Metastatic breast cancers have reduced immune cell recruitment but harbor increased macrophages relative to their matched primary tumors.

The interplay between the immune system and tumor progression is well recognized. However, current human breast cancer immunophenotyping studies are mostly focused on primary tumors with metastatic breast cancer lesions remaining largely understudied. To address this gap, we examined exome-capture RNA sequencing data from 50 primary breast tumors (PBTs) and their patient-matched metastatic tumors (METs) in brain, ovary, bone and gastrointestinal tract. We used gene expression signatures as surrogates for tumor infiltrating lymphocytes (TILs) and compared TIL patterns in PBTs and METs. Enrichment analysis and deconvolution methods both revealed that METs had a significantly lower abundance of total immune cells, including CD8+ T cells, regulatory T cells and dendritic cells. An exception was M2-like macrophages, which were significantly higher in METs across the organ sites examined. Multiplex immunohistochemistry results were consistent with data from the in-silico analysis and showed increased macrophages in METs. We confirmed the finding of a significant reduction in immune cells in brain METs (BRMs) by pathologic assessment of TILs in a set of 49 patient-matched pairs of PBT/BRMs. These findings indicate that METs have an overall lower infiltration of immune cells relative to their matched PBTs, possibly due to immune escape. RNAseq analysis suggests that the relative levels of M2-like macrophages are increased in METs, and their potential role in promoting breast cancer metastasis warrants further study.

Biopsy of enlarging lesions after stereotactic radiosurgery for brain metastases frequently reveals radiation necrosis.

BACKGROUND: Stereotactic radiosurgery (SRS) offers excellent local control for brain metastases (BM) with low rates of toxicity. Radiation necrosis (RN) may occur after treatment and is challenging to distinguish from local recurrence (LR). We evaluated enlarging brain lesions following SRS that were subsequently biopsied to differentiate RN versus LR. METHODS: This study reviewed patients receiving SRS for BM between 2008 and 2012 who underwent a biopsy for suspicion of RN versus LR on MRI. Data collection included demographics, radiation parameters, imaging findings, and post-biopsy pathology. Kaplan-Meier methods determined overall survival. Fisher's exact test assessed for association between lesion biopsy result and variables of interest. RESULTS: Thirty-four patients with 35 biopsied BM were included. Lesions were biopsied a median of 8.8 months after SRS. Most patients had primary lung cancer (11; 31.4%). Eleven (31.4%) biopsies were positive for LR and 24 (68.6%) showed RN only. Median overall survival was longer for patients with RN (31.0 mo) than for patients with LR (14.5 mo; P = 0.135). Time from SRS to biopsy was significantly different between RN and LR groups; 10 lesions (52.5%) biopsied ≤9 months after SRS showed LR, whereas 1 lesion (6.3%) biopsied >9 months after SRS showed LR (P = 0.004). For 16 (65.7%) lesions, management was changed or directed by the biopsy results. CONCLUSIONS: Stereotactic biopsy for accessible enlarging lesions after SRS appears diagnostically valuable in patients with few lesions and changes clinical management. RN should be suspected in patients with an enlarging lesion more than 9 months post-SRS.

Embracing rejection: Immunologic trends in brain metastasis.

Brain metastases represent the most common type of brain tumor. These tumors offer a dismal prognosis and significantly impact quality of life for patients. Their capacity for central nervous system (CNS) invasion is dependent upon induced disruptions to the blood-brain barrier (BBB), alterations to the brain microenvironment, and mechanisms for escaping CNS immunosurveillance. In the emerging era of immunotherapy, understanding how metastases are influenced by the immunologic peculiarities of the CNS will be crucial to forging therapeutic advances. In this review, the immunology of brain metastasis is explored.

Two Rac paralogs regulate polarized growth in the human fungal pathogen Cryptococcus neoformans.

A genome wide analysis of the human fungal pathogen Cryptococcus neoformans var. grubii has revealed a number of duplications of highly conserved genes involved in morphogenesis. Previously, we reported that duplicate Cdc42 paralogs provide C. neoformans with niche-specific responses to environmental stresses: Cdc42 is required for thermotolerance, while Cdc420 supports the formation of titan cells. The related Rho-GTPase Rac1 has been shown in C. neoformans var. neoformans to play a major role in filamentation and to share Cdc42/Cdc420 binding partners. Here we report the characterization of a second Rac paralog in C. neoformans, Rac2, and describe its overlapping function with the previously described CnRac, Rac1. Further, we demonstrate that the Rac paralogs play a primary role in polarized growth via the organization of reactive oxygen species and play only a minor role in the organization of actin. Finally, we provide preliminary evidence that pharmacological inhibitors of Rac activity and actin stability have synergistic activity.