Leptomeningeal metastasis in breast cancer - a systematic review

Background

There is limited data on the impact of specific patient characteristics, tumor subtypes or treatment interventions on survival in breast cancer LM.

Methods

A systematic review was conducted to assess the impact of hormone receptor and HER-2 status on survival in breast cancer LM. A search for clinical studies published between 1/1/2007 and 7/1/2012 and all randomized-controlled trials was performed. Survival data from all studies are reported by study design (prospective trials, retrospective cohort studies, case studies).

Results

A total of 36 studies with 851 LM breast cancer subjects were identified. The majority (87%) were treated with intrathecal chemotherapy. Pooled median overall survival ranged from 14.9-18.1 weeks depending on study type. Breast cancer LM survival (15 weeks) was longer than other solid tumor LM 8.3 weeks and lung cancer LM 8.7 weeks, but shorter than LM lymphoma (15.4 versus 24.2 weeks). The impact of hormone receptor and HER-2 status on survival could not be determined.

Conclusions

A median overall survival of 15 weeks in prospective studies of breast cancer LM provides a historical comparison for future LM breast cancer trials. Other outcomes including the impact of molecular status on survival could not be determined based on available studies.

Restriction spectrum imaging: An evolving imaging biomarker in prostate MRI

Restriction spectrum imaging (RSI) is a novel diffusion-weighted MRI technique that uses the mathematically distinct behavior of water diffusion in separable microscopic tissue compartments to highlight key aspects of the tissue microarchitecture with high conspicuity. RSI can be acquired in less than 5 min on modern scanners using a surface coil. Multiple field gradients and high b-values in combination with postprocessing techniques allow the simultaneous resolution of length-scale and geometric information, as well as compartmental and nuclear volume fraction filtering. RSI also uses a distortion correction technique and can thus be fused to high resolution T2-weighted images for detailed localization, which improves delineation of disease extension into critical anatomic structures. In this review, we discuss the acquisition, postprocessing, and interpretation of RSI for prostate MRI. We also summarize existing data demonstrating the applicability of RSI for prostate cancer detection, in vivo characterization, localization, and targeting.

LEVEL OF EVIDENCE

5 J. Magn. Reson. Imaging 2017;45:323-336.

Molecular mechanisms of OLIG2 transcription factor in brain cancer

Oligodendrocyte lineage transcription factor 2 (OLIG2) plays a pivotal role in glioma development. Here we conducted a comprehensive study of the critical gene regulatory networks involving OLIG2. These include the networks responsible for OLIG2 expression, its translocation to nucleus, cell cycle, epigenetic regulation, and Rho-pathway interactions. We described positive feedback loops including OLIG2: loops of epigenetic regulation and loops involving receptor tyrosine kinases. These loops may be responsible for the prolonged oncogenic activity of OLIG2. The proposed schemes for epigenetic regulation of the gene networks involving OLIG2 are confirmed by patient survival (Kaplan-Meier) curves based on the cancer genome atlas (TCGA) datasets. Finally, we elucidate the Coherent-Gene Modules (CGMs) networks-framework of OLIG2 involvement in cancer. We showed that genes interacting with OLIG2 formed eight CGMs having a set of intermodular connections. We showed also that among the genes involved in these modules the most connected hub is EGFR, then, on lower level, HSP90 and CALM1, followed by three lower levels including epigenetic genes KDM1A and NCOR1. The genes on the six upper levels of the hierarchy are involved in interconnections of all eight CGMs and organize functionally defined gene-signaling subnetworks having specific functions. For example, CGM1 is involved in epigenetic control. CGM2 is significantly related to cell proliferation and differentiation. CGM3 includes a number of interconnected helix-loop-helix transcription factors (bHLH) including OLIG2. Many of these TFs are partially controlled by OLIG2. The CGM4 is involved in PDGF-related: angiogenesis, tumor cell proliferation and differentiation. These analyses provide testable hypotheses and approaches to inhibit OLIG2 pathway and relevant feed-forward and feedback loops to be interrogated. This broad approach can be applied to other TFs.

Brainstem Glioma in Adults

Brainstem gliomas are not nearly as common in adults as they are in children. They are likely the final common consequence not of a single disease process but of several. They can be difficult to diagnose, and are challenging to treat. Clinical studies of this diagnosis are few and generally small. Because of these factors, our understanding of the biology of adult brainstem glioma is incomplete. However, the knowledge base is growing and progress is being made. In this article, we review the current state of knowledge for brainstem glioma in adults and identify key areas for which additional information is required.

Demonstration of Non-Gaussian Restricted Diffusion in Tumor Cells Using Diffusion Time-Dependent Diffusion-Weighted Magnetic Resonance Imaging Contrast

The diffusion-weighted magnetic resonance imaging (DWI) technique enables quantification of water mobility for probing microstructural properties of biological tissue and has become an effective tool for collecting information about the underlying pathology of cancerous tissue. Measurements using multiple b-values have indicated biexponential signal attenuation, ascribed to “fast” (high ADC) and “slow” (low ADC) diffusion components. In this empirical study, we investigate the properties of the diffusion time (Δ)-dependent components of the diffusion-weighted (DW) signal in a constant b-value experiment. A xenograft gliobastoma mouse was imaged using Δ = 11 ms, 20 ms, 40 ms, 60 ms, and b = 500–4000 s/mm² in intervals of 500 s/mm². Data were corrected for EPI distortions, and the Δ-dependence on the DW-signal was measured within three regions of interest [intermediate- and high-density tumor regions and normal-appearing brain (NAB) tissue regions]. In this study, we verify the assumption that the slow decaying component of the DW-signal is non-Gaussian and dependent on Δ, consistent with restricted diffusion of the intracellular space. As the DW-signal is a function of Δ and is specific to restricted diffusion, manipulating Δ at constant b-value (cb) provides a complementary and direct approach for separating the restricted from the hindered diffusion component. We found that Δ-dependence is specific to the tumor tissue signal. Based on an extended biexponential model, we verified the interpretation of the diffusion time-dependent contrast and successfully estimated the intracellular restricted ADC, signal volume fraction, and cell size within each ROI.

A Phase II randomized study of galunisertib monotherapy or galunisertib plus lomustine compared with lomustine monotherapy in patients with recurrent glioblastoma

BACKGROUND

The combination of galunisertib, a transforming growth factor (TGF)-β receptor (R)1 kinase inhibitor, and lomustine was found to have antitumor activity in murine models of glioblastoma.

METHODS

Galunisertib (300 mg/day) was given orally 14 days on/14 days off (intermittent dosing). Lomustine was given as approved. Patients were randomized in a 2:1:1 ratio to galunisertib + lomustine, galunisertib monotherapy, or placebo + lomustine. The primary objective was overall survival (OS); secondary objectives were safety, pharmacokinetics (PKs), and antitumor activity.

RESULTS

One hundred fifty-eight patients were randomized: galunisertib + lomustine (N = 79), galunisertib (N = 39), and placebo + lomustine (N = 40). Baseline characteristics were: male (64.6%), white (75.3%), median age 58 years, ECOG performance status (PS) 1 (63.3%), and primary glioblastoma (93.7%). The PKs of galunisertib were not altered with lomustine, and galunisertib had a median half-life of ∼8 hours. Median OS in months (95% credible interval [CrI]) for galunisertib + lomustine was 6.7 (range: 5.3-8.5), 8.0 (range: 5.7-11.7) for galunisertib alone, and 7.5 (range: 5.6-10.3) for placebo + lomustine. There was no difference in OS for patients treated with galunisertib + lomustine compared with placebo + lomustine [P (HR < 1) = 26%]. Median progression-free survival of ∼2 months was observed in all 3 arms. Among 8 patients with IDH1 mutation, 7 patients were treated with galunisertib (monotherapy or with lomustine); OS ranged from 4 to 17 months. Patients treated with galunisertib alone had fewer drug-related grade 3/4 adverse events (n = 34) compared with lomustine-treated patients (10% vs 26%). Baseline PS, post-discontinuation of bevacizumab, tumor size, and baseline levels of MDC/CCL22 were correlated with OS.

CONCLUSIONS

Galunisertib + lomustine failed to demonstrate improved OS relative to placebo + lomustine. Efficacy outcomes were similar in all 3 arms.

CLINICAL TRIAL REGISTRATION

NCT01582269, ClinicalTrials.gov.

Abstract 3030: CT179: A novel small molecule Olig2 inhibitor for the treatment of glioblastoma

Glioblastoma (GBM) is an orphan disease with a high unmet medical need. Despite optimal treatment, the median survival is only 12 to 15 months in GBM patients of which only 4% achieve 5-year survival. OLIG2 is a transcription factor that is almost exclusively expressed in the CNS that has been linked to the tumorigenesis of GBM cells and their resistance to radiotherapy. Importantly OLIG2 is a key transcription factor that maintains the stemness of the glial stem cells, drives proliferation and invasion and recurrent tumor growth. Inhibitors of this pathway are therefore of interest as potential treatments for this unmet need.

CT-179 is a small molecule inhibitor that was initially designed to prevent homodimerization of Olig2. CT-179 is highly cytotoxic to OLIG2 expressing GBM cells with a high therapeutic index for non-OLIG2 expressing cell types. This inhibitor demonstrates functional inhibition of the OLIG2 pathway through specific reduction in nuclear Olig2 protein levels in treated cells. A cell pathway analysis indicates that CT-179 impacts GBM proliferation through cell cycle arrest and induction of apoptosis. Secondarily an immunosuppression mechanism-of-action may also be relevant. CT-179 penetrates the CNS to attain high brain concentrations at levels far in excess of its cytotoxicity to GBM cells. Efficacy studies reveal dose dependent reductions of tumor growth which is enhanced with radiotherapy. CT-179 demonstrates impressive extension of survival in orthotopic human PDX GBM. Safety studies indicate that there is a large therapeutic window. The compound has a long half-life, low metabolism and has excellent formulation properties and PK supporting once per day oral dosing. CT-179 show promise as both a cytotoxic agent and as potential radiosensitizer for use in the treatment of GBM.

Citation Format: Gordon Alton, Graham Beaton, Susan Knowles, Greg Stein, Rajesh Mukthavaam, Santosh Kesari. CT179: A novel small molecule Olig2 inhibitor for the treatment of glioblastoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3030.

Abstract 2357: Therapeutic potential of the natural human IgG1k antibody pritumumab

Pritumumab is a natural human IgG1 kappa antibody derived from a regional draining lymph node of a patient with cervical carcinoma. The recognized antigen is an altered form of vimentin, called ecto-domain vimentin (EDV), that is expressed on the cell surface of epithelial tumor cells. A recombinant version of the mAb was made using the GPEx® system in CHO cells. In a series of comparable studies the CHO mAb was compared with the original hybridoma. Binding specificity with both flow cytometry and immunohistochemical analysis, Western blot analysis, and Antibody-Dependent Cell-Mediated Cytotoxicity (ADCC) activity confirms the comparability of the two versions. A concentration-dependent study of pritumumab-mediated ADCC suggests an EC50 of 39.6ng/ml. Further studies include establishing a xenograft model with both SCID and athymic nude mice in which pritumumab was effective in preventing tumor growth in nude mice but not in SCID mice. Analysis of a blood brain barrier model suggests pritumumab shows minimal distribution in normal brain tissues and significant binding in tumor areas of brain tissues indicating the mAb crosses the tumor brain barrier. Overall, these data together suggest pritumumab is suitable for development as an anti-tumor therapeutic.

Citation Format: Ivan Babic, Rajesh Mukthavaram, Natsuko Nomura, Sandeep Pingle, Mark C. Glassy, Santosh Kesari. Therapeutic potential of the natural human IgG1k antibody pritumumab. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2357.

Abstract 357: Rapid harvesting of highly concentrated circulating tumor cells from bulk human blood with buoyant immuno-microbubbles

Circulating tumor cells (CTCs) are the extremely rare cells shed from primary tumor during metastatic disease. A technology to quickly and inexpensively isolate viable CTCs will enable widespread clinical utilization of CTCs for cancer prognosis and drug testing. The lipid-shelled microbubble is a biocompatible material that has been used as ultrasound contrast media. We have previously shown that MB is a promising vehicle to isolate rare cells from biological fluids by flotation. Here we investigated the role of lipid composition, MB/cell ratio, and type of tumor surface marker [epithelial cell adhesion molecule (EpCAM), receptor tyrosine-protein kinase erbB-2 or human epidermal growth factor receptor 2 (HER2/neu) and epithelial growth factor receptor (EGFR)] on MB stability and binding efficiency to breast cancer cells. Optimized MBs coated with anti-EpCAM antibody showed 95% binding efficiency to human breast carcinoma SKBR-3 cells. Cells were able to proliferate in culture with MBs attached to them. We further developed an inverted setup in order to harvest (skim) highly concentrated tumor cells in a microliter volume on a nitrocellulose membrane. Using vacuum-assisted harvesting we demonstrated a high efficiency (∼80%) of isolation of rare tumor cells spiked in 7 ml blood by anti-EpCAM MBs. A blinded study using anti-EpCAM MBs detected epithelial CTCs in samples of metastatic breast and ovarian cancers with brain metastases, but not in samples from non-epithelial brain malignancies, including primary glioblastoma multiforme, hemangioblastoma and metastatic melanoma. The simple and robust MB approach can be developed into an inexpensive tool for batch CTC isolation in basic research and clinical applications.

Citation Format: Guankui Wang, Sandeep Pingle, Santosh Kesari, Yu-Tsueng Liu, Dmitri Simberg. Rapid harvesting of highly concentrated circulating tumor cells from bulk human blood with buoyant immuno-microbubbles. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 357.

Further understanding of the pathology of glioma: implications for the clinic

INTRODUCTION

Glioma classification and grading has been historically based in morphologic appearance of tumor cells: astrocytomas, oligodendrogliomas, oligoastrocytomas and ependymomas. Recent molecular advances have transformed the field of neuro-oncology, as some molecular markers harbor diagnostic, prognostic and therapeutic implications.

AREAS COVERED

In this paper we will review the major molecular changes associated with gliomas and their implications in diagnosis, prognosis, and opportunities in therapeutics. Expert commentary: Based on current understanding, adult diffuse infiltrating gliomas can be molecularly divided into three to five major subgroups with different clinical outcomes. Pediatric gliomas harbor mutations for H3F3A, ATRX and DAXX but not IDH. Circumscribed low-grade gliomas tend to have BRAF alterations. Clinical behavior of ependymomas correlates more with location than WHO grading. Posterior fossa ependymomas tend to behave worse than their cerebral or spinal cord counterparts. However, with the posterior fossa ependymomas, two distinct subtypes have emerged molecularly.