Chunyu Cai

Directing the Differentiation of Embryonic Stem Cells to Neural Stem Cells

Embryonic stem cells (ESCs) are a potential source of neural derivatives that can be used in stem cell‐based therapies designed to treat neurological disorders. The derivation of specific neuronal or glial cell types from ESCs invariably includes the production of neural stem cells (NSCs). We describe the basic mechanisms of neural induction during vertebrate embryogenesis and how this information helped formulate several protocols used to generate NSCs from ESCs. We highlight the advantages and disadvantages of each approach and review what has been learned about the intermediate stages in the transition from ESC to NSC. Recent data describing how specific growth factors and signaling molecules regulate production of NSCs are described and a model synthesizing this information is presented. Developmental Dynamics 236:3255–3266, 2007.

Hedgehog Serves as a Mitogen and Survival Factor During Embryonic Stem Cell Neurogenesis

Hedgehog (Hh) signaling is involved in a wide range of important biological activities. Within the vertebrate central nervous system, Sonic Hedgehog (Shh) can act as a morphogen or mitogen that regulates the patterning, proliferation, and survival of neural stem cells (NSCs). However, its role in embryonic stem cell (ESC) neurogenesis has not been explored in detail. We have previously shown that Hh signaling is required for ESC neurogenesis. In order to elucidate the underlying mechanism, we utilized the Sox1‐GFP ESC line, which has a green fluorescent protein (GFP) reporter under the control of the Sox1 gene promoter, providing an easy means of detecting NSCs in live cell culture. We show here that ESC differentiation in adherent culture follows the ESC→ primitive ectoderm → neurectoderm transitions observed in vivo. Selective death of the Sox1‐GFP‐negative cells contributes to the enrichment of Sox1‐GFP‐positive NSCs. Interestingly, Shh is expressed exclusively by the NSCs themselves and elicits distinct downstream gene expression in Sox1‐GFP‐positive and ‐negative cells. Suppression of Hh signaling by antagonist treatment leads to different responses from these two populations as well: increased apoptosis in Sox1‐GFP‐positive NSCs and decreased proliferation in Sox1‐GFP‐negative primitive ectoderm cells. Hedgehog agonist treatment, in contrast, inhibits apoptosis and promotes proliferation of Sox1‐GFP‐positive NSCs. These results suggest that Hh acts as a mitogen and survival factor during early ESC neurogenesis, and evidence is presented to support a novel autocrine mechanism for Hh‐mediated effects on NSC survival and proliferation.

Keratinizing-type squamous cell carcinoma of the oropharynx: p16 overexpression is associated with positive high-risk HPV status and improved survival.

It is well established that nonkeratinizing squamous cell carcinoma (SCC) of the oropharynx is causally related to transcriptionally active human papillomavirus (HPV) and has better survival as compared with carcinomas with a keratinizing phenotype (KSCC). Although the great majority of KSCCs are unrelated to HPV, transcriptionally active HPV is detected in a minority of oropharyngeal cases. To date, it has not been established whether the HPV status in KSCC also confers a survival advantage as it does in HPV-related nonkeratinizing SCC. This study compares clinical outcomes between patients with HPV-positive versus HPV-negative oropharyngeal KSCC. Among a total of 54 cases, 7 (13%) were diffusely and strongly positive for p16. HPV E6/E7 RNA was positive in 5 of the 6 (83%) p16-positive cases that were tested and in only 1 of the 47 (2%) p16-negative cases. Only 1 of the 7 (14%) p16-positive patients developed disease recurrence and died in the follow-up period. Kaplan-Meier survival analysis showed significantly better overall and disease-specific survival in the p16-positive than in the p16-negative patients (P=0.01 and 0.046, respectively). These data, although with relatively small patient numbers, suggest that HPV-related SCC in the oropharynx is associated with highly favorable outcomes, regardless of the keratinizing or nonkeratinizing phenotype.

Management of atypical cranial meningiomas, part 1: predictors of recurrence and the role of adjuvant radiation after gross total resection.

BACKGROUND Indications for external beam radiation therapy (EBRT) for atypical meningiomas (AMs) remain unclear. OBJECTIVE To analyze features associated with recurrence in AM patients after gross total resection (GTR) and to assess the relative benefit of EBRT in a retrospective cohort study. METHODS One hundred fifty-one primary AMs after GTR (88 female patients; median follow-up, 45.0 months) were examined for possible predictors of recurrence (age, sex, location, volume, bone involvement, brain invasion). The Fisher exact and Wilcoxon rank-sum tests were used to analyze the association between these predictors and use of EBRT. The impact on recurrence for these predictors and EBRT was analyzed with Kaplan-Meier and Cox regression. RESULTS Of 151 patients, 13 (8.6%) experienced recurrence after GTR (median, 47.0 months). Multivariate analysis identified elevated mitotic index (P = .007) and brain invasion (P = .002) as predictors of recurrence. Larger volume (P = .96) was not associated with recurrence but was more likely to prompt EBRT (P = .001). Recurrences occurred in 11 of 112 with GTR (9.8%; median, 44 months) and 2 of 39 with GTR/EBRT (5.1%; median, 133 months). The 2-, 5-, and 10-year progression-free survival rates after GTR vs GTR/EBRT were 97%, 86%, and 68% vs 100%, 100%, and 78%. Kaplan-Meier analysis demonstrated no difference in progression-free survival or overall survival after GTR vs GTR/EBRT (P = .8, P > .99). CONCLUSION Brain invasion and high mitotic rates may predict recurrence. After GTR of AMs, EBRT appears not to affect progression-free survival and overall survival, suggesting that observation rather than EBRT may be indicated after GTR.

Management of Atypical Cranial Meningiomas, Part 2: Predictors of Progression and the Role of Adjuvant Radiation After Subtotal Resection.

BACKGROUND The efficacies of adjuvant stereotactic radiosurgery (SRS) and external beam radiation therapy (EBRT) for atypical meningiomas (AMs) after subtotal resection (STR) remain unclear. OBJECTIVE To analyze the clinical, histopathological, and radiographic features associated with progression in AM patients after STR. METHODS Fifty-nine primary AMs after STR were examined for predictors of progression, including the impact of SRS and EBRT, in a retrospective cohort study. RESULTS Twenty-seven patients (46%) progressed after STR (median, 30 months). On univariate analysis, spontaneous necrosis positively (hazard ratio = 5.2; P = .006) and adjuvant radiation negatively (hazard ratio = 0.3; P = .009) correlated with progression; on multivariate analysis, only adjuvant radiation remained independently significant (hazard ratio = 0.3; P = .006). SRS and EBRT were associated with greater local control (LC; P = .02) and progression-free survival (P = .007). The 2-, 5-, and 10-year actuarial LC rates after STR vs STR/EBRT were 60%, 34%, and 34% vs 96%, 65%, and 45%. The 2-, 5-, and 10-year actuarial progression-free survival rates after STR vs STR/EBRT were 60%, 30%, and 26% vs 96%, 65%, and 45%. Compared with STR alone, adjuvant radiation therapy significantly improved LC in AMs that lack spontaneous necrosis (P = .003) but did not improve LC in AMs with spontaneous necrosis (P = .6). CONCLUSION Adjuvant SRS or EBRT improved LC of AMs after STR but only for tumors without spontaneous necrosis. Spontaneous necrosis may aid in decisions to administer adjuvant SRS or EBRT after STR of AMs.

Teratocarcinoma formation in embryonic stem cell-derived neural progenitor hippocampal transplants

Embryonic stem cells (ESCs) hold great therapeutic potential due to their ability to differentiate into cells of the three primary germ layers, which can be used to repopulate disease-damaged tissues. In fact, two cell therapies using ESC derivatives are currently in phase I clinical trials. A main concern in using ESCs and their derivatives for cell transplantation is the ability of undifferentiated ESCs to generate tumors in the host. Positive selection steps are often included in protocols designed to generate particular cell types from ESCs; however, the transition from ESC to progenitor cell or terminally differentiated cell is not synchronous, and residual undifferentiated cells often remain. In our transplants of ESC-derived neural progenitors (ESNPs) into the adult mouse hippocampus, we have observed the formation of teratocarcinomas. We set out to reduce teratocarcinoma formation by enrichment of ESNPs using fluorescence-activated cell sorting (FACS) and have found that, although enrichment prior to transplant reduces the overall rate of teratocarcinoma formation, the tumorigenicity of cell batches can vary widely, even after FACS enrichment to as much as 95% ESNPs. Our data suggest that this variability may be due to the percentage of residual ESCs remaining in the transplant cell population and to the presence of pluripotent epiblast-like cells, not previously identified in transplant batches. Our data emphasize the need for stringent characterization of transplant cell populations that will be used for cell replacement therapies in order to reduce the risk of tumor formation.

Simpson Grade I-III Resection of Spinal Atypical (World Health Organization Grade II) Meningiomas is Associated With Symptom Resolution and Low Recurrence

BACKGROUND Because of their rarity, outcomes regarding spinal atypical meningiomas (AMs) remain unclear. OBJECTIVE To describe the recurrence rate and postoperative outcomes after resection of spinal AMs, and to discuss an appropriate resection strategy and adjuvant therapy for spinal AMs. METHODS Data from all patients who presented with spinal AMs to 2 tertiary referral centers between 1998 and 2013 were obtained by chart review. RESULTS From 102 patients with spinal meningioma, 20 AM tumors (7 cervical, 11 thoracic, 2 thoracolumbar) were identified in 18 patients (median age, 50 years [range, 19-75] at time of resection; 11% male; median follow-up, 32 months [range, 1-179] after resection). Before resection, patients had sensory deficits (70%), pain (70%), weakness (60%), ataxia (50%), spasticity (65%), and incontinence (35%). One tumor presented asymptomatically. Simpson grade I, II, III, and IV resection were achieved in 3 (15%), 13 (65%), 2 (10%), and 2 (10%) tumors, respectively. One patient that underwent Simpson grade III resection received adjuvant radiation therapy. After Simpson grade I-III or gross total resection, no tumors recurred (0%; confidence interval, 0%-17.6%). After Simpson grade IV resection, 1 tumor recurred (50%; confidence interval, 1.3%-98.7%). With the exception of 1 patient who had bilateral paraplegia perioperatively, all other patients experienced improvement of preoperative symptoms after surgery (median time, 3.6 months [range, 1-13] after resection). CONCLUSION Despite published cases suggesting an aggressive clinical course for spinal AMs, this series of spinal AMs reports that gross total resection without adjuvant radiation therapy resulted in symptom resolution and low recurrence.

Fatal Human Herpesvirus 6–Associated Encephalitis in Two Boys With Underlying POLG Mitochondrial Disorders

BACKGROUND Human herpesvirus 6 is a significant cause of the febrile illness roseola infantum in young children. Infection with human herpesvirus 6 typically causes a self-limited febrile illness but occasionally is associated with central nervous system manifestations, including febrile seizures and encephalitis. Host factors associated with severe manifestations of human herpesvirus 6-associated neurological disease remain poorly characterized. CASE REPORTS We report two previously healthy young boys with human herpesvirus 6-associated encephalitis who developed a progressive, and ultimately fatal, encephalopathy with refractory movement disorder concurrent with acquisition of acute human herpesvirus 6 infection. Both children were treated with the antiviral ganciclovir without improvement of their neurological symptoms, although quantitative human herpesvirus 6 polymerase chain reaction of cerebrospinal fluid and/or blood confirmed a decline in viral load with treatment. The clinical course in both cases was most consistent with Alpers-Huttenlocher syndrome, given the intractable seizures, developmental regression, and, ultimately, death due to liver and renal failure. In support of this, postmortem analysis identified both children to be compound heterozygous for mutations in the mitochondrial polymerase γ gene, POLG. CONCLUSIONS POLG mutations are associated with Alpers-Huttenlocher syndrome; however, no prior studies have examined the role of acute human herpesvirus 6 infection in these patients presenting with severe neurological disease. It is possible the POLG mutation phenotype was unmasked and/or exacerbated by human herpesvirus 6 infection in these two patients, potentially contributing to a more rapid clinical deterioration. This report provides new insight into a previously unrecognized association between POLG mutations and poor neurological outcome after human herpesvirus 6 infection.

Radiation Therapy for Residual or Recurrent Atypical Meningioma: The Effects of Modality, Timing, and Tumor Pathology on Long-Term Outcomes.

BACKGROUND Optimal use of stereotactic radiosurgery (SRS) vs external beam radiation therapy (EBRT) for treatment of residual/recurrent atypical meningioma is unclear. OBJECTIVE To analyze features associated with progression after radiation therapy. METHODS Fifty radiation-naive patients who received SRS or EBRT for residual and/or recurrent atypical meningioma were examined for predictors of progression using Cox regression and Kaplan-Meier analyses. RESULTS Thirty-two patients (64%) received adjuvant radiation after subtotal resection, 12 patients (24%) received salvage radiation after progression following subtotal resection, and 6 patients (12%) received salvage radiation after recurrence following gross total resection. Twenty-one patients (42%) received SRS (median 18 Gy), and 7 (33%) had tumor progression. Twenty-nine patients (58%) received EBRT (median 54 Gy), and 13 (45%) had tumor progression. Whereas tumor volume (P = .53), SRS vs EBRT (P = .45), and adjuvant vs salvage (P = .34) were not associated with progression after radiation therapy, spontaneous necrosis (hazard ratio [HR] = 82.3, P < .001), embolization necrosis (HR = 15.6, P = .03), and brain invasion (HR = 3.8, P = .008) predicted progression in univariate and multivariate analyses. Tumors treated with SRS/EBRT had 2- and 5-year actuarial locoregional control rates of 91%/88% and 71%/69%, respectively. Tumors with spontaneous necrosis, embolization necrosis, and no necrosis had 2- and 5-year locoregional control rates of 76%, 92%, and 100% and 36%, 73%, and 100%, respectively (P < .001). CONCLUSION This study suggests that necrosis may be a negative predictor of radiation response regardless of radiation timing or modality. ABBREVIATIONS AM, atypical meningiomaEBRT, external beam radiation therapyGTR, gross total resectionLC, locoregional controlOS, overall survivalPOE, preoperative embolizationRT, radiation therapySRS, stereotactic radiosurgerySTR, subtotal resection.

In myofibroblastic sarcomas of the head and neck, mitotic activity and necrosis define grade: a case study and literature review

Low-grade myofibroblastic sarcoma (LGMFS) is considered a distinct entity in the World Health Organization classification of soft tissue neoplasms, defined as an atypical myofibroblastic proliferation with fibromatosis-like features and a predilection for the head and neck. A substantial subset of previously reported myofibroblastic sarcomas (MFS), particularly in the head and neck region, are associated with appreciable tumor-associated morbidity and mortality and should be differentiated from the more indolent LGMFS. However, no specific morphological criteria have been developed to define the entity of LGMFS. We have reviewed histological findings in conjunction with clinical follow-up information of previously reported MFS in the head and neck region in the English literature, with the addition of five new cases from our institution. We found that MFSs with 6 or more mitoses per 10 high power fields and/or presence of spontaneous necrosis were accompanied by a higher mortality rate that is statistically significant.