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

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

Immune niches in brain metastases contain TCF1+ stem-like T cells, are associated with disease control and are modulated by preoperative SRS.

The CD8+ T-cell response is prognostic for survival outcomes in several tumor types. However, whether this extends to tumors in the brain, an organ with barriers to T cell entry, remains unclear. Here, we analyzed immune infiltration in 67 brain metastasis (BrM) and found high frequencies of PD1+ TCF1+ stem-like CD8+ T-cells and TCF1- effector-like cells. Importantly, the stem-like cells aggregate with antigen presenting cells in immune niches, and niches were prognostic for local disease control. Standard of care for BrM is resection followed by stereotactic radiosurgery (SRS), so to determine SRS's impact on the BrM immune response, we examined 76 BrM treated with pre-operative SRS (pSRS). pSRS acutely reduced CD8+ T cells at 3 days. However, CD8+ T cells rebounded by day 6, driven by increased frequency of effector-like cells. This suggests that the immune response in BrM can be regenerated rapidly, likely by the local TCF1+ stem-like population.

Renal protection by atorvastatin in a murine model of sickle cell nephropathy.

Recent studies have demonstrated pleiotropic effects of statins in various mouse models of kidney disease. In this study, Townes humanized sickle cell mice were treated for 8 weeks with atorvastatin at a dose of 10 mg/kg/day starting at 10 weeks of age. Treatment with atorvastatin significantly reduced albuminuria, and improved both urine concentrating ability and glomerular filtration rate. Atorvastatin also decreased markers of kidney injury and endothelial activation, and ameliorated oxidant stress in renal tissues and peripheral macrophages. Atorvastatin downregulated the expression of mRNA levels of the NADPH oxidases, Cybb (also termed Nox2) and Nox4, which are major sources of oxidant stress in the kidney. These findings highlight the pleiotropic effects of atorvastatin and suggest that it may provide beneficial effects in sickle cell nephropathy.

Lectins identify glycan biomarkers on glioblastoma-derived cancer stem cells.

Glioblastoma (GBM) is a highly aggressive primary brain tumor with a poor prognosis. Despite aggressive therapy with surgery, radiotherapy, and chemotherapy, nearly all patients succumb to disease within 2 years. Several studies have supported the presence of stem-like cells in brain tumor cultures that are CD133-positive, are capable of self-renewal, and give rise to all cell types found within the tumor, potentially perpetuating growth. CD133 is a widely accepted marker for glioma-derived cancer stem cells; however, its reliability has been questioned, creating a need for other identifiers of this biologically important subpopulation. We used a panel of 20 lectins to identify differences in glycan expression found in the glycocalyx of undifferentiated glioma-derived stem cells and differentiated cells that arise from them. Fluorescently labeled lectins that specifically recognize α-N-acetylgalactosamine (GalNAc) and α-N-acetylglucosamine (GlcNAc) differentially bound to the cell surface based on the state of cellular differentiation. GalNAc and GlcNAc were highly expressed on the surface of undifferentiated cells and showed markedly reduced expression over a 12-day duration of differentiation. Additionally, the GalNAc-recognizing lectin Dolichos biflorus agglutinin was capable of specifically selecting and sorting glioma-derived stem cell populations from an unsorted tumor stock and this subpopulation had proliferative properties similar to CD133(+) cells in vitro and also had tumor-forming capability in vivo. Our preliminary results on a single cerebellar GBM suggest that GalNAc and GlcNAc are novel biomarkers for identifying glioma-derived stem cells and can be used to isolate cancer stem cells from unsorted cell populations, thereby creating new cell lines for research or clinical testing.

Cotreatment with BCL-2 antagonist sensitizes cutaneous T-cell lymphoma to lethal action of HDAC7-Nur77-based mechanism.

Pan-histone deacetylase inhibitors, for example, vorinostat and panobinostat (LBH589; Novartis Pharmaceuticals, East Hanover, NJ), have shown clinical efficacy against advanced cutaneous T-cell lymphoma (CTCL). However, the molecular basis of this activity remains unclear. HDAC7, a class IIA histone deacetylase (HDAC), is overexpressed in thymocytes, where it represses expression of the proapoptotic nuclear orphan receptor Nur77. Here, we demonstrate that treatment with panobinostat rapidly inhibits the in vitro and intracellular activity, as well as the mRNA and protein levels of HDAC7, and induces expression and translocation of Nur77 to the mitochondria. There, Nur77 converts death resistance protein Bcl-2 into a killer protein, promoting cell death of cultured and patient-derived human CTCL cells. Treatment with panobinostat improved survival of athymic nude mice implanted with human CTCL cells. Ectopic expression of Nur77 induced apoptosis and sensitized HH cells to panobinostat, whereas combined knockdown of Nur77 and its family member Nor1 was necessary to inhibit panobinostat-induced apoptosis of CTCL cells. Cotreatment with the Bcl-2/Bcl-x(L) antagonist ABT-737 decreased resistance and synergistically induced apoptosis of human CTCL cells. These findings mechanistically implicate HDAC7 and Nur77 in sensitizing human CTCL cells to panobinostat as well as suggest that cotreatment with an anti-Bcl-2 agent would augment the anti-CTCL activity of panobinostat.