An In Vivo Model of Human Macrophages in Metastatic Melanoma.

Despite recent therapeutic progress, advanced melanoma remains lethal for many patients. The composition of the immune tumor microenvironment (TME) has decisive impacts on therapy response and disease outcome, and high-dimensional analyses of patient samples reveal the heterogeneity of the immune TME. Macrophages infiltrate TMEs and generally associate with tumor progression, but the underlying mechanisms are incompletely understood. Because experimental systems are needed to elucidate the functional properties of these cells, we developed a humanized mouse model reconstituted with human immune cells and human melanoma. We used two strains of recipient mice, supporting or not supporting the development of human myeloid cells. We found that human myeloid cells favored metastatic spread of the primary tumor, thereby recapitulating the cancer-supportive role of macrophages. We next analyzed the transcriptome of human immune cells infiltrating tumors versus other tissues. This analysis identified a cluster of myeloid cells present in the TME, but not in other tissues, which do not correspond to canonical M2 cells. The transcriptome of these cells is characterized by high expression of glycolytic enzymes and multiple chemokines and by low expression of gene sets associated with inflammation and adaptive immunity. Compared with humanized mouse results, we found transcriptionally similar myeloid cells in patient-derived samples of melanoma and other cancer types. The humanized mouse model described here thus complements patient sample analyses, enabling further elucidation of fundamental principles in melanoma biology beyond M1/M2 macrophage polarization. The model can also support the development and evaluation of candidate antitumor therapies.

Astrocytic laminin-211 drives disseminated breast tumor cell dormancy in brain.

Although dormancy is thought to play a key role in the metastasis of breast tumor cells to the brain, our knowledge of the molecular mechanisms regulating disseminated tumor cell (DTC) dormancy in this organ is limited. Here using serial intravital imaging of dormant and metastatic triple-negative breast cancer lines, we identify escape from the single-cell or micrometastatic state as the rate-limiting step towards brain metastasis. We show that every DTC occupies a vascular niche, with quiescent DTCs residing on astrocyte endfeet. At these sites, astrocyte-deposited laminin-211 drives DTC quiescence by inducing the dystroglycan receptor to associate with yes-associated protein, thereby sequestering it from the nucleus and preventing its prometastatic functions. These findings identify a brain-specific mechanism of DTC dormancy and highlight the need for a more thorough understanding of tumor dormancy to develop therapeutic approaches that prevent brain metastasis.

Detection of engineered T cells in FFPE tissue by multiplex in situ hybridization and immunohistochemistry.

Identifying engineered T cells in situ is important to understand the location, persistence, and phenotype of these cells in patients after adoptive T cell therapy. While engineered cells are routinely characterized in fresh tissue or blood from patients by flow cytometry, it is difficult to distinguish them from endogenous cells in formalin-fixed, paraffin-embedded (FFPE) tissue biopsies. To overcome this limitation, we have developed a method for characterizing engineered T cells in fixed tissue using in situ hybridization (ISH) to the woodchuck hepatitis post-transcriptional regulatory element (WPRE) common in many lentiviral vectors used to transduce chimeric antigen receptor T (CAR-T) and T cell receptor T (TCR-T) cells, coupled with alternative permeabilization conditions that allows subsequent multiplex immunohistochemical (mIHC) staining within the same image. This new method provides the ability to mark the cells by ISH, and simultaneously stain for cell-associated proteins to immunophenotype CAR/TCR modified T cells within tumors, as well as assess potential roles of these cells in on-target/off-tumor toxicity in other tissue.

Blood pressure control in continuous flow left ventricular assist devices: efficacy and impact on adverse events.

BACKGROUND: Continuous flow (CF) left ventricular assist devices (LVAD) are afterload sensitive and therefore pump performance is affected by hypertension. In addition, poorly controlled hypertension may increase the risk of aortic insufficiency (AI) and stroke. Blood pressure regimens after CF LVAD have not been studied and their impact on rates of AI and stroke are unknown. METHODS: Patients who had CF LVAD at a single center and were supported greater than 30 days were included. Blood pressure was monitored at home by Doppler. Outpatient management of blood pressure was conducted according to a predefined institutional protocol (target mean arterial pressure ≤ 80 mm Hg). RESULTS: A total of 96 patients were included. At the end of follow-up, 25 patients were not on an antihypertensive drug, of these 9 died. Of the 74% receiving antihypertensives, 54% required 1 medication, 34% were on 2, 10% were on 3, and 3% were on 4 or more. Angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers (85% of patients on an antihypertensive) and beta blockers (30%) were the most commonly prescribed medications. There was a significantly higher neurologic event rate in those on no antihypertensives compared with those on antihypertensives (p = 0.009). Only 3% of patients with no or mild AI at baseline progressed to develop moderate or greater AI after a mean of 201 days of follow-up. CONCLUSIONS: Blood pressure control can be achieved in patients with CF LVADs, with the majority of patients requiring only 1 or 2 antihypertensives.