Purpose: Cancer stem cells (CSC) have been isolated from human tumors, including glioblastoma multiforme (GBM). The aims of this study were the immunobiological characterization of GBM CSCs and the assessment of whether these cells represent suitable targets for immunotherapy. Experimental Design: GBM CSC lines and their fetal bovine serum (FBS)–cultured non-CSC pair lines were generated and examined by flow cytometry for expression of known tumor antigens, MHC-I and MHC-II molecules, antigen-processing machinery components, and NKG2D ligands. In addition, immunogenicity and immunosuppression of such cell lines for autologous or allogeneic T lymphocytes were tested by cytokine secretion (ELISPOT) or proliferation (carboxyfluorescein diacetate succinimidyl ester) assays, respectively. Results: Both GBM CSC and FBS lines were weakly positive and negative for MHC-I, MHC-II, and NKG2D ligand molecules, respectively. Antigen-processing machinery molecules were also defective in both cell types. Upregulation of most molecules was induced by IFNs or 5-Aza deoxycytidine, although more efficiently in FBS than in CSCs. Patient T-cell responses, mediated by both TH1 and the TH2 subsets, against autologous CSC could be induced in vitro. In addition, CSC but not their paired FBS tumor lines inhibited T-cell proliferation of healthy donors. Notably, a differential gene signature that was confirmed at the protein levels for some immunologic-related molecules was also found between CSC and FBS lines. Conclusions: These results indicate lower immunogenicity and higher suppressive activity of GBM CSC compared with FBS lines. The immunogenicity, however, could be rescued by immune modulation leading to anti-GBM T cell–mediated immune response. Clin Cancer Res; 16(3); 800–13

Epidermal growth factor receptor (EGFR) is a known diagnostic and, although controversial, prognostic marker of human glioblastoma multiforme (GBM). However, its functional role and biological significance in GBM remain elusive. Here, we show that multiple GBM cell subpopulations could be purified from the specimens of patients with GBM and from cancer stem cell (CSC) lines based on the expression of EGFR and of other putative CSC markers. All these subpopulations are molecularly and functionally distinct, are tumorigenic, and need to express EGFR to promote experimental tumorigenesis. Among them, EGFR-expressing tumor-initiating cells (TIC) display the most malignant functional and molecular phenotype. Accordingly, modulation of EGFR expression by gain-of-function and loss-of-function strategies in GBM CSC lines enhances and reduces their tumorigenic ability, respectively, suggesting that EGFR plays a fundamental role in gliomagenesis. These findings open up the possibility of new therapeutically relevant scenarios, as the presence of functionally heterogeneous EGFR^pos and EGFR^neg TIC subpopulations within the same tumor might affect clinical response to treatment. Cancer Res; 70(19); 7500–13. ©2010 AACR.

Object: Since the 1990s, Gamma Knife radiosurgery (GKRS) has become the first-line treatment option for small- to medium-size vestibular schwannomas (VSs), especially in patients without mass effect–related symptoms and with functional hearing. The aim of this study was to assess the safety and efficacy of GKRS, in terms of tumor control, hearing preservation, and complications, in a series of 379 consecutive patients treated for VS.Methods: Of 523 patients treated at the authors' institution for VS between 2001 and 2010, the authors included 379 who underwent GKRS as the primary treatment. These patients were not affected by Type 2 neurofibromatosis and had clinical follow-up of at least 36 months. Clinical follow-up (mean and median 75.7 and 69.5 months, respectively) was performed for all patients, whereas audiometric and quantitative radiological follow-up examinations were obtained for only 153 and 219 patients, respectively. The patients' ages ranged from 23 to 85 years (mean 59 years). The mean tumor volume was 1.94 ± 2.2 cm³ (median 1.2 cm³, range 0.013–14.3 cm³), and the median margin dose was 13 Gy (range 11–15 Gy). Parameters considered as determinants of the clinical outcome were long-term tumor control, hearing preservation, and complications. A statistical analysis was performed to correlate clinical outcomes with the radiological features of the tumor, dose-planning parameters, and patient characteristics.Results: Control of the tumor with GKRS was achieved in 97.1% of the patients. In 82.7% of the patients, the tumor volume had decreased at the last follow-up, with a mean relative reduction of 34.1%. The rate of complications was very low, with most consisting of a transient worsening of preexisting symptoms. Patients who had vertigo, balance disorders, or facial or trigeminal impairment usually experienced a complete or at least significant symptom relief after treatment. However, no significant improvement was observed in patients previously reporting tinnitus. The overall rate of preservation of functional hearing at the long-term follow-up was 49%; in patients with hearing classified as Gardner-Robertson (GR) Class I, this value was 71% and reached 93% among cases of GR Class I hearing in patients younger than 55 years.Conclusions: Gamma Knife radiosurgery is a safe and effective treatment for VS, achieving tumor control in 97.1% of cases and resulting in a very low morbidity rate. Younger GR Class I patients had a significantly higher probability of retaining functional hearing even at the 10-year follow-up; for this reason, the time between symptom onset, diagnosis, and treatment should be shortened to achieve better outcomes in functional hearing preservation.

Context: Single-session stereotactic radiotherapy (SR) may be a potential adjuvant treatment in acromegaly. Objective: We analyzed the safety and efficacy of SR in patients who had previously received maximal surgical debulking at our center. Design: The study was a retrospective analysis of hormonal, radiological, and ophthalmologic data collected in a predefined protocol from 1994 through 2006. Setting: The study was performed at a university hospital. Patients: Eighty-three acromegalic patients, 52 women and 31 men, with a mean age of 42.6 ± 1.2 yr, participated in the study. The median follow-up was 69 months (interquartile range 44–107 months). Intervention: The patients were treated with SR for residual or recurrent GH-secreting adenoma. Main Outcome Measure: Normalization of age- and sex-adjusted IGF-I levels together with a basal GH level below 2.5 μg/liter without concomitant GH-suppressive drugs was the goal of therapy. Results: Fifty patients (60.2%) reached the main outcome of the study. The rate of remission was 52.6% at 5 yr [95% confidence interval (CI) 40.6–64.6%]. Another 13 patients (15.7%), who were resistant to somatostatin analogs, were in remission after SR. Multivariate analysis showed that low basal GH and IGF-I levels were associated with a favorable outcome. No serious side effects occurred after SR. The 5-yr cumulative risk of new onset hypogonadism, hypothyroidism, or hypoadrenalism was 3.6% (95% CI 0–8.6%), 3.3% (95% CI 0–7.7%), and 4.9% (95% CI 0–10.4%), respectively. Conclusion: In a highly selected group of acromegalic patients, SR treatment had good efficacy and safety. This may lead to reconsider the role of SR in the therapeutic algorithm of acromegaly.

Object. Radiation therapy diminishes the risk of recurrence of incompletely removed nonfunctioning pituitary adenoma (NPA). The authors evaluated the efficacy and safety of gamma knife surgery (GKS) in patients with residual NPA following surgical debulking of the tumor. Methods. Fifty-four patients, 26 men and 28 women, ranging in age from 29 to 72 years underwent gamma knife treatment. Baseline and follow-up studies involved magnetic resonance imaging, hormone evaluation, and neuroophthalmological examination 6 and 12 months after GKS and at yearly intervals thereafter. The mean follow up after GKS was 41.1 ± 3.1 months. Two of 52 patients undergoing follow up had a recurrence 40 and 49 months after GKS. In both of these patients the treated lesion had reduced in size, but a new lesion appeared in the contralateral side of the sella turcica. The recurrence-free interval at 5 years was 88.2% (95% confidence interval 72.6–100%). Tumor volume decreased from a baseline value of 2.3 ± 0.2 to 1.7 ± 0.2 cm³ at the last follow up (p < 0.001). Twenty-two patients (42.3%) had a 20% or greater reduction in tumor volume. The administered radiation dose had been significantly higher in patients who experienced tumor reduction. Visual function and motility did not deteriorate in any patient. New cases of hypogonadism, hypothyroidism, and hypoadrenalism occurred in 12.5, 8.6, and 2.3%, respectively, of assessable patients at risk. Conclusions. Gamma knife surgery was effective in controlling the growth of residual NPA after previously performed maximal surgical debulking. The major advantage of GKS compared with fractionated radiotherapy seems to be a lower risk of side effects, especially a lower risk of hypopituitarism.