Neoplastic Cellularity Assessment in Molecular Testing

CONTEXT.—

Neoplastic cellularity assessment has become an essential component of molecular oncology testing; however, there are currently no best practice recommendations or guidelines for this potentially variable step in the testing process.

OBJECTIVE.—

To describe the domestic and international practices of neoplastic cellularity assessment and to determine how variations in laboratory practices affect neoplastic cellularity assessment accuracy.

DESIGN.—

Data were derived from 57 US and international laboratories that participated in the 2019 College of American Pathologists Neoplastic Cellularity Proficiency Testing Survey (NEO-B 2019). NEO-B 2019 included 29 laboratory practice questions and 5 images exhibiting challenging histologic features. Participants assessed the neoplastic cellularity of hematoxylin-eosin-stained digital images, and results were compared to a criterion standard derived from a manual cell count.

RESULTS.—

The survey responses showed variations in the laboratory practices for the assessment of neoplastic cellularity, including the definition of neoplastic cellularity, assessment methodology, counting practices, and quality assurance practices. In some instances, variation in laboratory practice affected neoplastic cellularity assessment performance.

CONCLUSIONS.—

The results highlight the need for a consensus definition and improved standardization of the assessment of neoplastic cellularity. We put forth an initial set of best practice recommendations to begin the process of standardizing neoplastic cellularity assessment.

Proficiency Testing of Standardized Samples Shows Very High Interlaboratory Agreement for Clinical Next-Generation Sequencing-Based Oncology Assays

CONTEXT.—

Next-generation sequencing-based assays are being increasingly used in the clinical setting for the detection of somatic variants in solid tumors, but limited data are available regarding the interlaboratory performance of these assays.

OBJECTIVE.—

To examine proficiency testing data from the initial College of American Pathologists (CAP) Next-Generation Sequencing Solid Tumor survey to report on laboratory performance.

DESIGN.—

CAP proficiency testing results from 111 laboratories were analyzed for accuracy and associated assay performance characteristics.

RESULTS.—

The overall accuracy observed for all variants was 98.3%. Rare false-negative results could not be attributed to sequencing platform, selection method, or other assay characteristics. The median and average of the variant allele fractions reported by the laboratories were within 10% of those orthogonally determined by digital polymerase chain reaction for each variant. The median coverage reported at the variant sites ranged from 1922 to 3297.

CONCLUSIONS.—

Laboratories demonstrated an overall accuracy of greater than 98% with high specificity when examining 10 clinically relevant somatic single-nucleotide variants with a variant allele fraction of 15% or greater. These initial data suggest excellent performance, but further ongoing studies are needed to evaluate the performance of lower variant allele fractions and additional variant types.

Clinical Validation of a Novel Commercial Reverse Transcription–Quantitative Polymerase Chain Reaction Screening Assay for Detection of ALK Translocations and Amplifications in Non–Small Cell Lung Carcinomas

Context.— EGFR mutations and anaplastic lymphoma kinase (ALK) translocations have significant biologic and therapeutic implications in lung cancers, particularly lung adenocarcinomas. ALK translocations are less frequent compared with EGFR mutations; interestingly, these two abnormalities are most commonly mutually exclusive. The 2013 College of American Pathologists/Association for Molecular Pathology/International Association for the Study of Lung Cancer molecular testing guideline for lung cancers recommend a testing algorithm in which detection of ALK translocations using fluorescence in situ hybridization (FISH) is to be performed following testing for EGFR mutations. Such an algorithm is cost-effective but potentially slows down turnaround time; and as a secondary test, ALK FISH assay may not be completed because it requires the use of additional tissue, and the small biopsies or cytology specimens may have been exhausted in the extraction of nucleic acid for EGFR mutation screening.

Objective.—To provide efficient testing of both EGFR and ALK genetic alterations in small biopsies and cytology specimens.

Design.—We validated a highly sensitive ALK reverse transcription–quantitative polymerase chain reaction (RT-qPCR) assay as a screening tool for ALK translocations and amplifications.

Results.—We performed a retrospective review of cases previously tested by FISH and found that all FISH ALK translocation–positive specimens were RT-qPCR positive, and all FISH ALK translocation–negative cases were RT-qPCR negative (the sensitivity and specificity of the ALK RT-qPCR assay were 100%).

Conclusion.—This assay allows rapid identification of ALK alterations, can be performed in conjunction with EGFR testing, and does not require use of valuable additional tumor tissue.

Next-Generation Sequencing of Matched Primary and Metastatic Rectal Adenocarcinomas Demonstrates Minimal Mutation Gain and Concordance to Colonic Adenocarcinomas

CONTEXT

-Colorectal carcinoma is the third most common cause of cancer death in males and females in the United States. Rectal adenocarcinoma can have distinct therapeutic and surgical management from colonic adenocarcinoma owing to its location and anatomic considerations.

OBJECTIVE

-To determine the oncologic driver mutations and better understand the molecular pathogenesis of rectal adenocarcinoma in relation to colon adenocarcinoma.

DESIGN

-Next-generation sequencing was performed on 20 cases of primary rectal adenocarcinoma with a paired lymph node or solid organ metastasis by using an amplicon-based assay of more than 2800 Catalogue of Somatic Mutations in Cancer (COSMIC)-identified somatic mutations.

RESULTS

-Next-generation sequencing data were obtained on both the primary tumor and metastasis from 16 patients. Most rectal adenocarcinoma cases demonstrated identical mutations in the primary tumor and metastasis (13 of 16, 81%). The mutations identified, listed in order of frequency, included TP53, KRAS, APC, FBXW7, GNAS, FGFR3, BRAF, NRAS, PIK3CA, and SMAD4.

CONCLUSIONS

-The somatic mutations identified in our rectal adenocarcinoma cohort showed a strong correlation to those previously characterized in colonic adenocarcinoma. In addition, most rectal adenocarcinomas harbored identical somatic mutations in both the primary tumor and metastasis. These findings demonstrate evidence that rectal adenocarcinoma follows a similar molecular pathogenesis as colonic adenocarcinoma and that sampling either the primary or metastatic lesion is valid for initial evaluation of somatic mutations and selection of possible targeted therapy.

Next-Generation Sequencing of a Cohort of Pulmonary Large Cell Carcinomas Reclassified by World Health Organization 2015 Criteria

CONTEXT

The classification of pulmonary large cell carcinoma has undergone a major revision with the recent World Health Organization (WHO) 2015 Classification. Many large cell carcinomas are now reassigned to either adenocarcinoma with solid pattern or nonkeratinizing squamous cell carcinoma based on immunopositivity for adenocarcinoma markers or squamous cell carcinoma markers, respectively. Large cell carcinomas that are negative for adenocarcinoma and squamous cell carcinoma immunomarkers are now classified as large cell carcinoma with null immunohistochemical features (LCC-N). Although a few studies investigated the mutation profile of large cell carcinomas grouped by immunostain profile before the publication of the new WHO classification, investigation of tumors previously diagnosed as large cell carcinoma and reclassified according to the 2015 WHO classification has not, to our knowledge, been reported.

OBJECTIVE

To determine the mutation profiles of pulmonary large cell carcinomas reclassified by WHO 2015 criteria.

DESIGN

Archival cases of non-small cell lung carcinoma with large cell carcinoma morphology (n = 17) were reclassified according to 2015 WHO criteria. To determine mutation profile, we employed Ion Torrent (Life Technologies, Carlsbad, California)-based next-generation sequencing (50 genes; more than 2800 mutations) in addition to real-time quantitative reverse transcription polymerase chain reaction for ALK translocation detection.

RESULTS

Two of 17 cases (12%) were reclassified as LCC-N, and both had mutations-BRAF D594N in one case and KRAS G12C in the other case. Seven of 17 cases (41%) were reclassified in the adenocarcinoma with solid pattern group, which showed one KRAS G12C and one EGFR E709K + G719C double mutation in addition to mutations in TP53. Eight of 17 cases (47%) were reclassified in the nonkeratinizing squamous cell carcinoma group, which showed mutations in PIK3CA, CDKN2A, and TP53. No ALK translocations or amplifications were detected.

CONCLUSIONS

The adenocarcinoma with solid pattern group showed mutations typical of adenocarcinoma, whereas the nonkeratinizing squamous cell carcinoma group showed mutations typical of squamous cell carcinoma. Both LCC-N cases had mutations associated with adenocarcinoma, supporting the hypothesis that LCC-N is related to adenocarcinoma.

Genomic microarray analysis on formalin-fixed paraffin-embedded material for uveal melanoma prognostication

Cytogenetic alterations are strong outcome prognosticators in uveal melanoma (UVM). Monosomy 3 (-3) and MYC amplification at 8q24 are commonly tested by fluorescence in situ hybridization (FISH). Alternatively, microarray analysis provides whole genome data, detecting partial chromosome loss, loss of heterozygosity (LOH), or abnormalities unrepresented by FISH probes. Nonfixed frozen tissue is conventionally used for microarray analysis but may not always be available. We assessed the feasibility of genomic microarray analysis for high resolution interrogation of UVM using formalin-fixed paraffin-embedded tissue (FFPET) as an alternative to frozen tissue (FZT). Enucleations from 44 patients (clinical trial NCT00952939) yielded sufficient DNA from FFPET (n = 34) and/or frozen tissue (n = 41) for comparative genomic hybridization and select single nucleotide polymorphism analysis (CGH/SNP) on Roche-NimbleGen OncoChip arrays. CEP3 FISH analysis was performed on matched cytology ThinPrep material. CGH/SNP analysis was successful in 30 of 34 FFPET and 41 of 41 FZT samples. Of 27 paired FFPET/FZT samples, 26 (96.3%) were concordant for at least four of six major recurrent abnormalities (-3, +8q, -1p, +6p, -6q, -8p), and 25 of 27 (92.6%) were concordant for -3. Results of CGH/SNP were concordant with the CEP3 FISH results in 27 of 30 (90%) FFPET and 38 of 41 (92.6%) FZT cases; partial -3q was detected in two CEP3 FISH-negative cases and whole chromosome 3, 4, and 6 SNP-LOH in one case. CGH detection of -3, +8q, -8p on FFPET and FZT showed significant correlation with the clinical outcome measures (metastasis development, time to progression, survival). Results of the UVM genotyping by CGH/SNP on FFPET are highly concordant with those of the FZT analysis and with those of the CEP3 FISH analysis, and therefore CGH/SNP is a practical method for UVM prognostication. Genome-wide coverage provides additional data with potential relevance to UVM biology, diagnosis, and prognosis.

BET protein antagonist JQ1 is synergistically lethal with FLT3 tyrosine kinase inhibitor (TKI) and overcomes resistance to FLT3-TKI in AML cells expressing FLT-ITD

Recently, treatment with bromodomain and extraterminal protein antagonist (BA) such as JQ1 has been shown to inhibit growth and induce apoptosis of human acute myelogenous leukemia (AML) cells, including those expressing FLT3-ITD. Here, we demonstrate that cotreatment with JQ1 and the FLT3 tyrosine kinase inhibitor (TKI) ponatinib or AC220 synergistically induce apoptosis of cultured and primary CD34(+) human AML blast progenitor cells (BPC) expressing FLT3-ITD. Concomitantly, as compared with each agent alone, cotreatment with JQ1 and the FLT3-TKI caused greater attenuation of c-MYC, BCL2, and CDK4/6. Simultaneously, cotreatment with JQ1 and the FLT3-TKI increased the levels of p21, BIM, and cleaved PARP, as well as mediated marked attenuation of p-STAT5, p-AKT, and p-ERK1/2 levels in AML BPCs. Conversely, cotreatment with JQ1 and FLT3-TKI was significantly less active against CD34(+) normal bone marrow progenitor cells. Knockdown of BRD4 by short hairpin RNA also sensitized AML cells to FLT3-TKI. JQ1 treatment induced apoptosis of mouse Ba/F3 cells ectopically expressing FLT3-ITD with or without FLT3-TKI-resistant mutations F691L and D835V. Compared with the parental human AML FLT3-ITD-expressing MOLM13, MOLM13-TKIR cells resistant to AC220 were markedly more sensitive to JQ1-induced apoptosis. Furthermore, cotreatment with JQ1 and the pan-histone deacetylase inhibitor (HDI) panobinostat synergistically induced apoptosis of FLT3-TKI-resistant MOLM13-TKIR and MV4-11-TKIR cells. Collectively, these findings support the rationale for determining the in vivo activity of combined therapy with BA and FLT3-TKI against human AML cells expressing FLT3-ITD or with BA and HDI against AML cells resistant to FLT3-TKI.

HER4 expression status correlates with improved outcome in both neoadjuvant and adjuvant Trastuzumab treated invasive breast carcinoma

Prognostic and predictive markers utilized in invasive breast carcinoma are limited and include ER, PR, Ki67, and ERBB2 (HER2). In the case of HER2, over-expression or amplification serves as eligibility for anti-HER2 based therapy, including trastuzumab (Herceptin®, Genentech). While clinical trials have shown trastuzumab improves overall survival and time to progression, an individual's response to anti-HER2 based therapy is highly variable. This suggests that, in a “uniform” HER2 positive population, additional markers could help in predicting patient outcome to therapy. Here we utilized a recently validated high-specificity HER4 antibody (E200) and generated a standard clinical HER4 scoring algorithm (HER4 H-Score) utilizing two breast carcinoma cohorts: 1) patients receiving neoadjuvant trastuzumab (n=47) and 2) patients receiving trastuzumab for metastatic disease (n=33). Our HER4 H-Score showed significant correlation with high sensitivity RT-qPCR performed on matched patients (p=<0.0001). In addition, patients with HER2/HER4 co-over-expression status showed a significant delay in development of metastasis after neo-adjuvant trastuzumab therapy (p= 0.04) and showed a significant improvement in progression free survival after adjuvant trastuzumab therapy (p=0.03). These findings suggest HER4 IHC, used in conjunction with a standard HER2 testing algorithm, could aid in predicting clinical outcome and help identify patients likely to show improved response to trastuzumab therapy.

Highly active combination of BRD4 antagonist and histone deacetylase inhibitor against human acute myelogenous leukemia cells

The bromodomain and extra-terminal (BET) protein family members, including BRD4, bind to acetylated lysines on histones and regulate the expression of important oncogenes, for example, c-MYC and BCL2. Here, we demonstrate the sensitizing effects of the histone hyperacetylation-inducing pan-histone deacetylase (HDAC) inhibitor panobinostat on human acute myelogenous leukemia (AML) blast progenitor cells (BPC) to the BET protein antagonist JQ1. Treatment with JQ1, but not its inactive enantiomer (R-JQ1), was highly lethal against AML BPCs expressing mutant NPM1c+ with or without coexpression of FLT3-ITD or AML expressing mixed lineage leukemia fusion oncoprotein. JQ1 treatment reduced binding of BRD4 and RNA polymerase II to the DNA of c-MYC and BCL2 and reduced their levels in the AML cells. Cotreatment with JQ1 and the HDAC inhibitor panobinostat synergistically induced apoptosis of the AML BPCs, but not of normal CD34(+) hematopoietic progenitor cells. This was associated with greater attenuation of c-MYC and BCL2, while increasing p21, BIM, and cleaved PARP levels in the AML BPCs. Cotreatment with JQ1 and panobinostat significantly improved the survival of the NOD/SCID mice engrafted with OCI-AML3 or MOLM13 cells (P < 0.01). These findings highlight cotreatment with a BRD4 antagonist and an HDAC inhibitor as a potentially efficacious therapy of AML.

Highly effective combination of LSD1 (KDM1A) antagonist and pan-histone deacetylase inhibitor against human AML cells

The histone demethylase LSD1 (KDM1A) demethylates mono- and di-methylated (Me2) lysine (K) 4 on histone H3. High LSD1 expression blocks differentiation and confers a poor prognosis in AML. Here, treatment with the novel LSD1 antagonist SP2509 attenuated the binding of LSD1 with the co-repressor CoREST, increased the permissive H3K4Me3 mark on the target gene promoters, and increased the levels of p21, p27 and C/EBPα in cultured AML cells. Additionally, SP2509 treatment or LSD1 shRNA inhibited the colony growth of AML cells. SP2509 also induced morphologic features of differentiation in the cultured and primary AML blasts. SP2509 induced more apoptosis of AML cells expressing mutant NPM1 than MLL fusion oncoproteins. Treatment with SP2509 alone significantly improved the survival of immune-depleted mice following tail-vein infusion and engraftment of cultured or primary human AML cells. Co-treatment with pan-HDAC inhibitor (HDI) panobinostat (PS) and SP2509 was synergistically lethal against cultured and primary AML blasts. Compared to each agent alone, co-treatment with SP2509 and PS significantly improved the survival of the mice engrafted with the human AML cells, without exhibiting any toxicity. Collectively, these findings show that the combination of LSD1 antagonist and pan-HDI is a promising therapy warranting further testing against AML.

Quantitative assessment of mutant allele burden in solid tumors by semiconductor-based next-generation sequencing

OBJECTIVES

Identification of tumor-specific somatic mutations has had a significant impact on both disease diagnosis and therapy selection. The ability of next-generation sequencing (NGS) to provide a quantitative assessment of mutant allele burden, in numerous target genes in a single assay, provides a significant advantage over conventional qualitative genotyping platforms.

METHODS

We assessed the quantitative capability of NGS and a primer extension-based matrix-assisted laser desorption ionization-time-of-flight (PE-MALDI) assay and directly correlated NGS mutant allele burden determination to morphologic assessment of tumor percentage in H&E-stained slides.

RESULTS

Our results show a 100% concordance between NGS and PE-MALDI in mutant allele detection and a significant correlation between NGS and PE-MALDI for determining mutant allele burden when mutant allele burden is 10% or more.

CONCLUSIONS

NGS-based mutation screening provides a quantitative assessment comparable to that of PE-MALDI. In addition, NGS also allows for a high degree of multiplexing and uses nanogram quantities of DNA, thereby preserving precious material for future analysis. Furthermore, this study provides evidence that H&E-based morphologic assessment of tumor burden does not correlate to actual tumor mutant allele burden frequency.

Next-generation sequencing-based multi-gene mutation profiling of solid tumors using fine needle aspiration samples: promises and challenges for routine clinical diagnostics

Increasing use of fine needle aspiration for oncological diagnosis, while minimally invasive, poses a challenge for molecular testing by traditional sequencing platforms due to high sample requirements. The advent of affordable benchtop next-generation sequencing platforms such as the semiconductor-based Ion Personal Genome Machine (PGM) Sequencer has facilitated multi-gene mutational profiling using only nanograms of DNA. We describe successful next-generation sequencing-based testing of fine needle aspiration cytological specimens in a clinical laboratory setting. We selected 61 tumor specimens, obtained by fine needle aspiration, with known mutational status for clinically relevant genes; of these, 31 specimens yielded sufficient DNA for next-generation sequencing testing. Ten nanograms of DNA from each sample was tested for mutations in the hotspot regions of 46 cancer-related genes using a 318-chip on Ion PGM Sequencer. All tested samples underwent successful targeted sequencing of 46 genes. We showed 100% concordance of results between next-generation sequencing and conventional test platforms for all previously known point mutations that included BRAF, EGFR, KRAS, MET, NRAS, PIK3CA, RET and TP53, deletions of EGFR and wild-type calls. Furthermore, next-generation sequencing detected variants in 19 of the 31 (61%) patient samples that were not detected by traditional platforms, thus increasing the utility of mutation analysis; these variants involved the APC, ATM, CDKN2A, CTNNB1, FGFR2, FLT3, KDR, KIT, KRAS, MLH1, NRAS, PIK3CA, SMAD4, STK11 and TP53 genes. The results of this study show that next-generation sequencing-based mutational profiling can be performed on fine needle aspiration cytological smears and cell blocks. Next-generation sequencing can be performed with only nanograms of DNA and has better sensitivity than traditional sequencing platforms. Use of next-generation sequencing also enhances the power of fine needle aspiration by providing gene mutation results that can direct personalized cancer therapy.

Abstract P1-02-05: Identification of HER-2/neu amplification using amplicon based benchtop next generation sequencing

Introduction

Aplicon based next generation sequencing (NGS) assays have the potential to incorporate simultaneous assessment of somatic mutations and copy number variation into a single platform. Although not specifically designed for this purpose, we noted numerous examples of apparent HER-2/neu gene amplification in analyzing results from our mutation profiling 46-gene cancer NGS panel (Life Technologies, South San Francisco, CA).

Material and Methods

Existing amplicon coverage data from the TorrentSuite 2.0 (Life Technologies) pipeline was accessed and used to generate a HER-2/neu coverage proportion (ratio between all HER-2/neu amplicon reads and all other amplicon reads). This ratio was calculated for 170 unique cases of breast carcinoma. A total of 4 cases were eliminated from analysis due to indeterminate IHC/FISH results. Using a total of 166 cases, we performed ROC curve analysis to determine the sensitivity and specificity of NGS based HER-2/neu amplification compared to that of traditional IHC and FISH testing (MedCalc v8.0).

Results

The NGS based HER-2/neu coverage proportions in the 166 cases showed a clearly non-normal distribution with an outlier cluster of cases with an elevated NGS HER-2/neu ratio (6 cases with ratios &gt;0.045). The distribution of NGS based HER-2/neu ratios for the entire population ranged from 0.01 to a maximum of 0.34. ROC curve analysis of NGS HER-2/neu proportions compared to IHC/FISH data showed a maximal sensitivity of 75.0% and specificity of 100% at an NGS ratio cut off of ≥0.045.

In the 166 cases, 6 showed a HER-2/neu coverage proportion of &gt; 0.045 (range 0.045-0.34). Utilizing the 0.045 NGS ratio cut off value, the population frequency of cases positive for HER2 expression was 3.4%. Of the 160 samples with NGS coverage proportion &lt; 0.045, only two cases were positive by IHC/FISH testing.

The correlation between NGS HER-2/neu coverage proportion and IHC/FISH testing was highly significant (Spearman rank correlation r = 0.67, p &lt; 0.0001 CI: 0.58-0.75).

Conclusions

Even utilizing a limited somatic cancer panel that includes less than 200 amplicons in 46 genes, clinically significant HER-2/neu amplification can be readily identified. This is the first study to describe the functional utility of HER-2/neu amplification detection using a NGS based amplicon assay. This study shows that in addition to mutation analysis, amplification data can be simultaneously obtained, which has striking implications for potential clinical utility and HER-2/neu amplification detection outside of traditional IHC and HER2 testing modalities. Furthermore, utilizing this assay as a primary screening modality could limit the additional expense of multiple single gene testing.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-02-05.

Abstract P1-02-04: Array based resolution of HER2 amplification status in breast carcinomas displaying apparent chromosome 17 aneusomy

Background:

Molecular inversion probe (MIP) arrays offer high-quality copy number and genotype data with whole-genome coverage and high resolution of cancer related genes. The MIP array assay is specifically designed for use with Formalin Fixed Paraffin Embedded (FFPE) tissue due to its design which utilizes hybridization of short sequence inversion probes. In this study, we performed MIP array analysis on a cohort of breast carcinomas with putative chromosome 17 aneusomy identified by HER2/CEP17 dual probe FISH. We hypothesized that MIP array performed on cases with chromosome 17 aneusomy would allow HER2 amplification status resolution and provide additional clinically actionable data on genes with predictive and prognostic significance.

Design:

DNA was extracted from formalin fixed paraffin embedded tissue (Qiagen,Valencia, CA) from invasive breast carcinomas following macrodisection. Breast carcinomas utilized in this study segregated into three groups: 1) Aneusomic 2) Monosomic, and 3) Eusomic cases as determined by FISH utilizing a centromere 17 reference probe (PathVysion; Abbott Molecular). Matched patient normal lymph nodes were performed for a subset of cases from each group. MIP-array data was collected using the Affymetrix OncoScan™ array (Affymetrix, Santa Clara, CA). Analysis of array data was performed using Nexus software v6 (BioDiscovery, Inc., Hawthorne, CA).

Result:

Array-based detection of HER2 amplification in aneusomic breast carcinomas showed 100% concordance with single probe (HER2) FISH. However, based on genomic profiling, these cases showed great variability in regions of aneusomy along chromosome 17. In our aneusomic cohort, one region of chromosome 17 showed conserved eusomy status. This region was utilized for both array and FISH based ratio to resolve HER2 amplification status in 18 of 22 (82%) of cases. In addition to HER2 status resolution by MIP array, gains and losses in genes involved in modulating therapy were also identified, using this single assay.

Conclusion:

Use of MIP array-based genotyping as a single reflex assay in breast carcinomas with apparent chromosome 17 aneusomy resulted in HER2 amplification status resolution. In addition, use of this assay in our aneusomic cohort resulted in identification of a highly conserved region of chromosome 17 that is highly resistant to gains or losses in ploidy. The “D17S122” region was confirmed by FISH and use of a HER2/D17S122 ratio, allowed resolution of HER2 amplification status. In addition to HER2 status resolution and copy number data, MIP Array also provided comprehensive genomic coverage for analysis of non EGFR family genes potentially important for prognosis and therapy response prediction.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-02-04.

Ultrasensitive RNA in situ hybridization for detection of restricted clonal expression of low-abundance immunoglobulin light chain mRNA in B-cell lymphoproliferative disorders

OBJECTIVES

To assess the feasibility of using a novel ultrasensitive bright-field in situ hybridization approach (BRISH) to evaluate κ and λ immunoglobulin messenger RNA (mRNA) expression in situ in B-cell non-Hodgkin lymphoma (NHL).

METHODS

A series of 110 semiconsecutive clinical cases evaluated for lymphoma with historic flow cytometric (FCM) results were assessed with BRISH.

RESULTS

BRISH light chain restriction (LCR) results were concordant with FCM in 108 (99%) of 109 evaluable cases. Additional small B-cell lymphoma cohorts were successfully evaluated.

CONCLUSIONS

BRISH analysis of κ and λ immunoglobulin mRNA expression is a sensitive tool for establishing LCR in B-cell NHL when FCM results are not available.

Immunotherapy of CD30-expressing lymphoma using a highly stable ssDNA aptamer

CD30 is highly expressed on Hodgkins lymphoma and anaplastic large cell lymphoma, making it an attractive target for therapy. We describe the generation of serum-stabilized ssDNA aptamers that bind CD30 via a hybrid SELEX methodology. The selected aptamer bound CD30 with high affinity and specificity. Further optimization of the aptamer led to a short, truncated variant with a 50-fold higher affinity than its longer counterpart. The multivalent aptamer was able to induce oligomerization of CD30 receptors and, in effect, activate downstream signaling, which led to apoptosis of ALCL cells. Immunotherapy using aptamer-based co-stimulation provides an alternative to antibodies, and has potential to transform cancer treatment.

ALK status testing in non-small cell lung carcinoma: correlation between ultrasensitive IHC and FISH

ALK gene rearrangements in advanced non-small cell lung carcinomas (NSCLC) are an indication for targeted therapy with crizotinib. Fluorescence in situ hybridization (FISH) using a recently approved companion in vitro diagnostic class FISH system commonly assesses ALK status. More accessible IHC is challenged by low expression of ALK-fusion transcripts in NSCLC. We compared ultrasensitive automated IHC with FISH for detecting ALK status on 318 FFPE and 40 matched ThinPrep specimens from 296 patients with advanced NSCLC. IHC was concordant with FFPE-FISH on 229 of 231 dual-informative samples (31 positive and 198 negative) and with ThinPrep-FISH on 34 of 34 samples (5 positive and 29 negative). Two cases with negative IHC and borderline-positive FFPE-FISH (15% and 18%, respectively) were reclassified as concordant based on negative matched ThinPrep-FISH and clinical data consistent with ALK-negative status. Overall, after including ThinPrep-FISH and amending the false-positive FFPE-FISH results, IHC demonstrated 100% sensitivity and specificity (95% CI, 0.86 to 1.00 and 0.97 to 1.00, respectively) for ALK detection on 249 dual-informative NSCLC samples. IHC was informative on significantly more samples than FFPE-FISH, revealing additional ALK-positive cases. The high concordance with FISH warrants IHC's routine use as the initial component of an algorithmic approach to clinical ALK testing in NSCLC, followed by reflex FISH confirmation of IHC-positive cases.

Automated quantitative RNA in situ hybridization for resolution of equivocal and heterogeneous ERBB2 (HER2) status in invasive breast carcinoma

Patient management based on HER2 status in breast carcinoma is an archetypical example of personalized medicine but remains hampered by equivocal testing and intratumoral heterogeneity. We developed a fully automated, quantitative, bright-field in situ hybridization technique (RNAscope), applied it to quantify single-cell HER2 mRNA levels in 132 invasive breast carcinomas, and compared the results with those by real-time quantitative PCR (qPCR) and Food and Drug Administration-approved methods, including fluorescence in situ hybridization (FISH), IHC, chromogenic in situ hybridization, and dual in situ hybridization. Both RNAscope and qPCR were 97.3% concordant with FISH in cases in which FISH results were unequivocal. RNAscope was superior to qPCR in cases with intratumoral heterogeneity or equivocal FISH results. This novel assay may enable ultimate HER2 status resolution as a reflex test for current testing algorithms. Quantitative in situ RNA measurement at the single-cell level may be broadly applicable in companion diagnostic applications.

Delay to formalin fixation 'cold ischemia time': effect on ERBB2 detection by in-situ hybridization and immunohistochemistry

The American Society of Clinical Oncology/College of American Pathologists ERBB2 testing guidelines address several pre-analytical variables known to affect ERBB2 testing accuracy. According to 2010 updated guidelines, the pre-analytical variable of time to tissue fixation (cold ischemia time) should be kept to <1 h, however, little has been published about cold ischemia time and its significance in ERBB2 testing. To that end, this study evaluated ERBB2 status using two different FDA-approved in-situ hybridization methods and an FDA-approved immunohistochemistry (IHC) assay in the largest cohort to date (n=84) of invasive breast carcinomas with tracked cold ischemia time. Cold ischemia time was stratified into four groups (<1 h (n=45), 1-2 h (n=27), 2-3 h (n=6), and >3 h (n=6)) and ERBB2 status was evaluated in each group by IHC (4B5) and by in-situ hybridization methodologies (PathVysion(®) fluorescence in situ hybridization and the INFORM HER2(®) dual in situ DNA probe assay). Both in-situ hybridization methods were evaluated using three ERBB2 scoring criteria (dual-probe guidelines, single-probe guidelines, and the FDA package insert scoring instructions). Fluorescence in-situ hybridization (FISH) and INFORM HER2(®) demonstrated 100% concordance in the detection of ERBB2 amplification by all three scoring guidelines at all cold ischemia time points. Agreement between in-situ hybridization methodologies and IHC was superior using single-probe guidelines compared with dual probe or FDA scoring instructions. In addition, Inform HER2(®) in-situ hybridization signals were significantly more intense than FISH at all cold ischemia time points, however, no significant loss of either chromosome 17 or ERBB2 signal was detected by FISH or Inform HER2(®) in-situ hybridization in cold ischemia times up to 3 h. On the basis of our findings, cold ischemia time up to 3 h has no deleterious effect on the detection of ERBB2 via in-situ hybridization or IHC.

Abstract PD02-04: Automated Quantitative RNA In Situ Hybridization for Resolution of Equivocal and Heterogeneous ERBB2 (HER2) Status in Invasive Breast Carcinoma

Background: Breast carcinomas that demonstrate a heterogeneous ERBB2 (HER2) status or equivocal results by both immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) present diagnostic challenges for which there is neither a standard methodology to achieve resolution in the clinical laboratory nor a uniform approach to management. We assessed the feasibility of using a novel automated and quantitative HER2 mRNA bright field in situ hybridization (ISH) assay capable of single molecule detection to determine HER2 status in invasive breast carcinomas that demonstrated significant tumor heterogeneity or failed to be resolved by standard IHC and FISH algorithmic testing.

Design: Formalin-fixed, paraffin-embedded (FFPE) breast carcinomas from a non-consecutive series of 163 patients were analyzed for HER2 mRNA using a fully automated bright field RNA ISH assay (RNAscope, Advanced Cell Diagnostics, Hayward, CA). Cases were assigned into either a training set (n = 34) or a validation set (n = 129) and analyzed by both Q-RT-PCR and RNAscope. automated image analysis was used to numerate the punctate signal dots per cell in RNAscope-stained slides. A HER2 mRNA score based on single-cell quantification by RNAscope was developed and correlated to HER2 FISH and HER2 mRNA Q-RT-PCR results. A simple cutoff value was derived using the training set and applied to the validation set.

Results: Evaluable HER2 results were obtained for 154 cases (94.5%) by RNAscope and 163 cases (100%) by Q-RT-PCR. In the training set, both FISH/IHC positive and negative cases were definitively separated by both Q-RT-PCR and RNAscope. HER2 mRNA dots per cell correlated strongly to FISH (Spearman r=0.77) and Q-RT-PCR (r = 0.81). Application of both methods to the validation set resulted in correct identification of 31/31 positive cases and 41/43 negative (overall concordance=97.3%) for both RNAscope and Q-RT-PCR. RNAscope showed a significant advantage over Q-RT-PCR in correctly identifying cases equivocal by FISH that were resolved by reflex IHC testing. RNAscope classified 7 of 26 (26.9%) FISH/IHC double equivocal cases as positives. In cases with HER2 protein heterogeneity, RNAscope showed a 100% concordance with FISH results, whereas Q-RT-PCR showed a 42.9% concordance.

Conclusion: RNAscope analysis of HER2 mRNA is an effective means to resolve HER2 status in double equivocal cases and cases that demonstrate heterogeneity. Automation and image analysis-based quantification minimize analytical and post-analytical variability. Quantification of single RNA transcripts in situ at single-cell level demonstrates superiority over qRTPCR and great potential in predictive biomarker analysis. Further studies of larger cohorts correlating clinical response with HER2 mRNA expression in situ are warranted.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr PD02-04.

Abstract P6-07-45: Molecular Morphology Based Genomic Signatures of Moderate Complexity Predict Pathologic Complete Response in HER2 Molecular Breast Carcinoma Class Patients Treated with Trastuzumab-based Preoperative Therapy

Background: Preoperative chemotherapy is an effective approach for “downstaging” some breast cancer patients, some of whom achieve a pathologic complete response (pCR), especially for non-luminal B HER2 positive molecular class (HNL). Determination of which HNL patients are more or not likely to achieve pCR would allow a more personalized, predictive approach to neoadjuvant management.

Methods and Materials: Formalin-fixed biopsy specimens from 34 patients with invasive ductal carcinoma treated with trastuzumab-based therapy prior to definitive resection and pathologic staging were evaluated by dual color dual hapten bright field in situ hybridization (dual ISH) using repeat depleted locus specific probes (designation based on the name of a gene included within the targeted region) and a reference centromeric locus probe (CEN) on the same chromosome. Probe pairs included MET+CEN7, TOP2A+CEN17, PTEN+CEN10, and PIK3CA+CEN3. Only invasive carcinoma tumor cells were scored. In addition to assessing genomic gains and losses by the average number of gene loci or centromeres per cell and the ratio of gene loci to CEN, the percentage of cells with &gt;2 gene or CEN signals (gene locus gain or CEN gain), &lt;2 signals (gene locus loss or CEN loss), gene locus signals &gt; CEN signals (gene locus/CEN gain), and gene locus signals &lt; CEN signals (gene locus/CEN loss) were calculated for each parameter and cut point. The percentage of cells with either gene locus/CEN gain or loss was also evaluated. Sensitivities and specificities for detecting patients with pCR, based on either the high parameter being positive for pCR, and conversely based on the low parameter being positive for pCR, were calculated for each parameter and each cutoff. Receiver Operator Characteristics (ROC) curves were generated as sensitivity versus 1-specificity over all cutoffs tested, and Area Under the Curve (AUC) was calculated as one measure of a parameter's ability to distinguish patients with pCR from patients without pCR, with AUC = 1 being ideal and progressively lower values being less favorable. 2×2 contingency tables were evaluated at each cutoff to provide chi square probabilities as another measure of a parameter's ability to differentiate patients with pCR. Combinations of parameters were also evaluated by ROC and contingency table analyses.

Results: MET/CEN7 gain or loss was predictive of pCR (AUC = 0.824, N=24) achieving 100% sensitivity and 69% specificity at a cutoff of 50% (X2 p &lt; 0.00089). Combining this parameter with PIK3CA/CEN3 gain provided further improvement (AUC 0.937, N=24) with 89% sensitivity and 93% specificity achieved at respective cutoffs of 50 and 55%.

Conclusion: Genomic signatures of moderate complexity generated from dual ISH evaluation of invasive breast carcinoma predict pathologic complete response in HER2 molecular class breast carcinoma patients treated with trastuzumab-based preoperative therapy. These findings require validation in additional patient cohorts.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P6-07-45.

Diagnosis of BK viral nephropathy in the renal allograft biopsy: role of fluorescence in situ hybridization

Early recognition of BK viral nephropathy is essential for successful management. Our aim in this study was to evaluate a novel fluorescence in situ hybridization (FISH) assay for detection of BK virus in renal transplant biopsies in the context of standard detection methods. Renal allograft biopsies (n = 108) were analyzed via H&E, immunohistochemistry (IHC) for simian virus 40, and FISH for BK virus. BK virus was detected in 16 (14.8%) cases by H&E, 13 (12%) cases by IHC, 18 (16.6%) cases by FISH, and 19 (17.6%) cases by real-time PCR; 24 of 108 showed a discrepancy in ≥1 testing modalities. Comparison of H&E, IHC, and FISH showed no statistical difference in detection of BK virus. However, performing comparisons between the different tissue-based assays in the context of plasma or urine real-time PCR results showed significant improvement in detection of BK by FISH over H&E (P = 0.02) but not IHC (P = 0.07). This novel FISH-based approach for BK virus identification in renal allograft biopsy tissue mirrored real-time PCR results and showed superior performance to detection of inclusions by H&E. Therefore, use of FISH for BK virus detection in the setting of renal allograft biopsy is a useful and sensitive detection method and could be adopted in any laboratory that currently performs FISH analysis.

Use of HER2 score correction for putative chromosome 17 (Chr-17) aneusomy to increase eligibility for anti-HER2 therapy

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Background: HER2 amplification or overexpression status directs therapy choice in breast carcinoma. HER2/Chr-17 ratio is commonly assessed by fluorescence in-situ hybridization (FISH) using a CEP17 centromeric reference probe and ASCO/CAP scoring criteria. However, α-centromeric reference probes may underestimate true HER2 status in cases with para-centromeric amplification. Here we present comprehensive algorithmic testing of an alternative Chr-17 reference locus for resolution of putative CEP17-aneusomic cases in a consecutive series, within a single health system. Methods: 150 of 1256 consecutive breast carcinoma cases accessioned in 2011 within the Cleveland Clinic Health System displayed a mean CEP17 copy number greater than 3.0 by FISH (aneusomy). The patients were reflex-HER2 tested by FISH with a reference probe for the D17S122 locus (17p12) and a corrected HER2/Chr-17 ratio was calculated. Cases with equivocal HER2/D17S122 ratio (1.8-2.2) were further reflex tested for HER2 overexpression by immunohistochemistry (IHC). Results: Of 117 initially non-amplified cases by HER2/CEP17, 20 (17%) were revised to amplified and 18 (15.3%) to equivocal by HER2/D17S122. Of 3 initially equivocal cases, 1 was revised to amplified and 1 remained equivocal. Of the 19 equivocal cases by HER2/D17S122, 3 were revised to positive by IHC. Overall, for CEP17 aneusomic cases tested using this algorithmic approach, 24 of 120 (20%) patients with initial non-amplified or equivocal HER2 status became eligible for anti-HER2-based therapy, which was also considered in 10 equivocal cases with a HER2/D17S122 ratio of 2.0 - 2.2. A significantly lower proportion of initially amplified cases was revised as non-amplified by HER2/D17S122 (1 of 30, 3.3%, p<0.05). Conclusions: Our data, collected within a single health system for a consecutive case series, underscores the clinical limitations of commonly used FISH probes for HER2 testing and demonstrates that algorithmic use of a non-centromeric Chr-17 reference probe alters HER2 status and increases eligibility for anti-HER2 based therapy in a significant proportion of patients.

From morphologic to molecular: established and emerging molecular diagnostics for breast carcinoma

Diagnostics in the field of breast carcinoma are constantly evolving. The recent wave of molecular methodologies, both microscope and non-microscope based, have opened new ways to gain insight into this disease process and have moved clinical diagnostics closer to a 'personalized medicine' approach. In this review we highlight some of the advancements that laboratory medicine technology is making toward guiding the diagnosis, prognosis, and therapy selection for patients affected by breast carcinoma. The content of the article is largely structured by methodology, with a distinct emphasis on both microscope based and non-microscope based diagnostic formats. Where possible, we have attempted to emphasize the potential benefits as well as limitations to each of these technologies. Successful molecular diagnostics, applied in concert within the morphologic context of a patient's tumor, are what will lay the foundation for personalized therapy and allow a more sophisticated approach to clinical trial stratification. The future of breast cancer diagnostics looks challenging, but it is also a field of great opportunity. Never before have there been such a plethora of new tools available for disease investigation or candidate therapy selection.

P1-07-05: HER2 Status Resolution in FISH and IHC “Double Equivocal” Breast Carcinomas by Quantitative Real-Time PCR

Background: Clinical testing for HER2 amplification/over-expression is performed by immunohistochemistry (IHC) and/or fluorescence in situ hybridization (FISH) as outlined by the ASCO/CAP guidelines. Although these guidelines standardize testing and reporting, in a subset of patients, HER2 is equivocal by both IHC and FISH (“Double Equivocal”). These double equivocal patients represent a clinically problematic sub-group that currently lack standardized management guidelines. In this study, we utilize Quantitative Real-Time PCR (Q-RT-PCR) to resolve HER2 status in invasive breast cancer cases that could not be resolved via IHC and FISH testing.

Material and Methods: FISH for HER2 was performed on 2259 invasive breast carcinomas from 1/2008 to 12/2010. In accordance with ASCO/CAP, all equivocal HER2 FISH cases were reflex tested by IHC. In double equivocal cases, RNA extraction was performed following macro-dissection using High Pure RNA Paraffin Kit (Roche Applied Biosciences, Indianapolis, IN). Q-RT-PCR was carried out using TaqMan® RNA-to-CT™ 1-Step Kit with primers and probes for HER2, B2M, and GAPDH (Applied Biosystems, Foster City, CA). Q-RT-PCR results were expressed as the relative quantification of HER2 vs. two control genes, all normalized against calibrator RNA from the MCF7 cell line. Cut off for Q-RT-PCR HER2 overexpression was set using ROC curve analysis (MedCalc, Belgium).

Results: In our cohort of 2259 patients, 124 (5.5%) had an equivocal HER2 result by primary FISH testing. Reflex HER2 testing by IHC was unable to resolve the HER2 status in 35 (1.5%) patients. Detection of HER2 overexpression by Q-RT-PCR was validated using 50 FISH confirmed amplified and 50 non-amplified cases. Q-RT-PCR performed on these 2 control populations generated two non-overlapping populations and ROC curve analysis using a cut off value of 7.0 showed 100% sensitivity and specificity in detection of HER2 overexpression. Application of Q-RT-PCR in the double equivocal sub-group resulted in resolution of HER2 status in all cases, 8 HER2 positive (test value ranging from 7.12 - 15.37) and 14 HER2 negative (test value ranging from 1.05 - 6.92).

Conclusion: Application of Q-RT-PCR for HER2 represents a viable approach to resolve HER2 status in cases that fail classification by both FISH and IHC. Q-RT-PCR combines the precision and high sensitivity of real-time PCR with the morphological specificity of histological evaluation and ultimately allows definitive HER2 classification at the time of initial diagnosis. This knowledge of HER2 status at the time of diagnosis allows for comprehensive neoadjuvant treatment although, additional studies correlating response to anti-HER2 therapy and HER2 status by Q-RT-PCR are warranted.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P1-07-05.

Molecular pathology of breast cancer: the journey from traditional practice toward embracing the complexity of a molecular classification

CONTEXT

Adenocarcinoma of the breast is the most frequent cancer affecting women in both developed and developing regions of the world. From the moment of clinical presentation until the time of pathologic diagnosis, patients affected by this disease will face daunting questions related to prognosis and treatment options. While improvements in targeted therapies have led to increased patient survival, these same advances have created the imperative to accurately stratify patients to achieve maximum therapeutic efficacy while minimizing side effects. In this evolving era of personalized medicine, there is an ever-increasing need to overcome the limitations of traditional diagnostic practice.

OBJECTIVE

To summarize the molecular diagnostics traditionally used to guide prognostication and treatment of breast carcinomas, to highlight published data on the molecular classification of these tumors, and to showcase molecular assays that will supplement traditional methods of categorizing the disease.

DATA SOURCES

A review of the literature covering the molecular diagnostics of breast carcinomas with a focus on the gene expression and array studies used to characterize the molecular signatures of the disease. Special emphasis is placed on summarizing evolving technologies useful in the diagnosis and characterization of breast carcinoma.

CONCLUSIONS

Available and emerging molecular resources will allow pathologists to provide superior diagnostic, prognostic, and predictive information about individual breast carcinomas. These advances should translate into earlier identification and tailored therapy and should ultimately improve outcome for patients affected by this disease.

Inhibition of transcription factor activity by nuclear compartment-associated Bcl-2

Using a reporter gene assay in PC12, HEK293, HeLa, and NIH-3T3 cells, we show that the anti-apoptotic protein Bcl-2 significantly inhibits transcriptional activation of various transcription factors, including NF kappa B, AP1, CRE, and NFAT. A Bcl-2 mutant lacking its BH4 domain (Delta BH4) also inhibited transcription, whereas a Bcl-2 mutant lacking its transmembrane domain (Delta TM) was ineffective. Furthermore, Bcl-2 chimeric proteins containing transmembrane domains from the mitochondrial protein monoamine oxidase B (MaoB) or the endoplasmic reticulum protein cytochrome b(5) showed no effect on transcription factor activity. Subcellular localization studies showed that under conditions of transient transfection, the active Bcl-2 forms (wild type and Delta BH4) were predominantly found in the nuclear fraction, whereas the non-active forms (Delta TM, MaoB, and cytochrome b(5)) were in the non-nuclear fraction. Additionally, stably expressed Bcl-2 loses its ability to inhibit transcriptional activation and localizes predominantly to the non-nuclear fraction. Expression of FKBP38 (a chaperone that shuttles Bcl-2 to the mitochondria) removes co-expressed Bcl-2 from the nuclear fraction and reverses its effect on transcription factor activity. Finally, using an inducible gene expression system, we show that nuclear compartment-associated Bcl-2 prevents entry of NF kappa B subunits to the nucleus without affecting NF kappa B release from its cytosolic inhibitory sub-unit I kappa B alpha. These results suggest that (a) Bcl-2 suppresses transcriptional activity of multiple transcription factors; (b) Bcl-2 does not interfere with NF kappa B activation but prevents entrance of its active subunits to the nucleus; (c) membrane anchoring is required for this function of Bcl-2; and (d) association of Bcl-2 with the nuclear compartment is also necessary. We speculate that nuclear compartment-associated Bcl-2 may affect nuclear trafficking of multiple factors necessary for transcriptional activity.

A transcript map of the chromosome 19q-arm glioma tumor suppressor region

Allelic loss of the chromosome 19q arm is a frequent event in human diffuse gliomas, suggesting that it contains a tumor suppressor gene. Recent deletion mapping studies have broadly implicated a 1.6-Mb interval between D19S241E and D19S596, with a limited subset of tumors, suggesting that the region may be as narrow as 150 kb. Focusing on this smaller interval, we have used cDNA selection, exon amplification, and genomic sequencing to identify three novel transcripts (EHD2, GLTSCR1, and GLTSCR2) and to map two known genes (SEPW1 and CRX). A partial transcript map of 19 transcripts and two EST markers has been constructed for the 1.6-Mb interval D19S241E-D19S596. Ten of these transcripts, including the 5 mapped to the 150-kb deletion interval, have been examined for alterations in a panel of gliomas with allelic loss of 19q. Tumor-specific alterations have not been identified in the transcripts examined thus far. Collectively, these data should facilitate subsequent efforts to identify and characterize the remaining transcripts in the 1.6-Mb interval.

The human glia maturation factor-gamma gene: genomic structure and mutation analysis in gliomas with chromosome 19q loss

Human glia maturation factor-gamma (hGMF-gamma) is a recently identified gene that may be involved in glial differentiation, neural regeneration, and inhibition of tumor cell proliferation. The gene maps to the long arm of chromosome 19 at band q13.2, a region that is frequently deleted in human malignant gliomas and is thus suspected to harbor a glioma tumor suppressor gene. Given the putative role of hGMF-gamma in cell differentiation and proliferation and its localization to chromosome 19q13, this gene is an interesting candidate for the chromosome 19q glioma tumor suppressor gene. To evaluate this possibility, we determined the genomic structure of human hGMF-gamma and performed mutation screening in a series of 41 gliomas with and without allelic loss of chromosome 19q. Mutations were not detected, which suggests that hGMF-gamma is not the chromosome 19q glioma suppressor gene. However, the elucidation of the genomic structure of hGMF-gamma may prove useful in future investigations of hGMF-gamma in the normal adult and developing human nervous system.