Chemotherapy-induced febrile neutropenia (FN): healthcare resource utilization (HCRU) and costs in commercially insured patients in the US.

PURPOSE: Febrile neutropenia (FN) is a known side effect of chemotherapy, often requiring hospitalization. Economic burden increases with an FN episode and estimates of cost per episode should be updated from real-world data. METHODS: A retrospective claims analysis of FN episodes in patients with non-myeloid malignancies from 2014 to 2021 was performed in IQVIA PharMetrics® Plus database. FN episodes were defined as having same-day claims for neutropenia and fever or infection, plus antibiotic in outpatient settings, following a claim for chemotherapy; index date was defined as the first claim for neutropenia/fever/infection. Patients receiving bone marrow/stem cell transplant and CAR-T therapy were excluded, as were select hematologic malignancies or COVID-19. Healthcare utilization and costs were evaluated and described overall, by episode type (w/wo hospitalization), index year, malignancy type, NCI comorbidity score, and age group. RESULTS: 7,033 FN episodes were identified from 6,825 patients. Most episodes had a hospitalization (91.2%) and 86% of patients had ≥1 risk factor for FN. Overall, FN episodes had a mean (SD) FN-related cost of $25,176 ($39,943). Episodes with hospitalization had higher average FN-related costs versus those without hospitalization ($26,868 vs $7,738), and costs increased with comorbidity score (NCI=0: $23,095; NCI >0-2: $26,084; NCI ≥2: $26,851). CONCLUSIONS: FN continues to be associated with significant economic burden, and varied by cancer type, comorbidity burden, and age. In this analysis, most FN episodes were not preceded by GCSF prophylaxis. The results of this study highlight the opportunity to utilize GCSF in appropriate oncology scenarios.

Analysis of noise levels in the neonatal intensive care unit: the impact of clinical microsystems.

Reorganization of neonatal intensive care by introducing clinical microsystems may help to allocate nursing time more appropriately to the needs of patients. However, there is concern that cohorting infants according to acuity may enhance noise levels. This single-center study investigated the impact of reorganization of neonatal intensive care unit by implementing clinical microsystems in a Level III NICU on environmental noise. This prospective study measured 24-h noise levels over a period of 6 months during pre- and post-implementation of microsystems cohorting infants of similar acuity. Comparative analyses of the mixed acuity (i.e., before) and the cohorting (i.e., after) model were performed by creating daily profiles from continuous noise level measurements and calculating the length of exposure to predefined noise levels. Compared to baseline daytime measurements, noise levels were 3-6 dBA higher during physician handover. Noise levels were 2-3 dBA lower on weekends and 3-4 dBA lower at night, independent of the organizational model. The introduction of clinical microsystems slightly increased average noise levels for high-acuity pods (A and B) but produced a much more substantial decrease for low-acuity pods (E), leading to an overall reduction in unit-wide noise levels.    Conclusion: Our data show that noise levels are more driven by human behavior than by technical devices. Implementation of microsystems may help to reduce noise exposure in the lower acuity pods in a NICU. What is Known: • Excessive noise levels can lead to adverse effects on the health and development of premature infants and other critically ill newborns. • The reorganization of the neonatal intensive care unit following the clinical microsystems principles might improve quality of care but also affect noise exposure of staff and patients. What is New: • The transition from a mixed -acuity to cohorting model is associated with an overall reduction in noise levels, particularly in low-acuity pods requiring less nursing care. • Nevertheless, baseline noise levels in both models exceeded the standard permissible limits.

An Irf6-Esrp1/2 regulatory axis controls midface morphogenesis in vertebrates.

Irf6 and Esrp1 are important for palate development across vertebrates. In zebrafish, we found that irf6 regulates the expression of esrp1 We detailed overlapping Irf6 and Esrp1/2 expression in mouse orofacial epithelium. In zebrafish, irf6 and esrp1/2 share expression in periderm, frontonasal ectoderm and oral epithelium. Genetic disruption of irf6 and esrp1/2 in zebrafish resulted in cleft of the anterior neurocranium. The esrp1/2 mutant also developed cleft of the mouth opening. Lineage tracing of cranial neural crest cells revealed that the cleft resulted not from migration defect, but from impaired chondrogenesis. Analysis of aberrant cells within the cleft revealed expression of sox10, col1a1 and irf6, and these cells were adjacent to krt4+ and krt5+ cells. Breeding of mouse Irf6; Esrp1; Esrp2 compound mutants suggested genetic interaction, as the triple homozygote and the Irf6; Esrp1 double homozygote were not observed. Further, Irf6 heterozygosity reduced Esrp1/2 cleft severity. These studies highlight the complementary analysis of Irf6 and Esrp1/2 in mouse and zebrafish, and identify a unique aberrant cell population in zebrafish expressing sox10, col1a1 and irf6 Future work characterizing this cell population will yield additional insight into cleft pathogenesis.

Why We Swab: A library of stories in stem cell donation.

BACKGROUND: Stories are powerful in their ability to disseminate information in a meaningful way. We hypothesized that a stem cell donation story library optimized for social media could support the education and recruitment of committed unrelated hematopoietic stem cell donors from needed demographic groups. STUDY DESIGN AND METHODS: We developed Why We Swab, a library of stories on stem cell donation (facebook.com/WhyWeSwab; instagram.com/WhyWeSwab; twitter.com/WhyWeSwab), and evaluated its impact across social and traditional media as well as on eligible potential donors' knowledge and attitudes towards donation. RESULTS: As of December 2021, the library included 28 story arcs featuring 45 storytellers from diverse ancestral backgrounds, including 8 donor-recipient stories. Overall, the stories reached >92,000 people across social media. Notably, stories were republished by 18 print/ broadcast media outlets in Canada and by major medical organizations. A series of stories shown to 33 eligible potential donors improved mean total scores on a donation knowledge test (64% to 85%, p < 0.001), reduced mean ambivalence scale scores (3.85 to 2.70, p < 0.001), and improved participants' willingness to register as donors (45% to 73%, p < 0.005). Data are also shown demonstrating that stakeholders valued the library and that its deployment was associated with improved donor recruitment outcomes in Canada. CONCLUSION: Why We Swab is accessible and relevant to a wide audience, including stem cell donor registries and recruitment organizations seeking to improve their recruitment efforts as well as to blood and organ & tissue donation organizations who can adapt the Why We Swab model to their audiences.

Development and evaluation of a community of practice to improve stem cell donor recruitment in Canada.

Background and Objectives Communities of practice (CoPs) represent effective models to achieve quality outcomes in health care. We report the development and evaluation of a CoP to improve stem cell donor recruitment in Canada. Materials and Methods In September 2017, we invited national stakeholders in stem cell donor recruitment to participate in a Facebook group and regular e-meetings. E-meetings involved speakers and roundtable discussion on topics related to donor recruitment. The Facebook group facilitated sharing of resources. We evaluated stakeholder perspective of the CoP and the impact on recruitment outcomes. Results As of December 2020, the CoP included 382 members who published 243 posts to the Facebook group about patient/donor stories (40%), resources (27%), updates/questions (21%) and recruitment outcomes (12%). In January 2020, we surveyed 44 CoP participants; the majority felt that the Facebook group (86%) and e-meetings (59%) supported the community, and that the CoP fostered collaboration (82%), improved their donor recruitment knowledge (75%) and practice (77%) and improved their ability to recruit needed donors (64%). The launch of the CoP correlated with improved donor recruitment outcomes. In 2016-2017, CoP participants recruited 2918 registrants (46% male; 55.9% non-Caucasian) compared to 4531 registrants in 2018-2019 (52.9% male; 62.7% non-Caucasian). Members of the CoP developed innovative resources to support recruitment efforts and led national campaigns securing coverage in major media outlets. Conclusion We describe the first CoP in stem cell donor recruitment to be formally evaluated. The CoP model may be adopted by donor recruitment organisations, registries and blood banks worldwide to improve recruitment outcomes. HIGHLIGHTS: • A community of practice (CoP) in stem cell donor recruitment was valued by participants and supported efforts to improve recruitment outcomes. • The CoP model may be adopted by donor recruitment organizations, donor registries, and blood banks worldwide to improve recruitment outcomes.

Diagnostic accuracy of general dermatologists and supportive oncodermatologists for biopsied cutaneous immune-related adverse events.

PURPOSE: Supportive oncodermatology has been shown to improve several aspects of care for patients with cancer, but research showing improved diagnostic accuracy as a benefit of supportive oncodermatology is largely lacking. We thus aimed to evaluate different dermatologist groups' diagnostic accuracy for heterogenous cutaneous toxicities, using cutaneous immune-related adverse events (cirAEs) from immune checkpoint inhibitors (ICIs) as a test model. METHODS: Billing/requisition codes were used to identify patients who initiated programmed death-1/ligand-1 (PD-1/PD-L1) ICIs between 2010 and 2019 at Dana-Farber Cancer Institute/Brigham and Women's Hospital/Massachusetts General Hospital and underwent a subsequent skin biopsy. For each biopsied cirAE, pre-biopsy clinical diagnoses and post-biopsy clinico-pathologic diagnoses were retrospectively obtained from the medical record. Each biopsy-ordering dermatology provider was categorized as a general dermatologist or supportive oncodermatologist on the basis of providing clinical care within a cancer-center or attending on a hospital/clinic service dedicated to anti-cancer drug-related skin toxicities. RESULTS: Of 4,183 patients who initiated anti-PD-1/PD-L1 therapy between 2010 and 2019, 101 (2.4%) patients collectively had 104 biopsied cirAEs. In more than one-third of all reviewed biopsied cirAEs (n = 39, 37.5%), histopathology results frequently led to revision of the pre-biopsy clinical diagnosis. The rate of initial cirAE misclassification amongst supportive oncodermatologists was significantly lower than that amongst general dermatologists (18/66, 27.3% vs. 21/38, 55.3%; Fischer's-exact-test p = 0.006). CONCLUSION: Experienced supportive oncodermatologists may benefit patient care through increased diagnostic accuracy for skin toxicities from ICIs. Collectively, these results underscore that both skin biopsy from any dermatology provider and oncodermatology referral (where available) are valuable resources that should be integrated into supportive cancer care.

The TFAP2A-IRF6-GRHL3 genetic pathway is conserved in neurulation.

Mutations in IRF6, TFAP2A and GRHL3 cause orofacial clefting syndromes in humans. However, Tfap2a and Grhl3 are also required for neurulation in mice. Here, we found that homeostasis of Irf6 is also required for development of the neural tube and associated structures. Over-expression of Irf6 caused exencephaly, a rostral neural tube defect, through suppression of Tfap2a and Grhl3 expression. Conversely, loss of Irf6 function caused a curly tail and coincided with a reduction of Tfap2a and Grhl3 expression in tail tissues. To test whether Irf6 function in neurulation was conserved, we sequenced samples obtained from human cases of spina bifida and anencephaly. We found two likely disease-causing variants in two samples from patients with spina bifida. Overall, these data suggest that the Tfap2a-Irf6-Grhl3 genetic pathway is shared by two embryologically distinct morphogenetic events that previously were considered independent during mammalian development. In addition, these data suggest new candidates to delineate the genetic architecture of neural tube defects and new therapeutic targets to prevent this common birth defect.

Multimedia resources to support the recruitment of committed hematopoietic stem cell donors: Perspectives of the most-needed donors.

BACKGROUND: Recruitment of committed unrelated hematopoietic stem cell donors from the most-needed demographics remains a challenge for donor recruitment organizations worldwide. Multimedia resources are gaining attention as a modality to support recruitment efforts; however, there is a lack of guidance for the development of such tools. This qualitative study explores the perspectives of eligible stem cell donors on an educational whiteboard video about stem cell donation, generating insights into how whiteboard videos and related multimedia may be optimized for donor recruitment. STUDY DESIGN AND METHODS: Eight semistructured focus groups were conducted with 38 potential donors from the most-needed demographics (young, male, and non-Caucasian) after they had watched a 3.5-minute whiteboard video explaining key concepts in stem cell donation (https://youtu.be/V4fVBtxnWfM). Constructivist grounded theory was used to identify themes and to develop a framework for understanding participants' preferred features of recruitment multimedia. RESULTS: Participants identified a range of features contributing to the effectiveness of recruitment multimedia, adding that the whiteboard video is an effective, integrated, and readily accessible format for supporting donor recruitment. Topics that participants felt are important to address include knowledge gaps regarding donation procedures, concerns about donor safety, and the particular need for specific donor demographics. Suggested avenues for improvement include the addition of donor/recipient/patient personal experiences, attention-grabbing hooks, and a call to action including opportunities for further learning. CONCLUSIONS: Several considerations were generated to inform the development of future multimedia for donor education/recruitment and are relevant to donor recruitment organizations worldwide.

Cutaneous reactions in children treated with MEK inhibitors, BRAF inhibitors, or combination therapy: A multicenter study.

BACKGROUND: Treatment with BRAF inhibitors (BRAFI) and MEK inhibitors (MEKI) causes cutaneous reactions in children, limiting dosing or resulting in treatment cessation. The spectrum and severity of these reactions is not defined. OBJECTIVE: To determine the frequency and spectrum of cutaneous reactions in children receiving BRAFI and MEKI and their effects on continued therapy. METHODS: A multicenter, retrospective study was conducted at 11 clinical sites in the United States and Canada enrolling 99 children treated with BRAFI and/or MEKI for any indication from January 1, 2012, to January 1, 2018. RESULTS: All children in this study had a cutaneous reaction; most had multiple, with a mean per patient of 3.5 reactions on BRAFI, 3.7 on MEKI, and 3.4 on combination BRAFI/MEKI. Three patients discontinued treatment because of a cutaneous reaction. Treatment was altered in 27% of patients on BRAFI, 39.5% on MEKI, and 33% on combination therapy. The cutaneous reactions most likely to alter treatment were dermatitis, panniculitis, and keratosis pilaris-like reactions for BRAFI and dermatitis, acneiform eruptions, and paronychia for MEKI. CONCLUSIONS: Cutaneous reactions are common in children receiving BRAFI and MEKI, and many result in alterations or interruptions in oncologic therapy. Implementing preventative strategies at the start of therapy may minimize cutaneous reactions.

Development and Evaluation of a Whiteboard Video Series to Support the Education and Recruitment of Committed Unrelated Donors for Hematopoietic Stem Cell Transplantation.

Whiteboard videos are a popular video format, allowing viewers to see drawings of concepts alongside explanatory text and speech. We hypothesized that whiteboard videos could support the education and recruitment of unrelated stem cell donors in Canada. A series of 5 sharable whiteboard videos about stem cell donation was produced and posted online in September 2018, including 1 full-length video (https://youtu.be/V4fVBtxnWfM) and 4 shorter videos titled "What Is Stem Cell Transplantation?" "How Does the Matching Process Work?" "How Are Stem Cells Donated?" and "How Can I Register as a Stem Cell Donor?" In the videos, metaphorical interpretations of stem cells as factories and genetic markers as barcode labels are employed to communicate complex concepts. The particular need for young, male, and ethnically diverse donors is reflected in the characters portrayed. Surveys demonstrated the videos (1) were used and valued by stakeholders in donor recruitment and (2) significantly improved objective and self-reported knowledge about stem cell donation and reduced donation-related ambivalence among viewers from the most-needed donor demographics. Use of the whiteboard videos was also associated with improved donor recruitment outcomes in Canada. Our work is relevant to donor registries and recruitment organizations worldwide that seek to improve their recruitment efforts.

Establishment of an in vitro placental barrier model cultured under physiologically relevant oxygen levels.

The human placental barrier facilitates many key functions during pregnancy, most notably the exchange of all substances between the mother and fetus. However, preclinical models of the placental barrier often lacked the multiple cell layers, syncytialization of the trophoblast cells and the low oxygen levels that are present within the body. Therefore, we aimed to design and develop an in vitro model of the placental barrier that would reinstate these factors and enable improved investigations of barrier function. BeWo placental trophoblastic cells and human umbilical vein endothelial cells were co-cultured on contralateral sides of an extracellular matrix-coated transwell insert to establish a multilayered barrier. Epidermal growth factor and forskolin led to significantly increased multi-nucleation of the BeWo cell layer and increased biochemical markers of syncytial fusion, for example syncytin-1 and hCGß. Our in vitro placental barrier possessed size-specific permeability, with 4000-Da molecules experiencing greater transport and a lower apparent permeability coefficient than 70 000-Da molecules. We further demonstrated that the BeWo layer had greater resistance to smaller molecules compared to the endothelial layer. Chronic, physiologically low oxygen exposure (3-8%) increased the expression of hypoxia-inducible factor 1α and syncytin-1, further increased multi-nucleation of the BeWo cell layer and decreased barrier permeability only against smaller molecules (457 Da/4000 Da). In conclusion, we built a novel in vitro co-culture model of the placental barrier that possessed size-specific permeability and could function under physiologically low oxygen levels. Importantly, this will enable future researchers to better study the maternal-fetal transport of nutrients and drugs during pregnancy.

Rapid functional analysis of computationally complex rare human IRF6 gene variants using a novel zebrafish model.

Large-scale sequencing efforts have captured a rapidly growing catalogue of genetic variations. However, the accurate establishment of gene variant pathogenicity remains a central challenge in translating personal genomics information to clinical decisions. Interferon Regulatory Factor 6 (IRF6) gene variants are significant genetic contributors to orofacial clefts. Although approximately three hundred IRF6 gene variants have been documented, their effects on protein functions remain difficult to interpret. Here, we demonstrate the protein functions of human IRF6 missense gene variants could be rapidly assessed in detail by their abilities to rescue the irf6 -/- phenotype in zebrafish through variant mRNA microinjections at the one-cell stage. The results revealed many missense variants previously predicted by traditional statistical and computational tools to be loss-of-function and pathogenic retained partial or full protein function and rescued the zebrafish irf6 -/- periderm rupture phenotype. Through mRNA dosage titration and analysis of the Exome Aggregation Consortium (ExAC) database, IRF6 missense variants were grouped by their abilities to rescue at various dosages into three functional categories: wild type function, reduced function, and complete loss-of-function. This sensitive and specific biological assay was able to address the nuanced functional significances of IRF6 missense gene variants and overcome many limitations faced by current statistical and computational tools in assigning variant protein function and pathogenicity. Furthermore, it unlocked the possibility for characterizing yet undiscovered human IRF6 missense gene variants from orofacial cleft patients, and illustrated a generalizable functional genomics paradigm in personalized medicine.

Sun exposure and protection practices in children after allogeneic hematopoietic stem cell transplantation: A Survey-Based Cross-Sectional Cohort Study.

BACKGROUND/OBJECTIVE: Pediatric hematopoietic stem cell transplantation (HSCT) patients are at an increased risk for skin cancers. Sun exposure is a significant modifiable environmental risk factor. While patient education on sun protection and avoidance behaviors with regular dermatology evaluations are crucial for pediatric HSCT patients, the real-life practice of these sun-protection recommendations in this patient population compared to their peers is unknown. METHODS: A survey-based cross-sectional cohort study was performed in pediatric HSCT patients seen at the Dana-Farber Cancer Institute and Boston Children's Hospital over a 1.5-year period compared with age/sex/Fitzpatrick skin phototype-matched healthy controls. Study participants were surveyed using the validated Glanz survey for pediatric sun protection behavioral research. RESULTS: Eighty-five pediatric HSCT patients and 85 controls completed the study. Pediatric HSCT patients more frequently used sunscreen, hats, umbrellas, and sunglasses and obtained full-body skin exams compared to controls. No difference was observed in sun exposure during hours of peak sun intensity, frequency of purposeful tanning, tanning bed use, and the number of painful sunburns received between pediatric HSCT patients and controls. CONCLUSIONS: Although pediatric HSCT patients practice more sun protection behaviors, they experienced harmful sunburns and intentional tanning behaviors at the same rate as their peers. Patient-directed counseling and strategies to improve patient adherence to optimal sun protection behaviors could have a significant impact on the dermatology quality of life in pediatric HSCT patients.

Characterizing the demographics of chronic pain patients in the state of Maine using the Maine all payer claims database.

BACKGROUND: Chronic pain is currently a significant health problem in the United States. A comprehensive strategy is needed to increase prevention of chronic pain and to improve care for chronic pain patients. However, development of a successful strategy relies, in part, on a better understanding of the demographics and socioeconomics of patients living with chronic pain conditions. The current study was designed to understand the burden of chronic pain in the state of Maine by identifying the prevalence of chronic pain and its relationship with selected demographic and socioeconomic factors in Maine. METHODS: The Maine All Payer Claims Database (MEAPCD) (2006-2011) was used in the secondary data analysis to assess the demographic characteristics (such as age, sex, insurance type, and county of residence) of chronic pain patients in Maine. Chronic pain patients were identified based on the presence of pre-identified chronic pain-associated ICD-9 code(s) and opioid prescription information. Potential associations between the prevalence of chronic pain and a number of socioeconomic factors were determined by comparisons to Maine Census data. RESULTS: More women in the state were identified as having chronic pain across all counties and all age groups (> 10 years old). Surprisingly, the majority of chronic pain patients were identified based on the diagnostic code criteria and not the opioid prescription criteria. A greater utilization of public health insurance was seen within the chronic pain patients. At the county level, although neither education level nor income were associated with the prevalence of chronic pain, these factors significantly correlated with the usage of public health insurance. CONCLUSIONS: Further detailed characterization of the chronic pain patient population in the state of Maine, using multiple data sources, can help design population-targeted strategies to prevent and manage chronic pain.

The Stem Cell Club: a model for unrelated stem cell donor recruitment.

BACKGROUND: Patients with blood, immune, or metabolic diseases may require a stem cell transplant as part of their treatment. However, 70% of patients do not have a suitable human leukocyte antigen match in their family, and need an unrelated donor. Individuals can register as potential donors at stem cell drives, where they provide consent and a tissue sample for human leukocyte antigen typing. The ideal donors are young, male, and from a diversity of ethnic backgrounds. However, in Canada, non-Caucasian males ages 17 to 35 years represent only 8.8% of listed donors. STUDY DESIGN AND METHODS: The Stem Cell Club is a non-profit organization founded in 2011 in Canada that aims to augment recruitment of the most needed donors. The initiative published a recruitment toolkit online (www.stemcellclub.ca). Currently, there are 12 chapters at universities across Canada. RESULTS: To date, the Stem Cell Club has recruited 6585 potential registrants, representing 1.63% of donors on Canada's donor-database. Of the recruited registrants, 58.3% were male; 60.3% of males self-reported as non-Caucasian, and 78.5% were ages 17 to 25 years. From 2015 to 2016, the initiative recruited 13.7% of all ethnically diverse males ages 17 to 35 years listed in Canada's donor database. Data from this initiative demonstrate sustainability and performance on key indicators of stem cell drive quality. CONCLUSION: The Stem Cell Club has developed a capacity to recruit 2600 donors annually, with the majority being males with a high degree of ethnic diversity. The initiative enhances the quality of Canada's unrelated donor-database, improving the chances that patients in need of an unrelated donor will find a match for transplant. The Stem Cell Club is a model relevant to recruitment organizations around the world.

Sparse reconstruction of compressive sensing MRI using cross-domain stochastically fully connected conditional random fields.

BACKGROUND: Magnetic Resonance Imaging (MRI) is a crucial medical imaging technology for the screening and diagnosis of frequently occurring cancers. However, image quality may suffer from long acquisition times for MRIs due to patient motion, which also leads to patient discomfort. Reducing MRI acquisition times can reduce patient discomfort leading to reduced motion artifacts from the acquisition process. Compressive sensing strategies applied to MRI have been demonstrated to be effective in decreasing acquisition times significantly by sparsely sampling the k-space during the acquisition process. However, such a strategy requires advanced reconstruction algorithms to produce high quality and reliable images from compressive sensing MRI. METHODS: This paper proposes a new reconstruction approach based on cross-domain stochastically fully connected conditional random fields (CD-SFCRF) for compressive sensing MRI. The CD-SFCRF introduces constraints in both k-space and spatial domains within a stochastically fully connected graphical model to produce improved MRI reconstruction. RESULTS: Experimental results using T2-weighted (T2w) imaging and diffusion-weighted imaging (DWI) of the prostate show strong performance in preserving fine details and tissue structures in the reconstructed images when compared to other tested methods even at low sampling rates. CONCLUSIONS: The ability to better utilize a limited amount of information to reconstruct T2w and DWI images in a short amount of time while preserving the important details in the images demonstrates the potential of the proposed CD-SFCRF framework as a viable reconstruction algorithm for compressive sensing MRI.

Alterations in STriatal-Enriched protein tyrosine Phosphatase expression, activation, and downstream signaling in early and late stages of the YAC128 Huntington's disease mouse model.

Striatal neurodegeneration and synaptic dysfunction in Huntington's disease are mediated by the mutant huntingtin (mHtt) protein. MHtt disrupts calcium homeostasis and facilitates excitotoxicity, in part by altering NMDA receptor (NMDAR) trafficking and function. Pre-symptomatic (excitotoxin-sensitive) transgenic mice expressing full-length human mHtt with 128 polyglutamine repeats (YAC128 Huntington's disease mice) show increased calpain activity and extrasynaptic NMDAR (Ex-NMDAR) localization and signaling. Furthermore, Ex-NMDAR stimulation facilitates excitotoxicity in wild-type cortical neurons via calpain-mediated cleavage of STriatal-Enriched protein tyrosine Phosphatase 61 (STEP61). The cleavage product, STEP33, cannot dephosphorylate p38 mitogen-activated protein kinase (MAPK), thereby augmenting apoptotic signaling. Here, we show elevated extrasynaptic calpain-mediated cleavage of STEP61 and p38 phosphorylation, as well as STEP61 inactivation and reduced extracellular signal-regulated protein kinase 1/2 phosphorylation (ERK1/2) in the striatum of 6-week-old, excitotoxin-sensitive YAC128 mice. Calpain inhibition reduced basal and NMDA-induced STEP61 cleavage. However, basal p38 phosphorylation was normalized by a peptide disrupting NMDAR-post-synaptic density protein-95 (PSD-95) binding but not by calpain inhibition. In 1-year-old excitotoxin-resistant YAC128 mice, STEP33 levels were not elevated, but STEP61 inactivation and p38 and ERK 1/2 phosphorylation levels were increased. These results show that in YAC128 striatal tissue, enhanced NMDAR-PSD-95 interactions contributes to elevated p38 signaling in early, excitotoxin-sensitive stages, and suggest that STEP61 inactivation enhances MAPK signaling at late, excitotoxin-resistant stages. The YAC128 Huntington's disease mouse model shows early, enhanced susceptibility to NMDA receptor-mediated striatal apoptosis, progressing to late-stage excitotoxicity resistance. This study shows that elevated NMDA receptor-PSD-95 interactions as well as decreased extrasynaptic STriatal-Enriched protein tyrosine Phosphatase 61 (STEP61) activation may contribute to early enhanced apoptotic signaling. In late-stage YAC128 mice, reduced STEP61 levels and activity correlate with elevated MAPK signaling, consistent with excitotoxicity resistance. Solid and dotted arrows indicate conclusions drawn from the current study and other literature, respectively.