Purpose To identify mediators of glioblastoma anti-angiogenic therapy resistance and target these mediators in xenografts. Experimental Design We performed microarray analysis comparing bevacizumab-resistant glioblastomas (BRGs) to pre-treatment tumors from the same patients. We established novel xenograft models of anti-angiogenic therapy resistance to target candidate resistance mediator(s). Results BRG microarray analysis revealed upregulation versus pre-treatment of receptor tyrosine kinase c-Met, which underwent further investigation because of its prior biologic plausibility as a bevacizumab resistance mediator. BRGs exhibited increased hypoxia versus pre-treatment in a manner correlating with their c-Met upregulation, increased c-Met phosphorylation, and increased phosphorylation of c-Met-activated focal adhesion kinase (FAK) and STAT3. We developed two novel xenograft models of anti-angiogenic therapy resistance. In the first model, serial bevacizumab treatment of an initially responsive xenograft generated a xenograft with acquired bevacizumab resistance, which exhibited upregulated c-Met expression versus pre-treatment. In the second model, a BRG-derived xenograft maintained refractoriness to the MRI tumor vasculature alterations and survival-promoting effects of bevacizumab. Growth of this BRG-derived xenograft was inhibited by a c-Met inhibitor. Transducing these xenograft cells with c-Met shRNA inhibited their invasion and survival in hypoxia, disrupted their mesenchymal morphology, and converted them from bevacizumab-resistant to bevacizumab-responsive. Engineering bevacizumab-responsive cells to express constitutively active c-Met caused these cells to form bevacizumab-resistant xenografts. Conclusion These findings support the role of c-Met in survival in hypoxia and invasion, features associated with anti-angiogenic therapy resistance; and growth and therapeutic resistance of xenografts resistant to anti-angiogenic therapy. Therapeutically targeting c-Met could prevent or overcome anti-angiogenic therapy resistance.

Human induced pluripotent stem cells (iPSCs) hold promise as a source of adult-derived, patient-specific pluripotent cells for use in cell-based regenerative therapies. However, current methods of cell culture are tedious and expensive, and the mechanisms underlying cell proliferation are not understood. In this study, we investigated expression and function of iPSC integrin extracellular matrix receptors to better understand the molecular mechanisms of cell adhesion, survival, and proliferation. We show that iPSC lines generated using Oct-3/4, Sox-2, Nanog, and Lin-28 express a repertoire of integrins similar to that of hESCs, with prominent expression of subunits alpha5, alpha6, alphav, beta1, and beta5. Integrin function was investigated in iPSCs cultured without feeder layers on Matrigel or vitronectin, in comparison to human embryonic stem cells. beta1 integrins were required for adhesion and proliferation on Matrigel, as shown by immunological blockade experiments. On vitronectin, the integrin alphavbeta5 was required for initial attachment, but inhibition of both alphavbeta5 and beta1 was required to significantly decrease iPSC proliferation. Furthermore, iPSCs cultured on vitronectin for 9 passages retained normal karyotype, pluripotency marker expression, and capacity to differentiate in vitro. These studies suggest that vitronectin, or derivatives thereof, might substitute for Matrigel in a more defined system for iPSC culture.

aBBreViatiONS ACTH = adrenocorticotropic hormone; FSH = follicle-stimulating hormone; GH = growth hormone; GnRH = gonadotropin-releasing hormone; IGF-1= insulin-like growth factor-1; LH = luteinizing hormone; NFA = nonfunctional adenoma; T4 = thyroxine; TRH = thyrotropin-releasing hormone; TSH = thyroid-stimulating hormone. SuBmitted October 10, 2014. accepted January 13, 2015. iNclude wheN citiNg Published online August 7, 2015; DOI: 10.3171/2015.1.JNS141543. diSclOSure The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper. * Mr. Jahangiri and Mr. Wagner contributed equally to this work. OBJectiVe The impact of transsphenoidal surgery for nonfunctional pituitary adenomas (NFAs) on preoperative hypopituitarism relative to the incidence of new postoperative endocrine deficits remains unclear. The authors investigated rates of hypopituitarism resolution and development after transsphenoidal surgery. methOdS Over a 5-year period, 305 transsphenoidal surgeries for NFAs performed at The California Center for Pituitary Disorders were retrospectively reviewed. reSultS Patients with preoperative endocrine deficits (n = 153, 50%) were significantly older (mean age 60 vs 54 years; p = 0.004), more frequently male (65% vs 44%; p = 0.0005), and had larger adenomas (2.4 cm vs 2.1 cm; p = 0.02) than patients without preoperative deficits (n = 152, 50%). Of patients with preoperative endocrine deficits, 53% exhibited symptoms. Preoperative deficit rates were 26% for the thyroid axis; 20% and 16% for the male and female reproductive axes, respectively; 13% for the adrenocorticotropic hormone (ACTH)/cortisol axis, and 19% for the growth hormone (GH)/ insulin-like growth factor-1 (IGF-1) axis. Laboratory normalization rates 6 weeks and 6 months after surgery without hormone replacement were 26% and 36% for male and 13% and 13% for female reproductive axes, respectively; 30% and 49% for the thyroid axis; 3% and 3% for the cortisol axis; and 9% and 22% for the IGF-1 axis (p < 0.05). New postoperative endocrine deficits occurred in 42 patients (13.7%). Rates of new deficits by axes were: male reproductive 3% (n = 9), female reproductive 1% (n = 4), thyroid axis 3% (n = 10), cortisol axis 6% (n = 19), and GH/IGF-1 axis 4% (n = 12). Patients who failed to exhibit any endocrine normalization had lower preoperative gland volumes than those who did not (0.24 cm 3 vs 0.43 cm 3 , respectively; p < 0.05). Multivariate analyses revealed that no variables predicted new postoperative deficits or normalization of the female reproductive, cortisol, and IGF-1 axes. However, increased preoperative gland volume and younger age predicted the chances of a patient with any preoperative deficit experiencing normalization of at least 1 axis. Younger age and less severe preoperative hormonal deficit predicted normalization of the thyroid and male reproductive axes (p < 0.05). cONcluSiONS After NFA resection, endocrine normalization rates in this study varied with the horm...

Pituitary surgery is often accompanied by disturbances of osmoregulation, which may result from manipulation or vascular alterations of the neurohypophysis. These disturbances can manifest as postoperative hypernatremia or hyponatremia. Postoperative hypernatremia is typically caused by diabetes insipidus due to deficient antidiuretic hormone (ADH) secretion. Hyponatremia after pituitary surgery is typically due to syndrome of inappropriate antidiuretic hormone secretion (SIADH) and is typically associated with a euvolemic state. There are, however, rare cases of cerebral salt wasting and the associated contraction of extracellular volume that have been reported after pituitary surgery.2 Hyponatremia after pituitary surgery can be profoundly symptomatic with symptoms including headache, dizziness, nausea, and vomiting, which can lead to costly readmissions after otherwise successful elective pituitary surgeries. 3,4,11 Previous studies have suggested tumor size or patient age as risk factors for postoperative hyponatremia after pituitary surgery, 11 but these studies have been based on small sample sizes of 88-150 patients and did not adequately represent the range of typical pathologies operated on during pituitary surgery. Furthermore, prior studies did not focus on the contribution of other factors such as Department of Neurosurgery and California Center for Pituitary Disorders, University of California, San Francisco, CaliforniaObject. Syndrome of inappropriate antidiuretic hormone secretion-induced hyponatremia is a common morbidity after pituitary surgery that can be profoundly symptomatic and cause costly readmissions. The authors calculated the frequency of postoperative hyponatremia after 1045 consecutive operations and determined the efficacy of interventions correcting hyponatremia.Methods. The authors performed a retrospective review of 1045 consecutive pituitary surgeries in the first 946 patients treated since forming a dedicated pituitary center 5 years ago. Patients underwent preoperative and daily inpatient sodium checks, with outpatient checks as needed.Results. Thirty-two patients presented with hyponatremia; 41% of these patients were symptomatic. Postoperative hyponatremia occurred after 165 operations (16%) a mean of 4 days after surgery (range 0-28 days); 19% of operations leading to postoperative hyponatremia were associated with postoperative symptoms (38% involved dizziness and 29% involved nausea/vomiting) and 15% involved readmission for a mean of 5 days (range 1-20 days). In a multivariate analysis including lesion size, age, sex, number of prior pituitary surgeries, surgical approach, pathology, lesion location, and preoperative hypopituitarism, only preoperative hypopituitarism predicted postoperative hyponatremia (p = 0.006). Of patients with preoperative hyponatremia, 59% underwent medical correction preoperatively and 56% had persistent postoperative hyponatremia. The mean correction rates were 0.4 mEq/L/hr (no treatment; n = 112), 0.5 mEq/L/hr (free water restriction; n = 24),...