Rachel C. Blitzblau

A KRAS-Variant in Ovarian Cancer Acts as a Genetic Marker of Cancer Risk

Ovarian cancer (OC) is the single most deadly form of womens cancer, typically presenting as an advanced disease at diagnosis in part due to a lack of known risk factors or genetic markers of risk. The KRAS oncogene and altered levels of the microRNA (miRNA) let-7 are associated with an increased risk of developing solid tumors. In this study, we investigated a hypothesized association between an increased risk of OC and a variant allele of KRAS at rs61764370, referred to as the KRAS-variant, which disrupts a let-7 miRNA binding site in this oncogene. Specimens obtained were tested for the presence of the KRAS-variant from nonselected OC patients in three independent cohorts, two independent ovarian case-control studies, and OC patients with hereditary breast and ovarian cancer syndrome (HBOC) as well as their family members. Our results indicate that the KRAS-variant is associated with more than 25% of nonselected OC cases. Further, we found that it is a marker for a significant increased risk of developing OC, as confirmed by two independent case-control analyses. Lastly, we determined that the KRAS-variant was present in 61% of HBOC patients without BRCA1 or BRCA2 mutations, previously considered uninformative, as well as in their family members with cancer. Our findings strongly support the hypothesis that the KRAS-variant is a genetic marker for increased risk of developing OC, and they suggest that the KRAS-variant may be a new genetic marker of cancer risk for HBOC families without other known genetic abnormalities.

The Glutamate Transport Inhibitor L-trans-pyrrolidine-2,4-dicarboxylate Indirectly Evokes NMDA Receptor Mediated Neurotoxicity in Rat Cortical Cultures

Because of the well‐documented importance of glutamate uptake in protecting neurons against glutamate toxicity, we were interested in testing the effects of L‐trans‐pyrrolidine‐2,4‐ dicarboxylate (PDC) on rat cortical cultures. This compound is a substrate for glutamate transporters and is a potent glutamate transport inhibitor that does not interact significantly with glutamate receptors. Using a 30 min exposure, and assessing neuronal survival after 20‐24 h, PDC was neurotoxic in conventional astrocyte‐rich cortical cultures, with an EC50 in these cultures of 320 ± 157 μM. In astrocyte‐poor cultures, an EC50 for PDC of 50 ± 5 μM was determined. The neurotoxicity of PDC in both astrocyte‐rich and astrocyte‐poor cultures was blocked by the NMDA antagonist MK‐801, but not by the non‐NMDA receptor antagonist 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione (CNQX). We tested the possibility that the neurotoxicity of PDC might be due to release of excitatory amino acids using several approaches. After pre‐loading cells with the non‐metabolizable analogue of glutamate, [3H]‐D‐aspartate, first we demonstrated that PDC caused significant efflux of [3H]‐D‐aspartate. This effect of PDC was dependent upon extracellular sodium. In contrast with glutamate neurotoxicity, PDC neurotoxicity was inhibited by removal of extracellular sodium. In the presence of 1 mM PDC, sodium caused neurotoxicity with an EC50 of 18 ± 7.6 mM. Tetrodotoxin had no effect on either PDC neurotoxicity or on PDC‐evoked [3H]‐D‐aspartate release. PDC‐evoked release of [3H]‐D‐aspartate was demonstrable in astrocyte cultures with no neurons present. PDC also evoked release of endogenous glutamate. Finally, the neurotoxicity of PDC was blocked by coincubation with glutamate‐pyruvate transaminase plus pyruvate to degrade extracellular glutamate. These results demonstrate the neurotoxicity of PDC, and suggest that the mechanism of this toxicity is the glutamate transporter‐dependent accumulation of glutamate in the extracellular space.

Surveillance, Epidemiology, and End Results (SEER) database analysis of microcystic adnexal carcinoma (sclerosing sweat duct carcinoma) of the skin.

Background:Microcystic adnexal carcinoma (MAC) is a very rare cancer of the skin. It has only been described previously in case reports and small retrospective series. Objective:To analyze and summarize data from the National Cancer Institute, Surveillance, Epidemiology, and End Results (SEER) database regarding MAC. Methods:The SEER 1973 to 2004 database was investigated, and patients with MAC were identified. A statistical analysis was performed. Results:Two hundred twenty-three patients were identified. Predominant site of disease was the head and neck skin (74%). There was only 1 case of recorded metastatic disease. Lymph nodes were pathologically involved in 1%. The 10-year overall survival was 86.4% (Standard Error [SE]: 3.3%). US census population-matched relative survival was 97.7% at 10 years (SE: 5.2%). Limitations:This study is limited by the retrospective nature of the SEER database. Conclusions:MAC is locally invasive, and rarely metastasizes to lymph nodes. Overall and population-matched relative survival is excellent.

Receptor targeting and heterogeneity at interneuronal nicotinic cholinergic synapses in vivo

Within a single neuron the correct targeting of the diverse neurotransmitter receptor types to discrete synaptic regions is crucial for proper function. However, the molecular mechanisms that underlie neuronal receptor clustering and targeting are still largely undefined. Here we report advances in defining the mechanisms that mediate nicotinic acetylcholine receptor (nAChR) targeting to interneuronal synapses. Recent in vivo studies have demonstrated that one subunit plays a critical role in the differentiation of nicotinic cholinergic synapses on vertebrate autonomic neurons. The major cytoplasmic loop of the α3 subunit targets specific nAChR subtypes to the synapse. In contrast, nAChR complexes that lack the α3 targeting domain are excluded and are perisynaptic. Additional studies have demonstrated a greater complexity to α3‐nAChR targeting due to a unique postsynaptic receptor microheterogeneity – under one presynaptic terminal, α3‐nAChR clusters are separate, but proximal to, glycine receptor (GlyR) clusters in discrete postsynaptic membrane microregions. The surprising coexistence under one nerve ending of separate clusters of receptors that respond to different fast‐acting transmitters with opposing functions may represent a novel mechanism for modulating synaptic activity. Overall, the receptor targeting and clustering studies reviewed in this issue suggest that a common mechanism underlies the formation of the diverse types of interneuronal synapses but differs from that responsible for neuromuscular junction assembly in vertebrates.

Preoperative Single-Fraction Partial Breast Radiation Therapy: A Novel Phase 1, Dose-Escalation Protocol With Radiation Response Biomarkers.

PURPOSE Women with biologically favorable early-stage breast cancer are increasingly treated with accelerated partial breast radiation (PBI). However, treatment-related morbidities have been linked to the large postoperative treatment volumes required for external beam PBI. Relative to external beam delivery, alternative PBI techniques require equipment that is not universally available. To address these issues, we designed a phase 1 trial utilizing widely available technology to 1) evaluate the safety of a single radiation treatment delivered preoperatively to the small-volume, intact breast tumor and 2) identify imaging and genomic markers of radiation response. METHODS AND MATERIALS Women aged ≥55 years with clinically node-negative, estrogen receptor-positive, and/or progesterone receptor-positive HER2-, T1 invasive carcinomas, or low- to intermediate-grade in situ disease ≤2 cm were enrolled (n=32). Intensity modulated radiation therapy was used to deliver 15 Gy (n=8), 18 Gy (n=8), or 21 Gy (n=16) to the tumor with a 1.5-cm margin. Lumpectomy was performed within 10 days. Paired pre- and postradiation magnetic resonance images and patient tumor samples were analyzed. RESULTS No dose-limiting toxicity was observed. At a median follow-up of 23 months, there have been no recurrences. Physician-rated cosmetic outcomes were good/excellent, and chronic toxicities were grade 1 to 2 (fibrosis, hyperpigmentation) in patients receiving preoperative radiation only. Evidence of dose-dependent changes in vascular permeability, cell density, and expression of genes regulating immunity and cell death were seen in response to radiation. CONCLUSIONS Preoperative single-dose radiation therapy to intact breast tumors is well tolerated. Radiation response is marked by early indicators of cell death in this biologically favorable patient cohort. This study represents a first step toward a novel partial breast radiation approach. Preoperative radiation should be tested in future clinical trials because it has the potential to challenge the current treatment paradigm and provide a path forward to identify radiation response biomarkers.

Analysis of Primary CD30 + Cutaneous Lymphoproliferative Disease and Survival From the Surveillance, Epidemiology, and End Results Database

PURPOSE Primary CD30+ cutaneous lymphoproliferative disease (PCLPD) is a spectrum of indolent cutaneous T-cell lymphomas. The primary intention of the analysis of the National Cancer Institute Surveillance, Epidemiology, and End Results (SEER) database was to report epidemiologic information and overall survival of patients with PCLPD. METHODS We investigated the SEER database from 1973 to 2004 and performed univariable and multivariable survival analysis. RESULTS A total of 268 cases of PCLPD were recorded from 1973 to 2004. Median age at diagnosis was 61 years (range, 5 to 98 years). Among cases, 58% were male, and 42% female. Race distribution was 87% white, 7% black, and 4% Asian/Pacific Islander. A total of 157 patients had primary, localized PCLPD. For the total population (N = 268), overall survival at 3 years was 81% (95% CI, 74% to 87%). Population-matched relative survival at 3 years was 87% (SE, 3.6%). Disease-specific survival at 5 years was 92% (95% CI, 86% to 95%). Head and neck skin site predicted for inferior overall survival in patients with primary, localized PCLPD on univariable analysis (hazard ratio [HR] = 4.4; P = .008; 95% CI, 1.5 to 13.2), and was suggestive of decreased overall survival on multivariate analysis (HR = 3.0; P = .06; 95% CI, 0.95 to 9.7). CONCLUSION Localized PCLPDs are rare diseases with an excellent overall survival and occur more frequently in whites and in men. Head and neck skin primary site may be associated with poorer survival. CONCLUSIONS regarding subsets demonstrating association with survival should be taken with caution, given the small number of deaths analyzed.

Biological Subtype Predicts Risk of Locoregional Recurrence After Mastectomy and Impact of Postmastectomy Radiation in a Large National Database.

PURPOSE To evaluate locoregional recurrence (LRR) after mastectomy and impact of postmastectomy radiation (PMRT) by breast cancer subtype. METHODS AND MATERIALS Between 2000 and 2009, 5673 patients with stage I to III breast carcinoma underwent mastectomy and nodal evaluation; 30% received PMRT. Isolated LRR (iLRR) and LRR were compared across groups defined by biological subtype and receipt of trastuzumab: luminal A (estrogen [ER]/progesterone [PR]+, HER2-, low/intermediate grade), luminal B (ER/PR+, HER2-, high grade), HER2 with trastuzumab, HER2 without trastuzumab, and triple negative (TN; ER-, PR-, HER2-). LRR hazard ratios (HR) were estimated with multivariable Fine and Gray models. The effect of PMRT on LRR was evaluated with Fine and Gray models stratified by propensity for PMRT. RESULTS With a median follow-up time of 50.1 months, there were 19 iLRR and 109 LRR events. HER2 patients with trastuzumab had no iLRR and only a single LRR. Compared with luminal A patients, TN patients had significantly greater adjusted risk of iLRR (HR 14.10; 95% CI 2.97%-66.90%), with a similar trend among luminal B (HR 4.94; 95% CI 0.94%-25.82%) and HER2 patients without trastuzumab (HR 4.41; 95% CI 0.61%-32.11%). Although PMRT reduced LRR, the effect of PMRT varied by subgroup, with the greatest and smallest effects seen among luminal A (HR 0.17; 95% CI 0.05%-0.62%) and TN patients (HR 0.59; 95% CI 0.25%-1.35%), respectively. CONCLUSIONS TN patients had the highest risk of LRR and the least benefit from PMRT; these patients may benefit from alternative treatment strategies. In contrast, in the era of HER2-directed therapy, the role of local therapy may need to be reassessed among HER2 patients.

The use of adjuvant radiotherapy in elderly patients with early-stage breast cancer: changes in practice patterns after publication of Cancer and Leukemia Group B 9343.

The Cancer and Leukemia Group B (CALGB) 9343 randomized phase 3 trial established lumpectomy and adjuvant therapy with tamoxifen alone, rather than both radiotherapy and tamoxifen, as a reasonable treatment course for women aged >70 years with clinical stage I (AJCC 7th edition), estrogen receptor‐positive breast cancer. An analysis of the Surveillance, Epidemiology, and End Results (SEER) registry was undertaken to assess practice patterns before and after the publication of this landmark study.

Comparison of the Potency of Competitive NMDA Antagonists Against the Neurotoxicity of Glutamate and NMDA

Abstract: The object of this investigation was to determine whether glutamate uptake affects the apparent potency of the competitive antagonists dl‐2‐amino‐5‐phosphonovalerate and CGS‐19755 in blocking NMDA receptor‐mediated neurotoxicity. In astrocyte‐rich rat cortical cultures we observed that dl‐2‐amino‐5‐phosphonovalerate and CGS‐19755 were 24 and 16 times more potent against NMDA than against glutamate‐induced toxicity. In contrast, dl‐2‐amino‐5‐phosphonovalerate was equipotent against the two agonists in astrocyte‐poor cultures, in which dendrites are directly exposed to the extracellular medium. With the noncompetitive NMDA antagonist MK‐801, similar potencies were observed against glutamate (212 ± 16 nM) and against NMDA (155 ± 9 nM) neurotoxicity. These results may be explained if we assume that the neuronal cell body is less susceptible than the dendrites to NMDA receptor‐mediated toxicity, and that the action of glutamate in astrocyte‐rich cultures is confined to the cell body. In this case, one would expect that higher concentrations of glutamate would be needed to produce toxicity in astrocyte‐rich cultures, and that higher concentrations of competitive antagonists would be needed to overcome this toxicity. Our observations help explain the pharmacology of the competitive NMDA antagonists against NMDA receptor‐mediated neurotoxicity but also suggest the possibility that, because the cell body and dendrites may be distinct sites for neurotoxicity, they might also involve different mechanisms of toxicity.

Treatment planning technique in patients receiving postmastectomy radiation therapy

Many of the technical subtleties involved in postmastectomy radiation treatment planning will never be addressed in a robust clinical trial setting. However, these issues are faced daily by practicing radiation oncologists with little to guide them in the published literature. The purpose of this study was to survey a small number of breast care providers in both academic and private practice settings on practical aspects of postmastectomy radiation treatment planning. Topics addressed included the use of sophisticated dose-modulation algorithms, hypofractionation, bolus material, and dose-volume histogram (DVH) constraints. Fifty-two people responded to the survey, 50% in academics and 50% in private practice. As expected, wide variation in clinical practice was seen although a few general trends emerged. We include here, with the survey results, a review of the relevant literature for a number of different treatment-related issues. Although the use of postmastectomy radiation therapy is common, literature guiding the reader on technical aspects of delivery is sparse. The data presented here provide a general framework of what is considered acceptable by currently practicing radiation oncologists in many different practice settings.