Stephanie M. Perkins

Novel roles for A-type lamins in telomere biology and the DNA damage response pathway

A‐type lamins are intermediate filament proteins that provide a scaffold for protein complexes regulating nuclear structure and function. Mutations in the LMNA gene are linked to a variety of degenerative disorders termed laminopathies, whereas changes in the expression of lamins are associated with tumourigenesis. The molecular pathways affected by alterations of A‐type lamins and how they contribute to disease are poorly understood. Here, we show that A‐type lamins have a key role in the maintenance of telomere structure, length and function, and in the stabilization of 53BP1, a component of the DNA damage response (DDR) pathway. Loss of A‐type lamins alters the nuclear distribution of telomeres and results in telomere shortening, defects in telomeric heterochromatin, and increased genomic instability. In addition, A‐type lamins are necessary for the processing of dysfunctional telomeres by non‐homologous end joining, putatively through stabilization of 53BP1. This study shows new functions for A‐type lamins in the maintenance of genomic integrity, and suggests that alterations of telomere biology and defects in DDR contribute to the pathogenesis of lamin‐related diseases.

A dual role for A-type lamins in DNA double-strand break repair

A-type lamins are emerging as regulators of nuclear organization and function. Changes in their expression are associated with cancer and mutations are linked to degenerative diseases -laminopathies-. Although a correlation exists between alterations in lamins and genomic instability, the molecular mechanisms remain largely unknown. We previously found that loss of A-type lamins leads to degradation of 53BP1 protein and defective long-range non-homologous end-joining (NHEJ) of dysfunctional telomeres. Here, we determined how loss of A-type lamins affects the repair of short-range DNA double-strand breaks (DSBs) induced by ionizing radiation (IR). We find that lamins deficiency allows activation of the DNA damage response, but compromises the accumulation of 53BP1 at IR-induced foci (IRIF), hindering the fast phase of repair corresponding to classical-NHEJ. Importantly, reconstitution of 53BP1 is sufficient to rescue long-range and short-range NHEJ. Moreover, we demonstrate an unprecedented role for A-type lamins in the maintenance of homologous recombination (HR). Depletion of lamins compromises HR by a mechanism involving transcriptional downregulation of BRCA1 and RAD51 by the repressor complex formed by the Rb family member p130 and E2F4. In line with the DNA repair defects, lamins-deficient cells exhibit increased radiosensitivity. This study demonstrates that A-type lamins promote genomic stability by maintaining the levels of proteins with key roles in DNA DSBs repair by NHEJ and HR. Our results suggest that silencing of A-type lamins by DNA methylation in some cancers could contribute to the genomic instability that drives malignancy. In addition, lamins-deficient tumor cells could represent a good target for radiation therapy.

Radiotherapeutic Management of Cervical Lymph Node Metastases From an Unknown Primary Site

OBJECTIVE To determine whether ipsilateral radiotherapy affects overall survival, cause-specific survival, or local control in patients with a cancer from an unknown primary of the head and neck compared with comprehensive radiotherapy. DESIGN Retrospective medical record review. SETTING Academic tertiary care hospital. PATIENTS The study population comprised 46 patients with cervical metastases from an unknown primary cancer treated with radiotherapy from 1989 through 2008. Median follow-up was 4.6 years. INTERVENTIONS All patients were treated with radiation therapy. Radiotherapy target volumes were categorized as either ipsilateral neck only (IPSI) or comprehensive (COMP), including both the potential mucosal surfaces and ipsilateral or bilateral neck. Human papillomavirus (HPV) status, as determined by p16 immunohistochemical analysis, was evaluated for 36 patients (74%). MAIN OUTCOME MEASURES Overall survival, cause-specific survival, locoregional control, and rate of distant metastases were analyzed. RESULTS Overall survival at 2 years and 5 years was 87% and 77%, respectively. Cause-specific survival at 2 years and 5 years was 89% and 81%, respectively. There were no ipsilateral neck failures. There was no difference in overall survival between patients treated with IPSI or COMP radiation therapy. The contralateral neck was controlled in all patients receiving bilateral neck irradiation and in 95% receiving ipsilateral neck irradiation. Of the 34 patients evaluated with p16 immunohistochemical analysis, results for 16 (47%) were positive. There was a nonsignificant trend toward improved overall survival in p16-positive patients (P = .06). CONCLUSION IPSI radiation therapy demonstrated excellent locoregional control with no adverse effect on disease-free survival or overall survival.

Interdigitating and follicular dendritic cell sarcomas: a SEER analysis.

Objectives: Follicular dendritic cell sarcoma (FDCS) and interdigitating dendritic cell sarcoma (IDCS) are rare neoplasms of dendritic cell origin. Because of the rarity of these diagnoses, optimal management is unclear. Methods: In this study, we reviewed the data on FDCS and IDCS available in the Surveillance, Epidemiology, and End Results database. Fifty-four patients with FDCS and 20 with IDCSs were identified between the years 2001 and 2008. Results: Median follow-up was 28 months. Sixty-one percent of FDCS patients and 55% of IDCS patients presented with localized disease. Of the FDCS patients with localized disease, 31/33 (94%) underwent surgical resection. Fifty-five percent (6/11) of localized IDCS patients underwent surgical resection. Radiation therapy was given to 30% of patients. Overall survival was significantly better for patient with FDCS compared to those with IDCS. Median survival was 35 months in patients with IDCS and was not reached in patients with FDCS. There was a trend toward improved overall survival in FDCS patients with localized disease. IDCS patients with localized disease had a significantly improved overall survival compared with those with distant disease with 2-year overall survival of 72% versus 33%, respectively (P=0.05). Conclusions: These data demonstrate that most patients with localized disease are treated similar to a soft tissue sarcoma with primary surgical resection with or without radiation. No chemotherapy data were available in the Surveillance, Epidemiology, and End Results database. The role of chemotherapy and radiation therapy remains unclear.

BRAF V600E mutational status in pediatric thyroid cancer

Clinical outcome of papillary thyroid carcinoma (PTC) in children differs significantly from that of adults. There is no clear explanation of this difference although previous studies have demonstrated a lower prevalence of the BRAFV600E mutation in PTC of children. However, data are limited due to the rarity of this diagnosis. BRAFV600E mutation prevalence and its relationship with outcome in pediatric PTC remain unclear.

BRAF mutation is not predictive of long‐term outcome in papillary thyroid carcinoma

The BRAF mutation occurs commonly in papillary thyroid carcinoma (PTC). Previous investigations of its utility to predict recurrence‐free survival (RFS) and disease‐specific survival (DSS) have reported conflicting results and its role remains unclear. The purpose of this retrospective study was to determine the incidence of the BRAF mutation and analyze its relationship to clinicopathologic risk factors and long‐term outcomes in the largest, single‐institution American cohort to date. BRAF mutational status was determined in 508 PTC patients using RFLP analysis. The relationships between BRAF mutation status, patient and tumor characteristics, RFS, and DSS were analyzed. The BRAF mutation was present in 67% of patients. On multivariate analysis, presence of the mutation predicted only for capsular invasion (HR, 1.7; 95% CI, 1.1–2.6), cervical lymph node involvement (HR, 1.7; 95% CI, 1.1–2.7), and classic papillary histology (HR, 1.8; 95% CI 1.1–2.9). There was no significant relationship between the BRAF mutation and RFS or DSS, an observation that was consistent across univariate, multivariate, and Kaplan–Meier analyses. This is the most extensive study to date in the United States to demonstrate that BRAF mutation is of no predictive value for recurrence or survival in PTC. We found correlations of BRAF status and several clinicopathologic characteristics of high‐risk disease, but limited evidence that the mutation correlates with more extensive or aggressive disease. This analysis suggests that BRAF is minimally prognostic in PTC. However, prevalence of the BRAF mutation is 70% in the general population, providing the opportunity for targeted therapy.

Subsequent malignancies and their effect on survival in patients with retinoblastoma

As cure rates for retinoblastoma have improved, it is clear that patients with hereditary retinoblastoma experience increased risk of subsequent malignant neoplasms (SMNs).

Treatment Approach, Surveillance, and Outcome of Well-Differentiated Thyroid Cancer in Childhood and Adolescence

BACKGROUND Well-differentiated thyroid carcinoma in children and adolescents is a rare disease with favorable prognosis despite regional and distant metastasis at presentation in many patients. Treatment recommendations are varied and there is little consensus on follow-up guidelines for these patients. METHODS Medical records of patients less than 22 years of age treated at our institution were reviewed. One hundred twelve patients treated between 1969 and 2009 were selected for further analysis. Effects of patient and tumor characteristics on progression-free survival (PFS) were evaluated along with the predictive value of whole-body (131)I scintigraphy in the follow-up setting. RESULTS Overall survival at 20 years and 30 years was 100% and 94.4%, respectively. PFS at 10, 20, and 30 years was 71%, 62%, and 55%, respectively. Although male patients and younger patients presented with more advanced disease, sex, and age at diagnosis had no effect on risk of PFS. Additionally, neither the presence of vascular invasion, capsular extension, positive margins, nor soft tissue invasion had an effect on PFS. Mean time to recurrence in patients who underwent immediate postoperative (131)I therapy was 3.8 years compared to 14.1 years in patients who either never received (131)I therapy or were treated in the salvage setting (p<0.0001). Negative posttreatment whole-body (131)I scintigraphy was strongly predictive for decreased risk of recurrence, especially in patients with three consecutive negative scans. CONCLUSIONS Pediatric patients are more likely to present with advanced disease and for this reason, the majority of patients treated at our institution receive postoperative (131)I. Long-term surveillance is required in this population because of the risk of late recurrences. Whole-body (131)I scintigraphy is useful for risk stratification; after three consecutive negative scans, the risk of recurrence is low.

Outcome for children with metastatic solid tumors over the last four decades.

Background Outcomes for pediatric solid tumors have significantly improved over the last 30 years. However, much of this improvement is due to improved outcome for patients with localized disease. Here we evaluate overall survival (OS) for pediatric patients with metastatic disease over the last 40 years. Procedure The United States Surveillance, Epidemiology, and End Results (SEER) database was used to conduct this study. Patients diagnosed between 0 and 18 years of age with metastatic Ewings sarcoma, neuroblastoma, osteosarcoma, rhabdomyosarcoma or Wilms tumor were included in the analysis. Results 3,009 patients diagnosed between 1973–2010 met inclusion criteria for analysis. OS at 10 years for patients diagnosed between 1973–1979, 1980–1989, 1990–1999 and 2000–2010 was 28.3%, 37.2%, 44.7% and 49.3%, respectively (p<0.001). For patients diagnosed between 2000–2010, 10-year OS for patients with Ewing sarcoma, neuroblastoma, osteosarcoma, rhabdomyosarcoma and Wilms tumor was 30.6%, 54.4%, 29.3%, 27.5%, and 76.6%, respectively, as compared to 13.8%, 25.1%, 13.6%, 17.9% and 57.1%, respectively, for patients diagnosed between 1973–1979. OS for neuroblastoma significantly increased with each decade. For patients with osteosarcoma and Ewing sarcoma, there was no improvement in OS over the last two decades. There was no improvement in outcome for patients with rhabdomyosarcoma or Wilms tumor over the last 30 years. Conclusions OS for pediatric patients with metastatic solid tumors has significantly improved since the 1970s. However, outcome has changed little for some malignancies in the last 20–30 years. These data underscore the importance of continued collaboration and studies to improve outcome for these patients.

Treatment approach and outcomes of vaginal melanoma.

Objective To describe the characteristics of primary vaginal melanoma patients in the Surveillance, Epidemiology, and End Result database and to determine the outcome from the treatment approaches. Materials/Methods From the Surveillance, Epidemiology, and End Result registry, 201 patients with vaginal melanoma were identified. Patients’ characteristics and prognostic factors including age, race, extent of surgery, and use of radiation therapy were obtained. Results The median age was 68 years (range, 28–100 years). The population was 73% white, 11% black, and 16% Asian/American Indian. International Federation of Gynecology and Obstetrics staging results were stage I (46%), stage II (18%), stage III (3%), stage IVA (3%), stage IVB (12%), and unknown (18%). Treatment approach included surgical resection of the primary site in 70%, whereas 35% of the patients underwent lymph node resection. Approximately 40% of the patients received radiotherapy, which was primarily used in the adjuvant setting. Overall survival at 2 and 5 years was 24% and 15%, respectively. Presence of lymph nodes at diagnosis was associated with worse overall survival (hazard ratio, 1.98; P = 0.02). Adjuvant radiation did not offer a statistically significant overall survival advantage compared to surgery alone. Conclusions Vaginal melanoma is a rare diagnosis primarily affecting the elderly. Overall survival is low even for patients presenting with disease limited to the vagina. Lymph node involvement at diagnosis is strongly predictive of worse overall survival. Most patients are treated with surgical resection with varying use of adjuvant radiotherapy. Further research is needed to identify the etiology and improve the outcome of this aggressive disease.