Alfredo Quinones-Hinojosa

Oxygen in Stem Cell Biology: A Critical Component of the Stem Cell Niche

The defining hallmark of stem cells is their ability to self-renew and maintain multipotency. This capacity depends on the balance of complex signals in their microenvironment. Low oxygen tensions (hypoxia) maintain undifferentiated states of embryonic, hematopoietic, mesenchymal, and neural stem cell phenotypes and also influence proliferation and cell-fate commitment. Recent evidence has identified a broader spectrum of stem cells influenced by hypoxia that includes cancer stem cells and induced pluripotent stem cells. These findings have important implications on our understanding of development, disease, and tissue-engineering practices and furthermore elucidate an added dimension of stem cell control within the niche.

Cellular composition and cytoarchitecture of the adult human subventricular zone: A niche of neural stem cells

The lateral wall of the lateral ventricle in the human brain contains neural stem cells throughout adult life. We conducted a cytoarchitectural and ultrastructural study in complete postmortem brains (n = 7) and in postmortem (n = 42) and intraoperative tissue (n = 43) samples of the lateral walls of the human lateral ventricles. With varying thickness and cell densities, four layers were observed throughout the lateral ventricular wall: a monolayer of ependymal cells (Layer I), a hypocellular gap (Layer II), a ribbon of cells (Layer III) composed of astrocytes, and a transitional zone (Layer IV) into the brain parenchyma. Unlike rodents and nonhuman primates, adult human glial fibrillary acidic protein (GFAP)+ subventricular zone (SVZ) astrocytes are separated from the ependyma by the hypocellular gap. Some astrocytes as well as a few GFAP‐cells in Layer II in the SVZ of the anterior horn and the body of the lateral ventricle appear to proliferate based on proliferating cell nuclear antigen (PCNA) and Ki67 staining. However, compared to rodents, the adult human SVZ appears to be devoid of chain migration or large numbers of newly formed young neurons. It was only in the anterior SVZ that we found examples of elongated Tuj1+ cells with migratory morphology. We provide ultrastructural criteria to identify the different cells types in the human SVZ including three distinct types of astrocytes and a group of displaced ependymal cells between Layers II and III. Ultrastructural analysis of this layer revealed a remarkable network of astrocytic and ependymal processes. This work provides a basic description of the organization of the adult human SVZ. J. Comp. Neurol. 494:415–434, 2006.

Mesoporous Silica-Coated Hollow Manganese Oxide Nanoparticles as Positive T1 Contrast Agents for Labeling and MRI Tracking of Adipose-Derived Mesenchymal Stem Cells

Mesoporous silica-coated hollow manganese oxide (HMnO@mSiO2) nanoparticles were developed as a novel T1 magnetic resonance imaging (MRI) contrast agent. We hypothesized that the mesoporous structure of the nanoparticle shell enables optimal access of water molecules to the magnetic core, and consequently, an effective longitudinal (R1) relaxation enhancement of water protons, which value was measured to be 0.99 (mM−1s−1) at 11.7 T. Adipose-derived mesenchymal stem cells (MSCs) were efficiently labeled using electroporation, with much shorter T1 values as compared to direct incubation without electroporation, which was also evidenced by signal enhancement on T1-weighted MR images in vitro. Intracranial grafting of HMnO@mSiO2-labeled MSCs enabled serial MR monitoring of cell transplants over 14 days. These novel nanoparticles may extend the arsenal of currently available nanoparticle MR contrast agents by providing positive contrast on T1-weighted images at high magnetic field strengths.

Extent of surgical resection is independently associated with survival in patients with hemispheric infiltrating low-grade gliomas

OBJECTIVEIt remains unknown whether the extent of surgical resection affects survival or disease progression in patients with supratentorial low-grade gliomas. METHODSWe conducted a retrospective cohort study (n = 170) between 1996 and 2007 at a single institution to determine whether increasing extent of surgical resection was associated with improved progression-free survival (PFS) and overall survival (OS). Surgical resection of gliomas defined as gross total resection (GTR) (complete resection of the preoperative fluid-attenuated inversion recovery signal abnormality), near total resection (NTR) (<3-mm thin residual fluid-attenuated inversion recovery signal abnormality around the rim of the resection cavity only), or subtotal resection (STR) (residual nodular fluid-attenuated inversion recovery signal abnormality) based on magnetic resonance imaging performed less than 48 hours after surgery. Our main outcome measures were OS, PFS, and malignant degeneration-free survival (conversion to high-grade glioma). RESULTSOne hundred thirty-two primary and 38 revision resections were performed for low-grade astrocytomas (n = 93) or oligodendrogliomas (n = 77). GTR, NTR, and STR were achieved in 65 (38%), 39 (23%), and 66 (39%) cases, respectively. GTR versus STR was independently associated with increased OS (hazard ratio, 0.36; 95% confidence interval, 0.16–0.84; P = 0.017) and PFS (HR, 0.56; 95% confidence interval, 0.32–0.98; P = 0.043) and a trend of increased malignant degeneration-free survival (hazard ratio, 0.46; 95% confidence interval, 0.20–1.03; P = 0.060). NTR versus STR was not independently associated with improved OS, PFS, or malignant degeneration-free survival. Five-year OS after GTR, NTR, and STR was 95, 80, 70%, respectively, and 10-year OS was 76, 57, and 49%, respectively. After GTR, NTR, and STR, median time to tumor progression was 7.0, 4.0, and 3.5 years, respectively. Median time to malignant degeneration after GTR, NTR, and STR was 12.5, 5.8, and 7 years, respectively. CONCLUSIONGTR was associated with a delay in tumor progression and malignant degeneration as well as improved OS independent of age, degree of disability, histological subtype, or revision versus primary resection. GTR should be safely attempted when not limited by eloquent cortex.

Establishing percent resection and residual volume thresholds affecting survival and recurrence for patients with newly diagnosed intracranial glioblastoma

INTRODUCTION Surgery is first-line therapy for glioblastoma, and there is evidence that gross total resection is associated with improved survival. Gross total resection, however, is not always possible, and relationships among extent (percent) of resection (EOR), residual volume (RV), and survival are unknown. The goals were to evaluate whether there is an association between EOR and RV with survival and recurrence and to establish minimum EOR and maximum RV thresholds. METHODS Adult patients who underwent primary glioblastoma surgery from 2007 to 2011 were retrospectively reviewed. Three-dimensional volumetric tumor measurements were made. Multivariate proportional hazards regression analysis was used to evaluate the relationship between EOR and RV with survival and recurrence. RESULTS Of 259 patients, 203 (78%) died and 156 (60%) had tumor recurrence. The median survival and progression-free survival were 13.4 and 8.9 months, respectively. The median (interquartile range) pre- and postoperative tumor volumes were 32.2 (14.0-56.3) and 2.1 (0.0-7.9) cm(3), respectively. EOR was independently associated with survival (hazard ratio [HR], 0.995; 95% confidence interval [CI]: 0.990-0.998; P = .008) and recurrence (HR [95% CI], 0.992 [0.983-0.998], P = .005). The minimum EOR threshold for survival (P = .0006) and recurrence (P = .005) was 70%. RV was also associated with survival (HR [95% CI], 1.019 [1.006-1.030], P = .004) and recurrence (HR [95% CI], 1.024 [1.001-1.044], P = .03). The maximum RV threshold for survival (P = .01) and recurrence (P = .01) was 5 cm(3). CONCLUSION This study shows for the first time that both EOR and RV are significantly associated with survival and recurrence, where the thresholds are 70% and 5 cm(3), respectively. These findings may help guide surgical and adjuvant therapies aimed at optimizing outcomes for glioblastoma patients.

c-Met signaling induces a reprogramming network and supports the glioblastoma stem-like phenotype

The tyrosine kinase c-Met promotes the formation and malignant progression of multiple cancers. It is well known that c-Met hyperactivation increases tumorigenicity and tumor cell resistance to DNA damaging agents, properties associated with tumor-initiating stem cells. However, a link between c-Met signaling and the formation and/or maintenance of neoplastic stem cells has not been previously identified. Here, we show that c-Met is activated and functional in glioblastoma (GBM) neurospheres enriched for glioblastoma tumor-initiating stem cells and that c-Met expression/function correlates with stem cell marker expression and the neoplastic stem cell phenotype in glioblastoma neurospheres and clinical glioblastoma specimens. c-Met activation was found to induce the expression of reprogramming transcription factors (RFs) known to support embryonic stem cells and induce differentiated cells to form pluripotent stem (iPS) cells, and c-Met activation counteracted the effects of forced differentiation in glioblastoma neurospheres. Expression of the reprogramming transcription factor Nanog by glioblastoma cells is shown to mediate the ability of c-Met to induce the stem cell characteristics of neurosphere formation and neurosphere cell self-renewal. These findings show that c-Met enhances the population of glioblastoma stem cells (GBM SCs) via a mechanism requiring Nanog and potentially other c-Met–responsive reprogramming transcription factors.

Regulation of glioblastoma stem cells by retinoic acid: role for Notch pathway inhibition

It is necessary to understand mechanisms by which differentiating agents influence tumor-initiating cancer stem cells. Toward this end, we investigated the cellular and molecular responses of glioblastoma stem-like cells (GBM-SCs) to all-trans retinoic acid (RA). GBM-SCs were grown as non-adherent neurospheres in growth factor supplemented serum-free medium. RA treatment rapidly induced morphology changes, induced growth arrest at G1/G0 to S transition, decreased cyclin D1 expression and increased p27 expression. Immunofluorescence and western blot analysis indicated that RA induced the expression of lineage-specific differentiation markers Tuj1 and GFAP and reduced the expression of neural stem cell markers such as CD133, Msi-1, nestin and Sox-2. RA treatment dramatically decreased neurosphere-forming capacity, inhibited the ability of neurospheres to form colonies in soft agar and inhibited their capacity to propagate subcutaneous and intracranial xenografts. Expression microarray analysis identified ∼350 genes that were altered within 48 h of RA treatment. Affected pathways included retinoid signaling and metabolism, cell-cycle regulation, lineage determination, cell adhesion, cell–matrix interaction and cytoskeleton remodeling. Notch signaling was the most prominent of these RA-responsive pathways. Notch pathway downregulation was confirmed based on the downregulation of HES and HEY family members. Constitutive activation of Notch signaling with the Notch intracellular domain rescued GBM neurospheres from the RA-induced differentiation and stem cell depletion. Our findings identify mechanisms by which RA targets GBM-derived stem-like tumor-initiating cells and novel targets applicable to differentiation therapies for glioblastoma.

Surgical outcomes for older patients with glioblastoma multiforme: preoperative factors associated with decreased survival. Clinical article.

OBJECT As the population ages, the incidence of glioblastoma multiforme (GBM) among older patients (age > 65 years) will increase. Older patients, unlike their younger counterparts, are not often offered aggressive surgery because of their age, comorbidities, and potential inability to tolerate surgery. The goal of this study was to identify preoperative factors associated with decreased survival for older patients who underwent resection of a GBM. The identification of these factors may provide insight into which patients would benefit most from aggressive surgery. METHODS All patients older than 65 years who underwent nonbiopsy resection of an intracranial GBM at a single institution between 1997 and 2007 were retrospectively reviewed. Factors associated with overall survival were assessed using multivariate proportional hazards regression analysis after controlling for peri- and postoperative factors known to be associated with outcome (extent of resection, carmustine wafer implantation, temozolomide chemotherapy, and radiation therapy). Variables with p < 0.05 were considered statistically significant. RESULTS A total of 129 patients with an average age of 73 ± 5 years met the inclusion/exclusion criteria. At last follow-up, all 129 patients had died, with a median survival of 7.9 months. The preoperative factors that were independently associated with decreased survival were Karnofsky Performance Scale (KPS) score less than 80 (p = 0.001), chronic obstructive pulmonary disease (p = 0.01), motor deficit (p = 0.01), language deficit (p = 0.005), cognitive deficit (p = 0.02), and tumor size larger than 4 cm (p = 0.002). Patients with 0-1 (Group 1), 2-3 (Group 2), and 4-6 (Group 3) of these factors had statistically different survival times, where the median survival was 9.2, 5.5, and 4.4 months, respectively. In log-rank analysis, the median survival for Group 1 was significantly longer than that for Group 2 (p = 0.004) and Group 3 (p < 0.0001), while Group 2 had longer survival than Group 3 (p = 0.02). CONCLUSIONS Older patients with an increasing number of these factors may not benefit as much from aggressive surgery as patients with fewer factors. This may provide insight into identifying which patients older than 65 years of age may benefit from aggressive surgery.

Recurrence and malignant degeneration after resection of adult hemispheric low-grade gliomas.

OBJECT Unlike their malignant counterparts, low-grade gliomas are associated with prolonged survival. However, these tumors have a propensity to progress after resection and ultimately undergo malignant degeneration. The factors associated with recurrence and malignant degeneration remain relatively unknown. The authors set out to determine factors that were independently associated with recurrence and malignant degeneration in patients who underwent resection of a hemispheric low-grade glioma. METHODS Adult patients who underwent craniotomy and resection of a hemispheric low-grade glioma (WHO Grade II) at the Johns Hopkins Medical Institutions academic tertiary-care institution between 1996 and 2006 were retrospectively reviewed. Multivariate proportional hazards regression analyses were used to identify associations with tumor recurrence and malignant degeneration. RESULTS Of the 191 consecutive patients with low-grade gliomas in this series (89 fibrillary astrocytomas, 89 oligodendrogliomas, and 13 mixed gliomas), 83 (43%) and 44 (23%) experienced tumor recurrence and malignant degeneration at last follow-up, respectively. The 5-year progression-free and malignancy-free survival rates were 44 and 74%, respectively. Independent predictors of recurrence were duration of longest lasting symptom (relative risk [RR] 0.978, 95% CI 0.954-0.996, p = 0.01), tumor size (RR 1.328, 95% CI 1.109-1.602, p = 0.002), and preoperative contrast enhancement (RR 2.558, 95% CI 1.241-5.021, p = 0.01). Independent factors associated with malignant degeneration were fibrillary astrocytoma pathology (RR 1.800, 95% CI 1.008-4.928, p = 0.04), tumor size (RR 1.086, 95% CI 1.044-1.358, p = 0.04), and gross-total resection (RR 0.526, 95% CI 0.221-1.007, p = 0.05). CONCLUSIONS The identification and consideration of factors associated with recurrence and malignant progression may help guide treatment strategies aimed at delaying recurrence and preventing malignant degeneration for patients with hemispheric low-grade gliomas.

Biodegradable Polymeric Nanoparticles Show High Efficacy and Specificity at DNA Delivery to Human Glioblastoma in Vitro and in Vivo

Current glioblastoma therapies are insufficient to prevent tumor recurrence and eventual death. Here, we describe a method to treat malignant glioma by nonviral DNA delivery using biodegradable poly(β-amino ester)s (PBAEs), with a focus on the brain tumor initiating cells (BTICs), the tumor cell population believed to be responsible for the formation of new tumors and resistance to many conventional therapies. We show transfection efficacy of >60% and low biomaterial-mediated cytotoxicity in primary human BTICs in vitro even when the BTICs are grown as 3-D oncospheres. Intriguingly, we find that these polymeric nanoparticles show intrinsic specificity for nonviral transfection of primary human BTICs over primary healthy human neural progenitor cells and that this specificity is not due to differences in cellular growth rate or total cellular uptake of nanoparticles. Moreover, we demonstrate that biodegradable PBAE/DNA nanoparticles can be fabricated, lyophilized, and then stored for at least 2 years without losing efficacy, increasing the translational relevance of this technology. Using lyophilized nanoparticles, we show transgene expression by tumor cells after intratumoral injection into an orthotopic murine model of human glioblastoma. PBAE/DNA nanoparticles were more effective than naked DNA at exogenous gene expression in vivo, and tumor cells were transfected more effectively than noninvaded brain parenchyma in vivo. This work shows the potential of nonviral gene delivery tools to target human brain tumors.