Tumor-localized interleukin-2 and interleukin-12 combine with radiation therapy to safely potentiate regression of advanced malignant melanoma in pet dogs.

PURPOSE: Interleukin-2 and -12 cytokines have potent anti-cancer activity, but suffer a narrow therapeutic window due to off-tumor immune cell activation. Engineering cytokines with the ability to bind and associate with tumor collagen after intratumoral injection potentiated response without toxicity in mice, and was previously safe in pet dogs with sarcoma. Here we sought to test the efficacy of this approach with in dogs with advanced melanoma. EXPERIMENTAL DESIGN: This study examined fifteen client-owned dogs with histologically- or cytologically-confirmed malignant melanoma who received a single 9 Gray fraction of radiation therapy, followed by six cycles of combined collagen-anchored IL-2 and IL-12 therapy Q2W. Cytokine dosing followed a 3+3 dose escalation design, with the initial cytokine dose chosen from prior evaluation in canine sarcomas. No exclusion criteria for tumor stage or metastatic burden, age, weight, or neuter status were applied for this trial. RESULTS: Median survival regardless of tumor stage or dose level was 256 days and 10/13 (76.9%) dogs that completed treatment had CT-measured tumor regression at the treated lesion. In dogs with metastatic disease, 8/13 (61.5%) dogs had partial responses across their combined lesions, evidence of locoregional response. Profiling by Nanostring of treatment-resistant dogs revealed that B2m loss was predictive of poor response to this therapy. CONCLUSIONS: Collectively, these results confirm the ability of locally administered tumor-anchored cytokines to potentiate responses at regional disease sites when combined with radiation. This evidence supports the clinical translation of this approach and highlights the utility of comparative investigation in canine cancers.

Minimizing higher-order aggregation maximizes iron mobilization by small molecules.

The natural product hinokitiol mobilizes iron across lipid bilayers at low concentrations and restores hemoglobinization in iron transporter protein-deficient systems. But hinokitiol fails to similarly mobilize iron at higher concentrations, limiting its uses in chemical biology and medicine. Here we show that at higher concentrations, hinokitiol3:Fe(III) complexes form large, higher-order aggregates, leading to loss of transmembrane iron mobilization. Guided by this understanding and systematic structure-function studies enabled by modular synthesis, we identified FeM-1269, which minimally aggregates and dose-dependently mobilizes iron across lipid bilayers even at very high concentrations. In contrast to hinokitiol, FeM-1269 is also well-tolerated in animals at high doses for extended periods of time. In a mouse model of anemia of inflammation, FeM-1269 increases serum iron, transferrin saturation, hemoglobin and hematocrit. This rationally developed iron-mobilizing small molecule has enhanced potential as a molecular prosthetic for understanding and potentially treating iron transporter deficiencies.

Tumor-localized interleukin-2 and interleukin-12 combine with radiation therapy to safely potentiate regression of advanced malignant melanoma in pet dogs.

The clinical use of interleukin-2 and -12 cytokines against cancer is limited by their narrow therapeutic windows due to on-target, off-tumor activation of immune cells when delivered systemically. Engineering IL-2 and IL-12 to bind to extracellular matrix collagen allows these cytokines to be retained within tumors after intralesional injection, overcoming these clinical safety challenges. While this approach has potentiated responses in syngeneic mouse tumors without toxicity, the complex tumor-immune interactions in human cancers are difficult to recapitulate in mouse models of cancer. This has driven an increased role for comparative oncology clinical trials in companion (pet) dogs with spontaneous cancers that feature analogous tumor and immune biology to human cancers. Here, we report the results from a dose-escalation clinical trial of intratumoral collagen-binding IL-2 and IL-12 cytokines in pet dogs with malignant melanoma, observing encouraging local and regional responses to therapy that may suggest human clinical benefit with this approach.

Canine thyroid carcinomas: A review with emphasis on comparing the compact subtype of follicular thyroid carcinomas and medullary thyroid carcinomas.

Canine thyroid carcinomas are relatively common malignant endocrine neoplasms in dogs derived from either thyroid follicular cells (forming follicular thyroid carcinomas) or medullary cells (parafollicular, C-cells; forming medullary thyroid carcinomas). Older and recent clinical studies often fail to discriminate between compact cellular (solid) follicular thyroid carcinomas and medullary thyroid carcinomas, which may skew conclusions. The compact subtype of follicular thyroid carcinomas appears to be the least differentiated subtype of follicular thyroid carcinomas and needs to be differentiated from medullary thyroid carcinomas. This review includes information on the signalment, presentation, etiopathogenesis, classification, histologic and immunohistochemical diagnosis, clinical management, and biochemical and genetic derangements of canine follicular and medullary carcinomas, and their correlates with human medicine.

Single CAR-T cell treatment controls disseminated ovarian cancer in a syngeneic mouse model.

BACKGROUND: Treatment of some blood cancers with T cells that express a chimeric antigen receptor (CAR) against CD19 have shown remarkable results. In contrast, CAR-T cell efficacy against solid tumors has been difficult to achieve. METHODS: To examine the potential of CAR-T cell treatments against ovarian cancers, we used the mouse ovarian cancer cell line ID8 in an intraperitoneal model that exhibits disseminated solid tumors in female C57BL/6J mice. The CAR contained a single-chain Fv from antibody 237 which recognizes a Tn-glycopeptide-antigen expressed by ID8 due to aberrant O-linked glycosylation in the absence of the transferase-dependent chaperone Cosmc. The efficacy of four Tn-dependent CARs with varying affinity to Tn antigen, and each containing CD28/CD3ζ cytoplasmic domains, were compared in vitro and in vivo in this study. RESULTS: In line with many observations about the impact of aberrant O-linked glycosylation, the ID8Cosmc knock-out (ID8Cosmc-KO) exhibited more rapid tumor progression compared with wild-type ID8. Despite the enhanced tumor growth in vivo, 237 CAR and a mutant with 30-fold higher affinity, but not CARs with lower affinity, controlled advanced ID8Cosmc-KO tumors. Tumor regression could be achieved with a single intravenous dose of the CARs, but intraperitoneal administration was even more effective. The CAR-T cells persisted over a period of months, allowing CAR-treated mice to delay tumor growth in a re-challenge setting. The most effective CARs exhibited the highest affinity for antigen. Antitumor effects observed in vivo were associated with increased numbers of T cells and macrophages, and higher levels of cleaved caspase-3, in the tumor microenvironment. Notably, the least therapeutically effective CAR mediated tonic signaling leading to antigen-independent cytokine expression and it had higher levels of the immunosuppressive cytokine interleukin10. CONCLUSION: The findings support the development of affinity-optimized CAR-T cells as a potential treatment for established ovarian cancer, with the most effective CARs mediating a distinct pattern of inflammatory cytokine release in vitro. Importantly, the most potent Tn-dependent CAR-T cells showed no evidence of toxicity in tumor-bearing mice in a syngeneic, immunocompetent system.

Deep Learning Classification of Breast Cancer Tissue from Terahertz Imaging Through Wavelet Synchro-Squeezed Transformation and Transfer Learning.

Terahertz imaging and spectroscopy is an exciting technology that has the potential to provide insights in medical imaging. Prior research has leveraged statistical inference to classify tissue regions from terahertz images. To date, these approaches have shown that the segmentation problem is challenging for images of fresh tissue and for tumors that have invaded muscular regions. Artificial intelligence, particularly machine learning and deep learning, has been shown to improve performance in some medical imaging challenges. This paper builds on that literature by modifying a set of deep learning approaches to the challenge of classifying tissue regions of images captured by terahertz imaging and spectroscopy of freshly excised murine xenograft tissue. Our approach is to preprocess the images through a wavelet synchronous-squeezed transformation (WSST) to convert time-sequential terahertz data of each THz pixel to a spectrogram. Spectrograms are used as input tensors to a deep convolution neural network for pixel-wise classification. Based on the classification result of each pixel, a cancer tissue segmentation map is achieved. In experimentation, we adopt leave-one-sample-out cross-validation strategy, and evaluate our chosen networks and results using multiple metrics such as accuracy, precision, intersection, and size. The results from this experimentation demonstrate improvement in classification accuracy compared to statistical methods, an improvement to segmentation between muscle and cancerous regions in xenograft tumors, and identify areas to improve the imaging and classification methodology.

Hyperspectral terahertz imaging and optical clearance for cancer classification in breast tumor surgical specimen.

Purpose: We investigate the enhancement in terahertz (THz) images of freshly excised breast tumors upon treatment with an optical clearance agent. The hyperspectral imaging and spectral classifications are used to quantitatively demonstrate the image enhancement. Glycerol solution with 60% concentration is applied to excised breast tumor specimens for various time durations to investigate the effectiveness on image enhancement. Approach: THz reflection spectroscopy is utilized to obtain the absorption coefficient and the index of refraction of untreated and glycerol-treated tissues at each frequency up to 3 THz. Two classifiers, spectral angular mapping (SAM) based on several kernels and Euclidean minimum distance (EMD) are implemented to evaluate the effectiveness of the treatment. The testing raw data is obtained from five breast cancer specimens: two untreated specimens and three specimens treated with glycerol solution for 20, 40, or 60 min. All tumors used in the testing data have healthy tissues adjacent to cancerous ones consistent with the challenge faced in lumpectomy surgeries. Results: The glycerol-treated tissues showed a decrease in the absorption coefficients compared with untreated tissues, especially as the period of treatment increased. Although the sensitivity metric of the classifier presented higher values in the untreated tissues compared with the treated ones, the specificity and accuracy metrics demonstrated higher values for the treated tissues compared with the untreated ones. Conclusions: The biocompatible glycerol solution is a potential optical clearance agent in THz imaging while keeping the histopathology imaging intact. The SAM technique provided a good classification of cancerous tissues despite the small amount of cancer in the training data (only 7%). The SAM exponential kernel and EMD presented classification accuracy of ∼ 80 % to 85% compared with linear and polynomial kernels that provided accuracy ranging from 70% to 80%. Overall, glycerol treatment provides a potential improvement in cancer classification in freshly excised breast tumors.

Engineered ACE2 decoy mitigates lung injury and death induced by SARS-CoV-2 variants.

Vaccine hesitancy and emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants of concern (VOCs) escaping vaccine-induced immune responses highlight the urgency for new COVID-19 therapeutics. Engineered angiotensin-converting enzyme 2 (ACE2) proteins with augmented binding affinities for SARS-CoV-2 spike (S) protein may prove to be especially efficacious against multiple variants. Using molecular dynamics simulations and functional assays, we show that three amino acid substitutions in an engineered soluble ACE2 protein markedly augmented the affinity for the S protein of the SARS-CoV-2 WA-1/2020 isolate and multiple VOCs: B.1.1.7 (Alpha), B.1.351 (Beta), P.1 (Gamma) and B.1.617.2 (Delta). In humanized K18-hACE2 mice infected with the SARS-CoV-2 WA-1/2020 or P.1 variant, prophylactic and therapeutic injections of soluble ACE22.v2.4-IgG1 prevented lung vascular injury and edema formation, essential features of CoV-2-induced SARS, and above all improved survival. These studies demonstrate broad efficacy in vivo of an engineered ACE2 decoy against SARS-CoV-2 variants in mice and point to its therapeutic potential.

Virus viability in spiked swine bone marrow tissue during above-ground burial method and under in vitro conditions.

The emergence of high consequence animal diseases usually requires managing significant mortality. A desirable aspect of any carcass management method is the ability to contain and inactivate the target pathogen. The above-ground burial (AGB) technique was recently developed and proposed as an alternative carcass management method. Here, we investigate the tenacity of swinepox virus (SwPV), as a surrogate model for African swine fever virus (ASFV) in swine carcasses during the AGB process. For this, SwPV was inoculated intrafemorally in 90 adult swine carcasses, which were subsequently disposed under AGB conditions. Bone marrow samples were recovered periodically throughout 12 months and virus viability was assessed by virus isolation (VI), whereas the presence of SwPV DNA was evaluated by quantitative polymerase chain reaction (qPCR). Additionally, an in vitro study assessed the inactivation rate of SwPV, Senecavirus A (SVA), and bovine viral diarrhoea virus (BVDV). Viral suspensions were mixed with bone marrow material and maintained at 21-23°C for 30 days. Virus viability was assessed by VI and viral titration. In the field study, SwPV remained viable only in 11 (55%) bone marrow samples collected on day 7; only viral DNA (and not infectivity) was detected afterwards. SwPV inactivation was estimated to have occurred by day 11. The in vitro testing revealed a variable tenacity of the studied viruses. The viability period was estimated in 28, 80, and 118 days, respectively, for BVDV, SwPV, and SVA. Overall, these findings indicate that the AGB technique was effective in quickly inactivating SwPV. Additionally, the SwPV inactivation rate is comparable to ASFV under field studies and poses a potential model for preliminary ASFV inactivation studies with reduced biosecurity requirements. Moreover, this study contributes to understanding the inactivation kinetics of viruses under specific conditions, which is critical when designing and applying countermeasures in case of biosecurity breaches in sites managing animal mortality.

Mammary tumors in Sprague Dawley rats induced by N-ethyl-N-nitrosourea for evaluating terahertz imaging of breast cancer.

Purpose: The objective of this study is to quantitatively evaluate terahertz (THz) imaging for differentiating cancerous from non-cancerous tissues in mammary tumors developed in response to injection of N-ethyl-N-nitrosourea (ENU) in Sprague Dawley rats. Approach: While previous studies have investigated the biology of mammary tumors of this model, the current work is the first study to employ an imaging modality to visualize these tumors. A pulsed THz imaging system is utilized to experimentally collect the time-domain reflection signals from each pixel of the rat's excised tumor. A statistical segmentation algorithm based on the expectation-maximization (EM) classification method is implemented to quantitatively assess the obtained THz images. The model classification of cancer is reported in terms of the receiver operating characteristic (ROC) curves and the areas under the curves. Results: The obtained low-power microscopic images of 17 ENU-rat tumor sections exhibited the presence of healthy connective tissue adjacent to cancerous tissue. The results also demonstrated that high reflection THz signals were received from cancerous compared with non-cancerous tissues. Decent tumor classification was achieved using the EM method with values ranging from 83% to 96% in fresh tissues and 89% to 96% in formalin-fixed paraffin-embedded tissues. Conclusions: The proposed ENU breast tumor model of Sprague Dawley rats showed a potential to obtain cancerous tissues, such as human breast tumors, adjacent to healthy tissues. The implemented EM classification algorithm quantitatively demonstrated the ability of THz imaging in differentiating cancerous from non-cancerous tissues.

Yttrium-90 Radioembolization to the Prostate Gland: Proof of Concept in a Canine Model and Clinical Translation.

PURPOSE: To investigate the feasibility, safety, and absorbed-dose distribution of prostatic artery radioembolization (RE) in a canine model. MATERIALS AND METHODS: Fourteen male castrated beagles received dihydroandrosterone/estradiol to induce prostatic hyperplasia for the duration of the study. Each dog underwent fluoroscopic prostatic artery catheterization. Yttrium-90 (90Y) microspheres (TheraSphere; Boston Scientific, Marlborough, Massachusetts) were delivered to 1 prostatic hemigland (dose escalation from 60 to 200 Gy), with the contralateral side serving as a control. Assessments for adverse events were performed throughout the follow-up (Common Terminology Criteria for Adverse Events v5.0). Positron emission tomography/magnetic resonance (MR) imaging provided a confirmation after the delivery of absorbed-dose distribution. MR imaging was performed before and 3, 20, and 40 days after RE. Tissue harvest of the prostate, rectum, bladder, urethra, penis, and neurovascular bundles was performed 60 days after RE. RESULTS: All the animals successfully underwent RE. Positron emission tomography/MR imaging demonstrated localization to and good coverage of only the treated hemigland. No adverse events occurred. The MR imaging showed a significant dose-dependent decrease in the treated hemigland size at 40 days (25%-60%, P < .001). No extraprostatic radiographic changes were observed. Necropsy demonstrated no gross rectal, urethral, penile, or bladder changes. Histology revealed RE-induced changes in the treated prostatic tissues of the highest dose group, with gland atrophy and focal necrosis. No extraprostatic RE-related histologic findings were observed. CONCLUSIONS: Prostate 90Y RE is safe and feasible in a canine model and leads to focal dose-dependent changes in the gland without inducing unwanted extraprostatic effects. These results suggest that an investigation of nonoperative prostate cancer is warranted.

Terahertz Imaging and Characterization Protocol for Freshly Excised Breast Cancer Tumors.

This manuscript presents a protocol to handle, characterize, and image freshly excised human breast tumors using pulsed terahertz imaging and spectroscopy techniques. The protocol involves terahertz transmission mode at normal incidence and terahertz reflection mode at an oblique angle of 30°. The collected experimental data represent time domain pulses of the electric field. The terahertz electric field signal transmitted through a fixed point on the excised tissue is processed, through an analytical model, to extract the refractive index and absorption coefficient of the tissue. Utilizing a stepper motor scanner, the terahertz emitted pulse is reflected from each pixel on the tumor providing a planar image of different tissue regions. The image can be presented in time or frequency domain. Furthermore, the extracted data of the refractive index and absorption coefficient at each pixel are utilized to provide a tomographic terahertz image of the tumor. The protocol demonstrates clear differentiation between cancerous and healthy tissues. On the other hand, not adhering to the protocol can result in noisy or inaccurate images due to the presence of air bubbles and fluid remains on the tumor surface. The protocol provides a method for surgical margins assessment of breast tumors.

Breast Cancer Detection with Low-dimension Ordered Orthogonal Projection in Terahertz Imaging.

This paper proposes a new dimension reduction algorithm based on low-dimension ordered orthogonal projection (LOOP), which is used for cancer detection with terahertz (THz) images of freshly excised human breast cancer tissues. A THz image can be represented by a data cube with each pixel containing a high dimension spectrum vector covering several THz frequencies, where each frequency represents a different dimension in the vector. The proposed algorithm projects the high-dimension spectrum vector of each pixel within the THz image into a low-dimension subspace that contains the majority of the unique features embedded in the image. The low-dimension subspace is constructed by sequentially identifying its orthonormal basis vectors, such that each newly chosen basis vector represents the most unique information not contained by existing basis vectors. A multivariate Gaussian mixture model is used to represent the statistical distributions of the low-dimension feature vectors obtained from the proposed dimension reduction algorithm. The model parameters are iteratively learned by using unsupervised learning methods such as Markov chain Monte Carlo or expectation maximization, and the results are used to classify the various regions within a tumor sample. Experiment results demonstrate that the proposed method achieves apparent performance improvement in human breast cancer tissue over existing approaches such as one-dimension Markov chain Monte Carlo. The results confirm that the dimension reduction algorithm presented in this paper is a promising technique for breast cancer detection with THz images, and the classification results present a good correlation with respect to the histopathology results of the analyzed samples.

Terahertz tomographic imaging of freshly excised human breast tissues.

Terahertz imaging and spectroscopy characterization of freshly excised breast cancer tumors are presented in the range 0.15 to 3.5 THz. Cancerous breast tissues were obtained from partial or full removal of malignant tumors while healthy breast tissues were obtained from breast reduction surgeries. The reflection spectroscopy to obtain the refractive index and absorption coefficient is performed on experimental data at each pixel of the tissue, forming tomographic images. The transmission spectroscopy of the refractive index and absorption coefficient are retrieved from experimental data at few tissue points. The average refractive index and absorption coefficients for cancer, fat, and collagen tissue regions are compared between transmission and reflection modes. The reflection mode offers the advantage of retrieving the electrical properties across a significantly greater number of points without the need for sectioning or altering the freshly excised tissue as in the transmission mode. The terahertz spectral power images and the tomographic images demonstrated good qualitative comparison with pathology.

Cancer detection in excised breast tumors using terahertz imaging and spectroscopy.

Terahertz imaging and spectroscopy has demonstrated a potential for differentiating tissue types of excised breast cancer tumors. Pulsed terahertz technology provides a broadband frequency range from 0.1 THz to 4 THz for detecting cancerous tissue. Tumor tissue types of interest include cancer typically manifested as infiltrating ductal or lobular carcinomas, fibro-glandular (healthy connective tissues) and fat. In this work, images of breast tumors excised from human and animal models are reviewed. In addition to alternate fresh tissues, breast cancer tissue phantoms are developed to further evaluate terahertz imaging and the potential use of contrast agents. Terahertz results are successfully validated with pathology images, showing strong differentiation between cancerous and healthy tissues for all freshly excised tissues and types. The advantages, challenges and limitations of THz imaging of breast cancer are discussed.

Pulsed terahertz imaging of breast cancer in freshly excised murine tumors.

This paper investigates terahertz (THz) imaging and classification of freshly excised murine xenograft breast cancer tumors. These tumors are grown via injection of E0771 breast adenocarcinoma cells into the flank of mice maintained on high-fat diet. Within 1 h of excision, the tumor and adjacent tissues are imaged using a pulsed THz system in the reflection mode. The THz images are classified using a statistical Bayesian mixture model with unsupervised and supervised approaches. Correlation with digitized pathology images is conducted using classification images assigned by a modal class decision rule. The corresponding receiver operating characteristic curves are obtained based on the classification results. A total of 13 tumor samples obtained from 9 tumors are investigated. The results show good correlation of THz images with pathology results in all samples of cancer and fat tissues. For tumor samples of cancer, fat, and muscle tissues, THz images show reasonable correlation with pathology where the primary challenge lies in the overlapping dielectric properties of cancer and muscle tissues. The use of a supervised regression approach shows improvement in the classification images although not consistently in all tissue regions. Advancing THz imaging of breast tumors from mice and the development of accurate statistical models will ultimately progress the technique for the assessment of human breast tumor margins.

Assessment of Terahertz Imaging for Excised Breast Cancer Tumors with Image Morphing.

This paper presents an image morphing algorithm for quantitative evaluation methodology of terahertz (THz) images of excised breast cancer tumors. Most current studies on the assessment of THz imaging rely on qualitative evaluation, and there is no established benchmark or procedure to quantify the THz imaging performance. The proposed morphing algorithm provides a tool to quantitatively align the THz image with the histopathology image. Freshly excised xenograft murine breast cancer tumors are imaged using the pulsed THz imaging and spectroscopy system in the reflection mode. Upon fixing the tumor tissue in formalin and embedding in paraffin, an FFPE tissue block is produced. A thin slice of the block is prepared for the pathology image while another THz reflection image is produced directly from the block. We developed an algorithm of mesh morphing using homography mapping of the histopathology image to adjust the alignment, shape, and resolution to match the external contour of the tissue in the THz image. Unlike conventional image morphing algorithms that rely on internal features of the source and target images, only the external contour of the tissue is used to avoid bias. Unsupervised Bayesian learning algorithm is applied to THz images to classify the tissue regions of cancer, fat, and muscles present in xenograft breast tumors. The results demonstrate that the proposed mesh morphing algorithm can provide more effective and accurate evaluation of THz imaging compared with existing algorithms. The results also showed that while THz images of FFPE tissue are highly in agreement with pathology images, challenges remain in assessing THz imaging of fresh tissue.

Pulsed Terahertz Reflection Imaging of tumors in a spontaneous model of breast cancer.

We report the use of reflection-mode terahertz (THz) imaging in a transgenic mouse model of breast cancer. Unlike tumor xenografts that are grown from established cell lines, these tumors were spontaneously generated in the mammary fat pad of mice, and are a better representation of human breast cancer. THz imaging results from 7 tumors that recapitulate the compartmental complexity of breast cancer are presented here. Imaging was first performed on freshly excised tumors within an hour of excision and then repeated after fixation with formalin and paraffin. These THz images were then compared with histopathology to determine reflection-mode signals from specific regions within tumor. Our results demonstrate that the THz signal was consistently higher in cancerous tissue compared with fat, muscle, and fibrous tissue. Almost all tumors presented in this work demonstrated advanced stages where cancer infiltrated other tissues like fat and fibrous stroma. As the first known THz investigation in a transgenic model, these results hold promise for THz imaging at different stages of breast cancer.

Atherosusceptible Shear Stress Activates Endoplasmic Reticulum Stress to Promote Endothelial Inflammation.

Atherosclerosis impacts arteries where disturbed blood flow renders the endothelium susceptible to inflammation. Cytokine activation of endothelial cells (EC) upregulates VCAM-1 receptors that target monocyte recruitment to atherosusceptible regions. Endoplasmic reticulum (ER) stress elicits EC dysregulation in metabolic syndrome. We hypothesized that ER plays a central role in mechanosensing of atherosusceptible shear stress (SS) by signaling enhanced inflammation. Aortic EC were stimulated with low-dose TNFα (0.3 ng/ml) in a microfluidic channel that produced a linear SS gradient over a 20mm field ranging from 0-16 dynes/cm2. High-resolution imaging of immunofluorescence along the monolayer provided a continuous spatial metric of EC orientation, markers of ER stress, VCAM-1 and ICAM-1 expression, and monocyte recruitment. VCAM-1 peaked at 2 dynes/cm2 and decreased to below static TNFα-stimulated levels at atheroprotective-SS of 12 dynes/cm2, whereas ICAM-1 rose to a maximum in parallel with SS. ER expansion and activation of the unfolded protein response also peaked at 2 dynes/cm2, where IRF-1-regulated VCAM-1 expression and monocyte recruitment also rose to a maximum. Silencing of PECAM-1 or key ER stress genes abrogated SS regulation of VCAM-1 transcription and monocyte recruitment. We report a novel role for ER stress in mechanoregulation at arterial regions of atherosusceptible-SS inflamed by low-dose TNFα.