Reversible Chemical Modification of Antibody Effector Function Mitigates Unwanted Systemic Immune Activation.

Antibody effector functions including antibody-dependent cellular cytotoxicity (ADCC) and phagocytosis (ADCP) are mediated through the interaction of the antibody Fc region with Fcγ receptors present on immune cells. Several approaches have been used to modulate antibody Fc-Fcγ interactions with the goal of driving an effective antitumor immune response, including Fc point mutations and glycan modifications. However, robust antibody-Fcγ engagement and immune cell binding of Fc-enhanced antibodies in the periphery can lead to the unwanted induction of systemic cytokine release and other dose-limiting infusion-related reactions. Creating a balance between effective engagement of Fcγ receptors that can induce antitumor activity without incurring systemic immune activation is an ongoing challenge in the field of antibody and immuno-oncology therapeutics. Herein, we describe a method for the reversible chemical modulation of antibody-Fcγ interactions using simple poly(ethylene glycol) (PEG) linkers conjugated to antibody interchain disulfides with maleimide attachments. This method enables dosing of a therapeutic with muted Fcγ engagement that is restored in vivo in a time-dependent manner. The technology was applied to an effector function enhanced agonist CD40 antibody, SEA-CD40, and experiments demonstrate significant reductions in Fc-induced immune activation in vitro and in mice and nonhuman primates despite showing retained efficacy and improved pharmacokinetics compared to the parent antibody. We foresee that this simple, modular system can be rapidly applied to antibodies that suffer from systemic immune activation due to peripheral FcγR binding immediately upon infusion.

The vedotin antibody-drug conjugate payload drives platform-based nonclinical safety and pharmacokinetic profiles.

Nonclinical safety and pharmacokinetic data for MMAE and 14 vedotin ADCs were evaluated to determine patterns of toxicity, consistency of pharmacokinetic results, and species differences between rats and monkeys. Most nonclinical toxicities were antigen-independent, common across ADCs, and included hematologic, lymphoid, and reproductive toxicity related to MMAE pharmacology. Hematologic toxicity was the dose-limiting or predominant toxicity for the majority of vedotin ADCs in both species. Tissue expression of the targeted antigen of an ADC rarely correlated with dose-limiting toxicity (DLT); only two ADCs had antigen-dependent skin DLTs. For two additional ADCs, antigen-dependent delivery of MMAE in the bone marrow may have exacerbated the antigen-independent hematologic DLT. The highest tolerated doses and pharmacokinetics were similar within a given species, with rats tolerating higher doses than monkeys. Studies longer than one month in duration detected the same or fewer toxicities than one-month studies and had no additional findings that affected the human risk assessment. These data support opportunities to streamline ADC toxicity assessments without compromising human starting dose selection or target organ identification.

Efficacy and Durability of Intravenous Ertapenem Therapy for Recalcitrant Hidradenitis Suppurativa.

Importance: Hidradenitis suppurativa (HS) is a debilitating follicular skin disorder in which bacterial colonization is typical. Oral antibiotic efficacy can be unreliable; however, selective intravenous antibiotics, specifically ertapenem, may provide favorable clinical outcomes. Objective: To explore optimal course duration, efficacy, and patient satisfaction associated with intravenous ertapenem for HS. Design, Setting, and Participants: This retrospective review of the medical records of 98 patients with HS between 2018 and 2022 measured and evaluated patient outcomes before and after treatment with intravenous ertapenem. Participants were followed up in a telephone survey assessing patient perspectives and satisfaction. All of those included in this study received medical care from the Albert Einstein College of Medicine's Montefiore HS Center. Exposures: Patients were treated with 1 g of ertapenem that was self-administered at home through a peripheral intravenous central catheter using an elastomeric pump for 12 to 16 weeks. Antiandrogens and immunomodulatory biologic therapies initiated prior to ertapenem were maintained throughout the treatment course. Main Outcomes and Measures: The primary outcomes, encompassing clinical severity (evaluated through the HS Physician Global Assessment score [a 6-point scale ranging from clear to very severe] and a numerical rating scale for pain [an 11-point scale in which a score of 0 indicates no pain and a score of 10 indicates the worst possible pain]) and markers of inflammation (such as leukocytes, erythrocyte sedimentation rate, C-reactive protein, and interleukin-6), were measured at baseline, the midcourse of intravenous ertapenem treatment, at the end of the course, and posttherapy. Bacterial abundance was also examined at these 4 points, and patient satisfaction was assessed during follow-up. Results: A total of 98 patients (mean [SD] age, 35.8 [13.0] years; 61 [62.2%] female) with HS were treated with intravenous ertapenem. The self-reported racial distribution included 3 individuals identifying as Asian (3.1%), 59 as Black/African American (60.2%), 13 as White (13.3%), and 23 as either other or unknown (23.5%). Additionally, 24 participants (24.5%) reported Spanish/Hispanic/Latino ethnicity. The mean (SD) treatment duration spanned 13.1 (4.0) weeks, with posttherapy follow-up occurring after 7.8 (3.6) weeks. From baseline to posttherapy follow-up, significant reductions were found in the mean (SD) HS Physician Global Assessment scores (3.9 [1.0] vs 2.7 [1.2]; P < .001) and the numerical rating scale for pain (4.2 [3.3] vs 1.8 [2.7]; P < .001), C-reactive protein (5.4 [11.4] vs 2.4 [2.0] mg/dL; P < .001), interleukin-6 (25.2 [21.1] vs 13.7 [13.9]; P < .001), and leukocytes (11.34 [3.9] vs 10.0 [3.4]; P < .001). At follow-up, 76 patients (78.0%) participated in the telephone survey, where 63 (80.3%) reported medium to high satisfaction; further, 69 (90.8%) would recommend ertapenem to other patients. Conclusions and Relevance: In this retrospective review of medical records and telephone survey, treating HS with intravenous ertapenem, administered for a mean of 13 weeks, was associated with improvement in clinical and inflammatory markers, as well as heightened patient satisfaction. Nonetheless, this approach should be monitored for the emergence of antimicrobial resistance given a longer than standard treatment course.

A propensity score matched analysis of liver transplantation outcomes in the setting of preservation solution shortage.

The recent shortage of the University of Wisconsin (UW) solution prompted increased utilization of histidine-tryptophan-ketoglutarate (HTK) solution for liver graft preservation. This contemporary study analyzed deceased donor liver transplant outcomes following preservation with HTK vs UW. Patients receiving deceased donor liver transplantations between January 1, 2019, and June 30, 2022, were retrospectively identified utilizing the Organ Procurement and Transplant Network database, stratified by preservation with HTK vs UW, and a propensity score matching analysis was performed. Outcomes assessed included rates of primary nonfunction, graft survival, and patient survival. There were 4447 patients in each cohort. Primary nonfunction occurred in 60 (1.35%) patients in the HTK group vs 25 (0.54%) in the UW group (P < .001). HTK was associated with lower 90-day graft survival (94.39% vs 96.09%; P < .001) and 90-day patient survival (95.97% vs 97.38%; P = .001). Unmatched donation after cardiac death-specific analysis of HTK vs UW demonstrated respective rates of primary nonfunction of 1.63% vs 0.82% (P = .20), 90-day graft survival of 92.50% vs 95.29% (P = .069), and 90-day patient survival of 93.90% vs 96.35% (P = .077). These results suggest that HTK may not be an equivalent preservation solution for deceased donor liver transplantation.

Comprehensive Interactome Mapping of the DNA Repair Scaffold SLX4 Using Proximity Labeling and Affinity Purification.

The DNA repair scaffold SLX4 has pivotal roles in cellular processes that maintain genome stability, most notably homologous recombination. Germline mutations in SLX4 are associated with Fanconi anemia, a disease characterized by chromosome instability and cancer susceptibility. The role of mammalian SLX4 in homologous recombination depends critically on binding and activating structure-selective endonucleases, namely SLX1, MUS81-EME1, and XPF-ERCC1. Increasing evidence indicates that cells rely on distinct SLX4-dependent complexes to remove DNA lesions in specific regions of the genome. Despite our understanding of SLX4 as a scaffold for DNA repair proteins, a detailed repertoire of SLX4 interactors has never been reported. Here, we provide a comprehensive map of the human SLX4 interactome using proximity-dependent biotin identification (BioID) and affinity purification coupled to mass spectrometry (AP-MS). We identified 221 unique high-confidence interactors, of which the vast majority represent novel SLX4-binding proteins. Network analysis of these hits revealed pathways with known involvement of SLX4, such as DNA repair, and several emerging pathways of interest, including RNA metabolism and chromatin remodeling. In summary, the comprehensive SLX4 interactome we report here provides a deeper understanding of how SLX4 functions in DNA repair while revealing new cellular processes that may involve SLX4.

Split Brachioradialis Tendon Causing Wartenberg Syndrome in a Professional Baseball Pitcher.

Wartenberg syndrome can occur when external factors compress the superficial radial nerve. It can also be due to anatomic variations, such as a split brachioradialis tendon entrapping the nerve. This case report describes a unique example of a professional baseball player diagnosed with Wartenberg syndrome who was later found to have a split brachioradialis tendon during surgical management. It is an important addition to the field of hand surgery since, to our knowledge, we have not identified such a rare case concerning a professional athlete previously described in the literature.

Adalimumab efficacy is inversely correlated with body mass index (BMI) in hidradenitis suppurativa.

BACKGROUND: Adalimumab is the only FDA-approved biologic for hidradenitis suppurativa (HS). In the setting of increasing obesity rates worldwide, the relationship between adalimumab efficacy for HS and BMI is essential to understand. We assessed this relationship through markers of disease severity and inflammation. METHODS: Institutional review board-approved retrospective chart review of Montefiore/Einstein HS Center (HSC) patients (n = 57) treated with adalimumab. The relationship between BMI and adalimumab efficacy was assessed through disease severity (HS-Physician Global Assessment [HS-PGA] 0 and Numerical Rating Scale Pain [NRS-Pain]) and inflammatory markers (erythrocyte sedimentation rate [ESR], C-reactive protein [CRP], and interleukin-6 [IL-6]). A BMI ≥ 30 is defined as obese; BMI < 30 is defined as non-obese. RESULTS: The mean age was 35.8 ± 13.0 years. After adalimumab therapy, those with BMI < 30 experienced significant reductions in HS-PGA (-1.5 ± 0.9; P < 0.0001) and NRS-Pain (-1.6 ± 2.1; P < 0.0001), as well as mean decreases in inflammatory markers ESR, CRP, and IL-6 (-17.90 ± 23.6, -0.71 ± 1.4, -5.88 ± 7.9, respectively; P > 0.05). Obese patients (BMI ≥ 30) experienced mean increases in HS-PGA (+0.22 ± 0.8; P > 0.05) and NRS-Pain scores (+1.41 ± 3.5; P > 0.05) as well as mean increases in ESR, CRP, and IL-6 (+2.62 ± 28.3, +0.44 ± 3.0, +2.35 ± 6.9, respectively; P > 0.05). Comparing the cohorts, differences in changes in HS-PGA, NRS-Pain, ESR, and IL-6 after therapy are significantly different (P < 0.05). CONCLUSIONS: We identified significantly lower efficacy of adalimumab in HS patients with BMI ≥ 30 compared to those with BMI < 30. Those with BMI ≥ 30 demonstrated signs of both clinical and physiological deterioration while on adalimumab. Future studies are needed to examine adalimumab dosing for HS patients with high BMI, as well as a critical reconsideration of weight-based therapies.

Development of a yeast whole-cell biocatalyst for MHET conversion into terephthalic acid and ethylene glycol.

BACKGROUND: Over the 70 years since the introduction of plastic into everyday items, plastic waste has become an increasing problem. With over 360 million tonnes of plastics produced every year, solutions for plastic recycling and plastic waste reduction are sorely needed. Recently, multiple enzymes capable of degrading PET (polyethylene terephthalate) plastic have been identified and engineered. In particular, the enzymes PETase and MHETase from Ideonella sakaiensis depolymerize PET into the two building blocks used for its synthesis, ethylene glycol (EG) and terephthalic acid (TPA). Importantly, EG and TPA can be re-used for PET synthesis allowing complete and sustainable PET recycling. RESULTS: In this study we used Saccharomyces cerevisiae, a species utilized widely in bioindustrial fermentation processes, as a platform to develop a whole-cell catalyst expressing the MHETase enzyme, which converts monohydroxyethyl terephthalate (MHET) into TPA and EG. We assessed six expression architectures and identified those resulting in efficient MHETase expression on the yeast cell surface. We show that the MHETase whole-cell catalyst has activity comparable to recombinant MHETase purified from Escherichia coli. Finally, we demonstrate that surface displayed MHETase is active across a range of pHs, temperatures, and for at least 12 days at room temperature. CONCLUSIONS: We demonstrate the feasibility of using S. cerevisiae as a platform for the expression and surface display of PET degrading enzymes and predict that the whole-cell catalyst will be a viable alternative to protein purification-based approaches for plastic degradation.

HPV vaccination uptake among foreign-born Blacks in the US: insights from the National Health Interview Survey 2013-2017.

INTRODUCTION: Human papillomavirus (HPV) vaccination uptake is lower among foreign-born than US-born individuals, but HPV-related (e.g., cervical) cancer risks are disproportionately higher among immigrant populations. Although timely vaccination can help reduce these risks, less is known about differences in the low HPV vaccination uptake among foreign-born groups, especially Black immigrants. The purpose of this study was to examine the differences in HPV vaccination initiation among US- and foreign-born Black men and women. METHOD: Data from the 2013-2017 National Health Interview Survey on Black adults, aged 18-37 years, were analyzed in 2019. HPV vaccination initiation prevalence among US- and foreign-born blacks by region of birth were examined. Multivariate binary logistic regression analysis was used to examine the relationship between foreign-birth status and HPV vaccination initiation separately among men and women, after adjusting for sociodemographic and health-related factors. RESULTS: There were significant differences (p < 0.001) in HPV vaccination initiation among Blacks from the US (22.5%), Africa (14.2%), and Americas/Caribbean Islands (11.4%). Adjusted odds of HPV vaccination initiation were lower among foreign- than US-born Blacks (AOR 0.71, CI 0.52, 0.98) but insignificant after controlling for health-related factors. Being ≤ 17 years versus 18-26 years at age of vaccine eligibility (AOR 3.44, CI 2.90, 4.07) was associated with HPV vaccination, and this relationship remained significant among men and women. Being single was associated with vaccination initiation among men, and some college experience, fair/poor health, obstetric/gynecological visit, and pap test were associated with HPV vaccination. Conclusion Cancer prevention strategies to promote HPV vaccination should consider making age-appropriate, gender-specific, and culturally relevant programs among foreign-born blacks in the US. Health insurance is also a key factor that might help with the lower rates of vaccinated black immigrants.

The Society for Vascular Surgery Objective Performance Goals for Critical Limb Ischemia are attainable in select patients with ischemic wounds managed with wound care alone.

BACKGROUND: To set therapeutic benchmarks, in 2009 the Society for Vascular Surgery defined objective performance goals (OPG) for treatment of patients with chronic limb threatening ischemia (CLTI) with either open surgical bypass or endovascular intervention. The goal of these OPGs are to set standards of care from a revascularization standpoint and to provide performance benchmarks for 1 year patency rates for new endovascular therapies. While OPGs are useful in this regard, a critical decision point in the treatment of patients with CLTI is determining when revascularization is necessary. There is little guidance in the comprehensive treatment of this patient population, especially in the nonoperative cohort. Guidelines are needed for the CLTI patient population as a whole and not just those revascularized, and our aim was to assess whether CLTI OPGs could be attained with nonoperative management alone. METHODS: Our cohort included patients with an incident diagnosis of CLTI (by hemodynamic and symptomatic criteria) at our institution from 2013-2017. The primary outcome measured was mortality. Secondary outcomes were limb loss and failure of amputation-free survival. Descriptive statistics were used to define the 2 groups - patients undergoing primary revascularization and patients undergoing primary wound management. The risk difference in outcomes between the 2 groups was estimated using collaborative-targeted maximum likelihood estimation. RESULTS: Our cohort included 349 incident CLTI patients; 60% male, 51% white, mean age 63 +/- 13 years, 20% Rutherford 4, and 80% Rutherford 5. Most patients (277, 79%) underwent primary revascularization, and 72 (21%) were treated with wound care alone. Demographics and presenting characteristics were similar between groups. Although the revascularized patients were more likely to have femoropopliteal disease (72% vs. 36%), both groups had a high rate of infrapopliteal disease (62% vs. 57%). Not surprisingly, the patients in the revascularization group were less likely to have congestive heart failure (34% vs. 42%), complicated diabetes (52% vs. 79%), obesity (19% vs. 33%), and end stage renal disease (14% vs. 28%). In the wound care group, 2-year outcomes were 65% survival, 51% amputation free survival, 19% major limb amputation, and 17% major adverse cardiac event. The wound care cohort had a 13% greater risk of death at 2 years; however, the risk of limb loss at 2 years was 12% less in the wound care cohort. CONCLUSIONS: A comprehensive set treatment goals and expected amputation free survival outcomes can guide revascularization, but also assure that appropriate outcomes are achieved for patients treated without revascularization. The 2-year outcomes achieved in this cohort provide an estimate of outcomes for nonrevascularized CLTI patients. Although multi-center or prospective studies are needed, we demonstrate that equal, even improved, limb salvage rates are possible.

An open-source platform to quantify subnuclear foci and protein colocalization in response to replication stress.

Nuclear reorganization, including the localization of proteins into discrete subnuclear foci, is a hallmark of the cellular response to DNA damage and replication stress. These foci are thought to represent transient environments or repair factories, in which the lesion is sequestered with molecules and co-factors that catalyze repair. For example, nuclear foci contain signaling proteins that recruit transducer proteins. One important class of transducers is the structure-selective endonucleases, such as SLX1-SLX4, MUS81-EME1, and XPF-ERCC1, which remove branched DNA structures that form during repair. The relocalization of structure-selective endonucleases into subnuclear foci provides a visual read-out for the presence of direct DNA damage, replication barriers, or DNA entanglements and can be monitored using fluorescence microscopy. By simultaneously probing for two or more fluorescent signals, fluorescence microscopy can also provide insights into the proximal association of proteins within a local environment. Here, we report an open-source and semi-automated method to detect and quantify subnuclear foci, as well as foci colocalization and the accompanying pixel-based colocalization metrics. We use this pipeline to show that pre-mitotic nuclei contain a basal threshold of foci marked by SLX1-SLX4, MUS81, or XPF. Some of these foci colocalize with FANCD2 and have a high degree of correlation and co-occurrence. We also show that pre-mitotic cells experiencing replication stress contain elevated levels of foci containing SLX1-SLX4 or XPF, but not MUS81. These results point towards a role for SLX1-SLX4 and XPF-ERCC1 in the early cellular response to replication stress. Nevertheless, most of the foci that form in response to replication stress contain either FANCD2 or one of the three endonucleases. Altogether, our work highlights the compositional heterogeneity of subnuclear foci that form in response to replication stress. We also describe a user-friendly pipeline that can be used to characterize these dynamic structures.

Rosacea associated with dupilumab therapy.

Background: Dupilumab is used for treatment of atopic dermatitis through blockade of IL-4 and IL-13 signaling of the Th2 pathway. Recent case reports have described alopecia, psoriasis, persistent facial dermatitis, and recall dermatitis at patch test sites after the initiation of dupilumab therapy.Case report: We describe the case of a 67-year-old female with atopic dermatitis who developed recurrent episodic flares of rosacea temporally associated with dupilumab injections that resolved after dupilumab discontinuation.Conclusion: The cause of rosacea-like reaction associated with dupilumab treatment is unknown. Th2 pathway inhibition by dupilumab may promote Demodex proliferation and increased IL-17-mediated inflammation implicated in the pathophysiology of rosacea.Abbreviations: atopic dermatitis: AD; interleukin: IL; persistent facial dermatitis: PFD; T-helper cell type 1: Th1; T-helper cell type 2: Th2; T-helper cell type 17: Th17; tumor necrosis factor-∝: TNF-∝.

A Review of Noninvasive Techniques for Skin Cancer Detection in Dermatology.

As a result of increasing melanoma incidence and challenges with clinical and histopathologic evaluation of pigmented lesions, noninvasive techniques to assist in the assessment of skin lesions are highly sought after. This review discusses the methods, benefits, and limitations of adhesive patch biopsy, electrical impedance spectroscopy (EIS), multispectral imaging, high-frequency ultrasonography (HFUS), optical coherence tomography (OCT), and reflectance confocal microscopy (RCM) in the detection of skin cancer. Adhesive patch biopsy provides improved sensitivity and specificity for the detection of melanoma without a trade-off of higher sensitivity for lower specificity seen in other diagnostic tools to aid in skin cancer detection, including EIS and multispectral imaging. EIS and multispectral imaging provide objective information based on computer-assisted diagnosis to assist in the decision to biopsy and/or excise an atypical melanocytic lesion. HFUS may be useful for the determination of skin tumor depth and identification of surgical borders, although further studies are necessary to determine its accuracy in the detection of skin cancer. OCT and RCM provide enhanced resolution of skin tissue and have been applied for improved accuracy in skin cancer diagnosis, as well as monitoring the response of nonsurgical treatments of skin cancers and the determination of tumor margins and recurrences. These novel approaches to skin cancer assessment offer opportunities to dermatologists, but are dependent on the individual dermatologist's comfort, knowledge, and desire to invest in training and implementation of noninvasive techniques. These noninvasive modalities may have a role in the complementary assessment of skin cancers, although histopathologic diagnosis remains the gold standard for the evaluation of skin cancer.

AXL Is a Putative Tumor Suppressor and Dormancy Regulator in Prostate Cancer.

Prostate cancer bone metastasis remains lethal and incurable, and often arises years after elimination of the primary tumor. It is unclear what underlies the decades-long clinical latency before recurrence, but evidence points to the existence of dormant residual tumor cells that disseminated before the primary tumor was eliminated. To design therapies to prevent progression of disseminated tumor cells (DTC) into lethal metastases, it is crucial to understand the mechanism(s) underlying this dormancy. The current study functionally validated our previous observation that implicated the GAS6/AXL axis in mediating DTC dormancy in the bone marrow. AXL-null and AXL-overexpressing prostate cancer cell lines were generated to determine if AXL was necessary and/or sufficient for dormancy. Characterization of these cells in vitro and using in vivo mouse models of DTC growth demonstrated that AXL was indeed sufficient to induce dormancy, but was unable to maintain it long-term and was not absolutely required for a dormancy period. Clinically, AXL expression correlated with longer survival in prostate cancer patients, and AXL was not expressed by cancer cells in primary or metastatic tissue. These data point to a tumor-suppressive role for AXL in prostate cancer, and future work is required to determine if AXL is expressed on human bone marrow DTCs. IMPLICATIONS: The ability of AXL to initiate but not maintain dormancy, coupled with its dispensability, suggests that targeting AXL alone will not prevent lethal metastatic outgrowth, and likely a cooperative network of factors exists to mediate long-term cellular dormancy.

Prostate-specific markers to identify rare prostate cancer cells in liquid biopsies.

Despite improvements in early detection and advances in treatment, patients with prostate cancer continue to die from their disease. Minimal residual disease after primary definitive treatment can lead to relapse and distant metastases, and increasing evidence suggests that circulating tumour cells (CTCs) and bone marrow-derived disseminated tumour cells (BM-DTCs) can offer clinically relevant biological insights into prostate cancer dissemination and metastasis. Using epithelial markers to accurately detect CTCs and BM-DTCs is associated with difficulties, and prostate-specific markers are needed for the detection of these cells using rare cell assays. Putative prostate-specific markers have been identified, and an optimized strategy for staining rare cancer cells from liquid biopsies using these markers is required. The ideal prostate-specific marker will be expressed on every CTC or BM-DTC throughout disease progression (giving high sensitivity) and will not be expressed on non-prostate-cancer cells in the sample (giving high specificity). Some markers might not be specific enough to the prostate to be used as individual markers of prostate cancer cells, whereas others could be truly prostate-specific and would make ideal markers for use in rare cell assays. The goal of future studies is to use sensitive and specific prostate markers to consistently and reliably identify rare cancer cells.

Optimization of prostate cancer cell detection using multiplex tyramide signal amplification.

Approximately 29 000 men die of prostate cancer (PCa) each year in the United States, and 90% to 100% of them are due to incurable bone metastasis. It is difficult to determine (1) when PCa disseminates in the natural history of the disease; (2) where cancer cell disseminates before becoming overt metastatic lesions; and (3) which tumors are aggressive and which are indolent. Tumor tissue and liquid (blood and bone marrow) biopsies provide important information to answer these questions, but significant limitations exist for immunostaining strategies that assess protein expression in these tissues. Classic immunohistochemistry (IHC) assays can typically assess expression of one or two proteins per tissue section. We have developed a novel immunofluorescence staining protocol to detect a panel of seven proteins on PCa tissue from primary tumor biopsies and metastatic lesion autopsy tissue, as well as cancer cells from liquid biopsies. We used a tyramide-based system to amplify the true signal and optimized the protocol to reduce background signal, thereby boosting the signal-to-noise ratio. Any protein-specific antibody in this protocol can be exchanged for a different validated antibody. This protocol therefore, represents a highly informative and flexible assay that can be used to provide important information about cancer tissue for the purpose of improving detection, diagnosis, and treatment.

Optimization of Immunofluorescent Detection of Bone Marrow Disseminated Tumor Cells.

BACKGROUND: Cancer metastasis is the primary cause of cancer-related deaths and remains incurable. Current clinical methods for predicting metastatic recurrence are not sensitive enough to detect individual cancer cells in the body; therefore, current efforts are directed toward liquid biopsy-based assays to capture circulating and disseminated tumor cells (CTCs and DTCs) in the blood and bone marrow, respectively. The most promising strategy is fluorescence-based immunostaining using cancer cell-specific markers. However, despite recent efforts to develop robust processing and staining platforms, results from these platforms have been discordant among groups, particularly for DTC detection. While the choice of cancer cell-specific markers is a large factor in this discordance, we have found that marker-independent factors causing false signal are just as critical to consider. Bone marrow is particularly challenging to analyze by immunostaining because endogenous immune cell properties and bone marrow matrix components typically generate false staining. For immunostaining of whole tumor tissue containing ample cancer cells, this background staining can be overcome. Application of fluorescent-based staining for rare cells, however, is easily jeopardized by immune cells and autofluorescence that lead to false signal. RESULTS: We have specifically found two types of background staining in bone marrow samples: autofluorescence of the tissue and non-specific binding of secondary antibodies. We systematically optimized a basic immunofluorescence protocol to eliminate this background using cancer cells spiked into human bone marrow. This enhanced the specificity of automated scanning detection software. Our optimized protocol also outperformed a commercial rare cell detection protocol in detecting candidate DTCs from metastatic patient bone marrow. CONCLUSIONS: Robust optimization to increase the signal-to-noise ratio of immunofluorescent staining of bone marrow is required in order to achieve the necessary sensitivity and specificity for rare cell detection. Background immunofluorescent staining in bone marrow causes uncertainty and inconsistency among investigators, which can be overcome by systematically addressing each contributing source. Our optimized assay eliminates sources of background signal, and is adaptable to automated staining platforms for high throughput analysis.