and system modification.

[Analysis of the first cluster of cases in a family of COVID-19 in Gansu Province]

The epidemiological history and clinical characteristics of 7 cases of COVID-19 and 1 case of close contact in the first family aggregation epidemic of COVID-19 in Gansu Province were analyzed. The first patient A developed on January 22, 2020, with a history of residence in Wuhan, and confirmed severe cases of NCP on January 24, 2020; patient B, on January 23, 2020, diagnosed on January 31, severe cases; patient C, asymptomatic, diagnosed on January 27; patient D, asymptomatic, diagnosed on January 27; patient E, on January 24, diagnosed on January 28; patient F, asymptomatic, diagnosed on January 31; Patient G was asymptomatic and was diagnosed on January 31. In close contact, H was asymptomatic, PCR test was negative and asymptomatic, and he was discharged early. Among the 7 patients, 1 case died of (B) aggravation, and the other patients' condition was effectively controlled after active treatment. Except for the discharged cases, 5 cases were positive for COVID-19 specific IgM antibody and 1 case was negative. In this clustering outbreak, 4 patients remained asymptomatic, but PCR and IgM antibodies were positive, indicating that asymptomatic patients may be the key point to control the epidemic. Specific IgM antibody screening for patients whose pharyngeal swab nucleic acid test is negative but with ground glass-like lung lesions is very important for early detection and early isolation.

[Epidemiological characteristics of COVID-19 in Gansu province]

Objective: To understand the epidemiological characteristics of COVID-19 cases in different epidemic stages in Gansu province. Methods: Epidemiological investigation was conducted to collect the information of confirmed COVID-19 cases, including demographic, epidemiological and clinical information. Results: As of 25 February 2020, a total of 91 confirmed COVID-19 cases had been reported in Gansu. The epidemic of COVID-19 in Gansu can be divided as three different stages, i.e. imported case stage, imported-case plus indigenous case stage, and indigenous case stage. A total of 63 cases were clustered cases (69.23%), 3 cases were medical staff infected with non-occupational exposure. The initial symptoms included fever (54.95%, 50/91), cough (52.75%, 48/91), or fatigue (28.57%, 26/91), the proportion of each symptom showed a decreasing trend along with the three epidemic stages, but only the differences in proportions of fever (trend χ2=2.20, P<0.05) and fatigue (trend χ2=3.18, P<0.05) among the three epidemic stages were statistically significant. The cases with critical severe symptoms accounted for 42.85% (6/14), 23.73% (14/59) and 16.67% (3/18), respectively, in three epidemic stages, showed a decreasing trend (H=6.45, P<0.05). Also, the incubation period prolonged along with the epidemic stage (F=51.65, P<0.01), but the intervals between disease onset and hospital visit (F=5.32, P<0.01), disease onset and diagnosis (F=5.25, P<0.01) became shorter along with the epidemic stage. Additionally, the basic reproduction number (R0) had decreased from 2.61 in imported case stage to 0.66 in indigenous case stage. Conclusions: The COVID-19 epidemic in Gansu was caused by the imported cases, and about 2/3 cases were clustered ones. No medical worker was observed to be infected by occupational exposure. With the progression of COVID-19 epidemic in Gansu, the change in initial symptom and incubation period suggests, the early screening cannot only depend on body temperature monitoring.

[Analysis of the first cluster of cases in a family of novel coronavirus pneumonia in Gansu Province]

The epidemiological history and clinical characteristics of 7 cases of COVID-19 and 1 case of close contact in the first family aggregation epidemic of COVID-19 in Gansu Province were analyzed. The first patient A developed on January 22, 2020, with a history of residence in Wuhan, and confirmed severe cases of NCP on January 24, 2020; patient B, on January 23, 2020, diagnosed on January 31, severe cases; patient C, asymptomatic, diagnosed on January 27; patient D, asymptomatic, diagnosed on January 27; patient E, on January 24, diagnosed on January 28; patient F, asymptomatic, diagnosed on January 31; Patient G was asymptomatic and was diagnosed on January 31. In close contact, H was asymptomatic, PCR test was negative and asymptomatic, and he was discharged early. Among the 7 patients, 1 case died of (B) aggravation, and the other patients' condition was effectively controlled after active treatment. Except for the discharged cases, 5 cases were positive for COVID-19 specific IgM antibody and 1 case was negative. In this clustering outbreak, 4 patients remained asymptomatic, but PCR and IgM antibodies were positive, indicating that asymptomatic patients may be the key point to control the epidemic. Specific IgM antibody screening for patients whose pharyngeal swab nucleic acid test is negative but with ground glass-like lung lesions is very important for early detection and early isolation.

[Epidemiological and spatial-temporal distribution of several natural focus diseases in Gansu province, 2014-2018]

Objective: To analyze the epidemiological and spatial-temporal distribution of Brucellosis, epidemic encephalitis B and hemorrhagic fever with renal syndrome (HFRS) in Gansu province during 2014-2018 so as to provide evidence for the prevention and control of those diseases. Methods: A database was established in Gansu province from 2014 to 2018, using the geographical information system. A spatial distribution map was drawn, with trend analysis and space-time clustering used to study the 3-dimention of the diseases, by using both ArcGIS 10.5 and SaTScan 9.6 softwares. Results: Results from the trend surface analysis showed that the incidence of Brucellosis decreased gradually from north to south parts while the U type curve could reflect the distribution from the east to the west areas. Incidence of epidemic encephalitis B decreased significantly from south to north areas in the province, with incidence higher in the eastern than in the mid-west region. Difference on the incidence of HFRS was not significantly visible in the eastern and western regions, while the incidence was slightly higher in the southern than the northern parts of the province. Spatial and space-time clustering did exist among the 3 diseases in Gansu from 2014 to 2018. The areas with clusters of Brucellosis appeared in the eastern parts during 2014-2015, including 19 counties. The areas with secondary clusters of Brucellosis were seen in the Hexi district, including 4 counties, during 2017-2018. The areas with high incidence of epidemic encephalitis B were clustered in the middle and southeast areas, including 32 counties, during 2017-2018. Areas with most clusters of HFRS appeared in Min county of Dingxi city in 2018, with the areas of secondary clusters in 8 counties of the eastern areas in 2018. Conclusions: The overall incidence rates of the 3 natural focus diseases were in a upward trend and showing obvious characteristics on spatial clustering. According to the distributive characteristics, effective measures should be developed accordingly.

Acetylation regulates ribonucleotide reductase activity and cancer cell growth

Ribonucleotide reductase (RNR) catalyzes the de novo synthesis of deoxyribonucleoside diphosphates (dNDPs) to provide dNTP precursors for DNA synthesis. Here, we report that acetylation and deacetylation of the RRM2 subunit of RNR acts as a molecular switch that impacts RNR activity, dNTP synthesis, and DNA replication fork progression. Acetylation of RRM2 at K95 abrogates RNR activity by disrupting its homodimer assembly. RRM2 is directly acetylated by KAT7, and deacetylated by Sirt2, respectively. Sirt2, which level peak in S phase, sustains RNR activity at or above a threshold level required for dNTPs synthesis. We also find that radiation or camptothecin-induced DNA damage promotes RRM2 deacetylation by enhancing Sirt2-RRM2 interaction. Acetylation of RRM2 at K95 results in the reduction of the dNTP pool, DNA replication fork stalling, and the suppression of tumor cell growth in vitro and in vivo. This study therefore identifies acetylation as a regulatory mechanism governing RNR activity.

Abstract 3452: hnRNPUL1 regulation by ATR in DNA damage response

The DNA damage response (DDR) is a signaling network that recognizes damages to DNA and orchestrates a variety of DNA repair and cell cycle checkpoint pathways. The DDR is pivotal for cancer prevention. Ataxia Telangiectasia And Rad3-Related Protein (ATR), a protein kinase, functions as an essential transducer of the DDR signaling cascade. ATR primarily responds to single-stranded DNA (ssDNA) generated from double-strand break resection or at stalled replication forks. Depletion of ATR leads to cellular senescence and cancer related phenotypes. The mechanisms regarding how the ATR signal pathway is regulated, however, remain elusive. To discover novel DDR proteins regulated by ATR, we performed proteomic analysis to identify proteins that partner with ATR in response to DNA damage in cells. Our analysis revealed a network of proteins as potential ATR substrates, including Heterogeneous nuclear ribonucleoprotein U-like 1 (hnRPUL1), a protein functions in RNA metabolism. We validated that ATR interacts with hnRNPUL1. In addition, hnRPUL1 is phosphorylated on SQ/TQ sites in response to IR. ATR depletion suppresses the IR induced hnRPUL1 phosphorylation. Our results identify hnRNPUL1 as a novel ATR substrate, critical for the DNA damage response and provide insight into how DDR and RNA metabolism might work synergically in maintaining genomic stability and preventing cancer. Additionally, hnRNPUL1 phosphorylation by ATR may be targeted as an adjunct to improve the efficacy of ionizing radiation for cancer therapy.

Citation Format: Hui Zhang, PamelaSara E. Head, Duc M. Duong, Nicholas T. Seyfried, David S. Yu. hnRNPUL1 regulation by ATR in DNA damage response [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3452.

Abstract 2561: DNA-PKCS deacetylation by SIRT2 promotes DNA double-strand break repair by non-homologous end joining

DNA-dependent protein kinase (DNA-PK) plays a critical role in non-homologous end joining (NHEJ), the predominant pathway that repairs DNA double-strand breaks (DSB) in response to ionizing radiation (IR) to govern genome integrity. How DNA-PK is activated in response to DSBs has remained elusive. Here, we show that the SIRT2 sirtuin deacetylase and tumor suppressor directs the activation of DNA-PK through deacetylation of its catalytic subunit (DNA-PKcs). SIRT2 deacetylase activity governs cellular resistance to DSB-inducing agents and promotes NHEJ. SIRT2 furthermore interacts with and deacetylates DNA-PKcs in response to IR, which facilitates its interaction with Ku and recruitment to DSBs, thereby leading to DNA-PKcs autophosphorylation and DNA-PK signaling to downstream NHEJ substrates. Moreover, SIRT2 inhibitor sensitizes resistant cancer cells and tumors to IR. Our findings define a mechanism for DNA-PK activation by SIRT2-mediated deacetylation, elucidating a critical upstream signaling event initiating the repair of DSBs by NHEJ to promote genome integrity and govern IR resistance, which can be exploited for improvements in cancer therapy.

Citation Format: PamelaSara E. Head, Nagaraju P. Ganji, Shi-Ya Wang, Duc Duong, Hui Zhang, Waaqo Daddacha, Shuyi Li, Nicholas T. Seyfried, David M. Smalley, Ya Wang, Xingming Deng, William S. Dynan, Bassel El-Rayes, Anthony J. Davis, David S. Yu. DNA-PKCS deacetylation by SIRT2 promotes DNA double-strand break repair by non-homologous end joining [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2561.

Survival outcomes by high-risk human papillomavirus status in nonoropharyngeal head and neck squamous cell carcinomas: A propensity-scored analysis of the National Cancer Data Base

BACKGROUND

The prognostic relevance of human papillomavirus (HPV) status in patients with nonoropharyngeal (OPX) squamous cell cancer (SCC) of the head and neck is controversial. In the current study, the authors evaluated the impact of high-risk HPV status on overall survival (OS) in patients with non-OPX SCC using a large database approach.

METHODS

The National Cancer Data Base was queried to identify patients diagnosed from 2004 through 2014 with SCC of the OPX, hypopharynx (HPX), larynx, and oral cavity (OC) with known HPV status. Survival was estimated using Kaplan-Meier methods; distributions were compared using log-rank tests. Propensity score-matching and inverse probability of treatment weighing (IPTW) methods were used; cohorts were matched based on age, sex, Charlson-Deyo score, clinical American Joint Committee on Cancer (AJCC) group stage, treatments received, and anatomic subsite. Propensity analyses were stratified by group stage of disease.

RESULTS

A total of 24,740 patients diagnosed from 2010 through 2013 were analyzed: 1085 patients with HPX, 4804 with laryngeal, 4,018 with OC, and 14,833 with OPX SCC. The percentages of HPV-positive cases by disease site were 17.7% for HPX, 11% for larynx, 10.6% for OC, and 62.9% for OPX. HPV status was found to be prognostic in multiple unadjusted and propensity-adjusted non-OPX populations. HPV positivity was associated with superior OS in patients with HPX SCC with a hazard ratio (HR) of 0.61 (P < .001 by IPTW), in patients with AJCC stage III to IVB laryngeal SCC (HR, 0.79; P = .019 by IPTW), and in patients with AJCC stage III to IVB OC SCC (HR, 0.78; P = .03 by IPTW).

CONCLUSIONS

Positive high-risk HPV status appears to be associated with longer OS in multiple populations of patients with non-OPX head and neck disease (HPX, locally advanced larynx, and OC). If prospectively validated, these findings have implications for risk stratification.

DNA Repair: Translation to the Clinic

It has been well established that an accumulation of mutations in DNA, whether caused by external sources (e.g. ultraviolet light, radioactivity) or internal sources (e.g. metabolic by-products, such as reactive oxygen species), has the potential to cause a cell to undergo carcinogenesis and increase the risk for the development of cancer. Therefore, it is critically important for a cell to have the capacity to properly respond to and repair DNA damage as it occurs. The DNA damage response (DDR) describes a collection of DNA repair pathways that aid in the protection of genomic integrity by detecting myriad types of DNA damage and initiating the correct DNA repair pathway. In many instances, a deficiency in the DDR, whether inherited or spontaneously assumed, can increase the risk of carcinogenesis and ultimately tumorigenesis through the accumulation of mutations that fail to be properly repaired. Interestingly, although disruption of the DDR can lead to the initial genomic instability that can ultimately cause carcinogenesis, the DDR has also proven to be an invaluable target for anticancer drugs and therapies. Making matters more complicated, the DDR is also involved in the resistance to first-line cancer therapy. In this review, we will consider therapies already in use in the clinic and ongoing research into other avenues of treatment that target DNA repair pathways in cancer.

Abstract P1-06-01: Regulation of BRCA1 by SIRT2

We are constantly exposed to a variety of both external and internal DNA damaging agents, such as UV light from the sun and reactive oxygen species created as by-products of aerobic respiration. As a result, our DNA accumulates thousands of instances of damage per cell per day. DNA damage response (DDR) pathways, which include DNA repair and cell-cycle checkpoints, are responsible for the repair of DNA damage and are critical for protecting against mutagenesis and maintaining genome integrity. DNA double-stranded breaks (DSBs) are the most deleterious type of DNA damage and are repaired by one of two pathways: Non-homologous end-joining (NHEJ), an error-prone mechanism of repair active throughout the entire cell cycle, or homologous recombination (HR), considered to be an 'error-free' method for DSB repair that occurs in the S and G2 phases of the cell cycle. Deficiencies in NHEJ or HR can result in genomic instability via genomic incorporation of chromosomal aberrations, which can ultimately lead to an increased risk of cancer. However, in many cases, the mechanisms by which defects in these pathways lead to an increased risk of developing cancer is unknown, making preventative care and treatment of resulting cancers more difficult. Breast Cancer 1 (BRCA1), an established tumor suppressor, is a protein necessary for the proper repair of DNA DSBs through the HR pathway. Defects in BRCA1, whether genetically inherited or spontaneously developed, have been linked to different types of cancer in both men and women, including breast, ovarian, and pancreatic cancer. Yet, the regulation of BRCA1 in HR is not well understood and thus highlights a major a gap in our understanding of how deficiencies in HR contribute to the development of cancer. Our lab has discovered that SIRT2, a class III NAD+ dependent histone deacetylase and putative human tumor suppressor, plays a crucial role in the DDR and repair of DNA DSBs. We have shown that depletion of SIRT2 impairs HR and increases cell sensitivity to ionizing radiation in a deacetylase-dependent manner. A mass spectrometry analysis showed SIRT2 interacts with several proteins involved in DDR, including BRCA1. We validated the interaction between SIRT2 and BRCA1 and found SIRT2 deacetylates BRCA1 both in vitro and in cells. Depletion of SIRT2 and subsequent deacetylation of BRCA1 decreases BRCA1 protein levels in cells, impairing HR. Our results show SIRT2 is a novel regulator of BRCA1 and is critical for the repair of DNA DSBs through HR. These findings provide invaluable insights into how to exploit the interplay between SIRT2 and BRCA1 as a novel therapeutic approach for the prevention and treatment of cancer.

Citation Format: Minten EV, Zhang H, Li C, Head PE, Yu DS. Regulation of BRCA1 by SIRT2 [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-06-01.

Disparities in Postoperative Therapy for Salivary Gland Adenoid Cystic Carcinomas

OBJECTIVES

The patterns of care for salivary gland adenoid cystic carcinomas (ACC) are unknown. We sought to assess predictors of receiving postoperative radiation and/or chemotherapy for patients with nonmetastatic, definitively resected ACC, as well as report unexpected nodal disease.

METHODS

The National Cancer Data Base was queried for definitively resected nonmetastatic ACC from 2004 to 2014. Logistic regression, Kaplan-Meier, and Cox proportional-hazard models were utilized. Propensity-score matched analysis was employed to reduce confounding variables.

RESULTS

A total of 3,136 patients met entry criteria: 2,252 (71.8%) received postoperative radiation, with 223 (7.4%) also receiving concurrent chemotherapy. Median follow-up was 4.87 years. In clinically lymph node negative (cN0) patients, 7.4% had pathologically positive lymph nodes (pN) + after elective neck dissection. Patients who lived closer to their treatment facility and had positive margins were more likely to receive postoperative radiation. Black patients and uninsured patients were less likely to receive radiation. Older age, male sex, advancing stage, and positive surgical margins were associated with worse overall survival (OS). With limited follow-up, receipt of radiation or chemotherapy was not associated with OS.

CONCLUSION

Postoperative radiation was frequently given for resected ACC, with a minority receiving chemotherapy. Black patients and uninsured patients were less likely to receive radiation. Postoperative radiation and/or chemotherapy had no association with OS but were given in greater frequency in more advanced disease, and our series is limited by short follow-up. The disparity findings for this rare disease need to be addressed in future studies.

LEVEL OF EVIDENCE

2c Laryngoscope, 129:377-386, 2019.

[Application of surgical cricothyrotomy in emergency and complicated airway management]

Objective:To explore the feasibility of intercricothyrotomy in emergency airway management. Method:Characteristics of 27 cases underwent surgical cricothyrotomy were analyzed. Result:The main causes of emergency were severe trauma of head and neck, larynx stenosis, interspaces infection of the floor of the mouth and submaxillary space, etc; all the patients were divided into 2 groups : surgical cricothyrotomy as the first choice (group A,16/27) and surgical cricothyrotomy after conventional tracheotomy (group B,11/27); The average time of opening airway for group A was much shorter than group B ［(58.12±24.41)s, (739.09±245.29)s,respectively, P<0.01)］; Bleeding in group A (14 cases) was much less than group B (13 cases) ［(2.36±1.16)ml, (4.65±4.31)ml,respectively, P<0.01］; Except 1 cases died from primary disease, 4 cases with laryngeal stenosis underwent laryngeal dilation with T type expansion tube and 2 cases of bilateral recurrent laryngeal nerve palsy, the average time with tracheal tube of the remaining 20 patients was (12.35±7.29)d, no postoperative complications such as larynx or tracheal stenosis were found. All of them were successfully extubation. Conclusion:Surgical cricothyrotomy procedure is fast and safe with simple and convenient that can be used as the preferred method of rapid airway opening when a critical respiratory tract was difficult to manage.

Abstract A114: SIRT2 directs DNA-PKcs in the DNA damage response

DNA Damage Response (DDR) pathways, including DNA repair and cell-cycle checkpoints, are critical for maintaining genome integrity and preventing disease including cancer. Deficiencies in the DDR result in increased susceptibility to cancer, a leading cause of morbidity and mortality worldwide. However, the mechanisms mediating the activities of the DDR and how their dysregulation leads to genomic instability and a tumor-permissive phenotype are not fully understood. Sirtuin 2 (SIRT2) is a class III NAD+ dependent histone deacetylase implicated in maintaining genomic stability and tumor suppression in that genetic loss of Sirt2 results in both genomic instability and specific murine breast and liver tumors. SIRT2 deficiency in human cells results in hypersensitivity to DNA damage, impaired recovery from replication arrest, and a defect in the G2/M checkpoint in response to ionizing radiation (IR). Preliminary data demonstrate a strong interaction between SIRT2 and DNA-PKcs following IR in human cell lines. DNA-PKcs is a well-established nonhomologous end-joining (NHEJ) mediator kinase that is capable of self-regulation by autophosphorylation at serine 2056 to promote end ligation. SIRT2 knockdown inhibits localization of DNA-PKcs to sites of microirradiation and co-immunoprecipitation with the KU complex in response to IR. Inhibition of localization leads to decreased self-activation of DNA-PKcs at serine 2056 and decreased interaction with KU in SIRT2 knockout lines in response to IR. DNA-PKcs self-phosphorylation and interaction with KU is rescued following damage with wild-type SIRT2 but not with deacetylase dead SIRT2 H187Y, indicating that SIRT2 enzymatic function is necessary for regulation. Overexpression of SIRT2 leads to premature autophosphorylation of DNA-PKcs a serine 2056 without induction of DNA damage. We also demonstrate SIRT2 is capable of deacetylating DNA-PKcs in vitro and in cells. SIRT2 overexpression leads to increased DNA-PKcs self-phosphorylation before and after IR. In addition SIRT2 knockout cell lines exhibit increased sensitivity to IR and CPT. Overall, these data demonstrate that SIRT2 could be a strong potential cancer therapeutic target.

Citation Format: Pamelasara E. Head, Hui Zhang, David S. Yu. SIRT2 directs DNA-PKcs in the DNA damage response [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr A114.

Targeting Mcl-1 enhances DNA replication stress sensitivity to cancer therapy

DNA double-strand breaks (DSBs) are mainly repaired either by homologous recombination (HR) or by nonhomologous end-joining (NHEJ) pathways. Here, we showed that myeloid cell leukemia sequence 1 (Mcl-1) acts as a functional switch in selecting between HR and NHEJ pathways. Mcl-1 was cell cycle-regulated during HR, with its expression peaking in S/G2 phase. While endogenous Mcl-1 depletion reduced HR and enhanced NHEJ, Mcl-1 overexpression resulted in a net increase in HR over NHEJ. Mcl-1 directly interacted with the dimeric Ku protein complex via its Bcl-2 homology 1 and 3 (BH1 and BH3) domains, which are required for Mcl-1 to inhibit Ku-mediated NHEJ. Mcl-1 also promoted DNA resection mediated by the Mre11 complex and HR-dependent DSB repair. Using the Mcl-1 BH1 domain as a docking site, we identified a small molecule, MI-223, that directly bound to BH1 and blocked Mcl-1-stimulated HR DNA repair, leading to sensitization of cancer cells to hydroxyurea- or olaparib-induced DNA replication stress. Combined treatment with MI-223 and hydroxyurea or olaparib exhibited a strong synergy against lung cancer in vivo. This mechanism-driven combination of agents provides a highly attractive therapeutic strategy to improve lung cancer outcomes.

Incidence, prevalence, and mortality of Adamantiades-Behçet's disease in Korea: a nationwide, population-based study (2006-2015)

BACKGROUND

The epidemiology of Adamantiades-Behçet's disease varies among ethnic populations worldwide. Trends in the incidence of Adamantiades-Behçet's disease have not been investigated based on the Korean National Health Insurance database.

OBJECTIVES

This study investigated the incidence and mortality of Adamantiades-Behçet's disease by age using nationwide population data in Korea.

METHODS

A nationwide population-based cohort study was performed using the Korean National Health Insurance Claims Database from 2006 to 2015. The incidence of Adamantiades-Behçet's disease was calculated by age, sex, calendar year and habitat. And comorbid metabolic diseases were also analysed in patients with Adamantiades-Behçet's disease.

RESULTS

The annual incidence of Adamantiades-Behçet's disease per 100 000 person-years was 3.976 (2.587 for males and 5.373 for females) from 2006 to 2015. The incidence of Adamantiades-Behçet's disease peaked among people in their 40s (6.561 per 100 000 person-years). Incidence was significantly higher in subjects with comorbid metabolic conditions, such as diabetes mellitus, hypertension and dyslipidemia. The mortality rate per 1000 person-years increased with age in patients with Adamantiades-Behçet's disease.

CONCLUSIONS

This study showed the incidence, prevalence and mortality of Adamantiades-Behçet's disease. Metabolic conditions increased the risk of Adamantiades-Behçet's disease among Koreans.

[Drug resistance and dissemination of New Delhi metallo-β-lactamase 1 positive bacteria in a patient]

Objective: The aim of this work was to report the surveillance and dissemination of NDM-1 positive bacteria in a patient and ward environment. Methods: In 2010, during the therapy for a 51 years old patient, clinical and environmental samples were collected for carbapenem resistant bacterial culture, according to the clinical microbiological examination. Strains identification and antibiotic susceptibility were tested by VITEK Compact 2 system and E-test. The bla(NDM-1) was detected by PCR and analyzed by sequencing. Plasmids containing bla(NDM-1) were submitted to PFGE-S1 and Southern hybridization. Results: During hospitalization from October 1st to November 4th, nine strains were isolated from blood, sputum, urine, fecal, and ward ground samples. The Klebsiella oxytoca, Raoultella planticola, and Acinetobacter baumannii were isolated from blood sample. The Klebsiella pneumonia and Acinetobacter baumannii were isolated from sputum sample. An Acinetobacter lwoffii was isolated from urine sample. An Escherichia coli was isolated from fecal sample. And the Acinetobacter lwoffii and Acinetobacter spp. were isolated from ward ground. Four strains were NDM-1 positive, which were Raoultella planticola (RpNDM1) isolated from blood, Escherichia coli (EcNDM1) isolated from fecal, Acinetobacter lwoffii (AlDNM1) and Acinetobacter spp. (AsNDM1) isolated from ward ground. Four NDM-1 positive strains were resistant to Piperacillin, Piperacillin tazobactam, Cefepime, Ceftriaxone, Ceftazidime, Imipenem, Meropenem, and Ertapenem. Southern hybridization revealed that bla(NDM-1) were all located on plasmids in the four positive strains. Conclusion:bla(NDM-1) can transfer rapidly among different species, resulting in difficult to control and prevent. While isolating patient who is carrying NDM-1 positive strains, more attention should be paid to the disposal of patient's excreta, especially stool, should be paid more attention.

[Study on the classification of dominant pathogens related to febrile respiratory syndrome, based on the method of Bayes discriminant analysis]

Objective: To understand the dominant pathogens of febrile respiratory syndrome (FRS) patients in Gansu province and to establish the Bayes discriminant function in order to identify the patients infected with the dominant pathogens. Methods: FRS patients were collected in various sentinel hospitals of Gansu province from 2009 to 2015 and the dominant pathogens were determined by describing the composition of pathogenic profile. Significant clinical variables were selected by stepwise discriminant analysis to establish the Bayes discriminant function. Results: In the detection of pathogens for FRS, both influenza virus and rhinovirus showed higher positive rates than those caused by other viruses (13.79%, 8.63%), that accounting for 54.38%, 13.73% of total viral positive patients. Most frequently detected bacteria would include Streptococcus pneumoniae, and haemophilus influenza (44.41%, 18.07%) that accounting for 66.21% and 24.55% among the bacterial positive patients. The original-validated rate of discriminant function, established by 11 clinical variables, was 73.1%, with the cross-validated rate as 70.6%. Conclusion: Influenza virus, Rhinovirus, Streptococcus pneumoniae and Haemophilus influenzae were the dominant pathogens of FRS in Gansu province. Results from the Bayes discriminant analysis showed both higher accuracy in the classification of dominant pathogens, and applicative value for FRS.

Atopic dermatitis is inversely associated with hepatitis B antigen positivity: a population-based cohort study

BACKGROUND

No clear association between hepatitis B virus (HBV) infection and atopic dermatitis (AD) has been established. Some studies have reported that subjects with HBV had an increased risk of atopy; other studies reported an inverse association between HBV seropositivity and allergic diseases.

OBJECTIVE

We evaluated the association between AD and hepatitis B antigen (HBsAg) positivity using Korean National Health and Nutrition Examination Survey data.

METHODS

In total, 14 776 participants aged >19 years were included in the analysis. Multiple logistic regression analyses were used to evaluate the odds ratio of HBsAg positivity in association with AD and asthma.

RESULTS

The prevalence of HBsAg positivity was lower in individuals with AD than in those without AD (mean [SE], 0.7% [0.4] vs. 3.7% [0.2]; P < 0.001). However, HBsAg positivity was not significantly associated with asthma (3.7% [0.2] vs. 2.8% [0.8]; P < 0.001). HBsAg positivity decreased the risk of AD significantly (OR = 0.223; 95% CI = 0.069-0.72).

CONCLUSIONS

This study demonstrates an inverse association between AD and HBsAg positivity using a nationwide, population-based, cross-sectional health examination and survey.

Sirtuin 2 mutations in human cancers impair its function in genome maintenance

mutations in genome maintenance and tumor suppression.

TNFRSF10C copy number variation is associated with metastatic colorectal cancer

BACKGROUND

Genetic markers for distant metastatic disease in patients with colorectal cancer (CRC) are not well defined. Identification of genetic alterations associated with metastatic CRC could help to guide systemic and local treatment strategies. We evaluated the association of tumor necrosis factor receptor superfamily member 10C (TNFRSF10C) copy number variation (CNV) with distant metastatic disease in patients with CRC using The Cancer Genome Atlas (TCGA).

METHODS

Genetic sequencing data and clinical characteristics were obtained from TCGA for all available patients with CRC. There were 515 CRC patient samples with CNV and clinical outcome data, including a subset of 144 rectal adenocarcinoma patient samples. Using the TCGA CRC dataset, CNV of TNFRSF10C was evaluated for association with distant metastatic disease (M1 vs. M0). Multivariate logistic regression analysis with odds ratio (OR) using a 95% confidence interval (CI) was performed adjusting for age, T stage, N stage, adjuvant chemotherapy, gender, microsatellite instability (MSI), location, and surgical margin status.

RESULTS

TNFRSF10C CNV in patients with CRC was associated with distant metastatic disease [OR 4.81 (95% CI, 2.13-10.85) P<0.001] and positive lymph nodes [OR 18.83 (95% CI, 8.42-42.09)]; P<0.001) but not MSI (OR P=0.799). On multivariate analysis, after adjusting for pathologic T stage, N stage, adjuvant chemotherapy, gender, and MSI, TNFRSF10C CNV remained significantly associated with distant metastatic disease (OR P=0.018). Subset analysis revealed that TNFRSF10C CNV was also significantly associated with distant metastatic disease in patients with rectal adenocarcinoma (OR P=0.016).

CONCLUSIONS

TNFRSF10C CNV in patients with CRC is associated with distant metastatic disease. With further validation, such genetic profiles could be used clinically to support optimal systemic treatment strategies versus more aggressive local therapies in patients with CRC, including radiation therapy for rectal adenocarcinoma.

Chromodomain-helicase-DNA binding protein 5, 7 and pronecrotic mixed lineage kinase domain-like protein serve as potential prognostic biomarkers in patients with resected pancreatic adenocarcinomas

Pancreatic cancer is one of the deadliest cancers with a very poor prognosis. Recently, there has been a significant increase in research directed towards identifying potential biomarkers that can be used to diagnose and provide prognostic information for pancreatic cancer. These markers can be used clinically to optimize and personalize therapy for individual patients. In this review, we focused on 3 biomarkers involved in the DNA damage response pathway and the necroptosis pathway: Chromodomain-helicase-DNA binding protein 5, chromodomain-helicase-DNA binding protein 7, and mixed lineage kinase domain-like protein. The aim of this article is to review present literature provided for these biomarkers and current studies in which their effectiveness as prognostic biomarkers are analyzed in order to determine their future use as biomarkers in clinical medicine. Based on the data presented, these biomarkers warrant further investigation, and should be validated in future studies.