Christa L. Whitney-Miller

Kras(G12D) and p53 mutation cause primary intrahepatic cholangiocarcinoma.

Intrahepatic cholangiocarcinoma (IHCC) is a primary cancer of the liver with an increasing incidence and poor prognosis. Preclinical studies of the etiology and treatment of this disease are hampered by the relatively small number of available IHCC cell lines or genetically faithful animal models. Here we report the development of a genetically engineered mouse model of IHCC that incorporates two of the most common mutations in human IHCC, activating mutations of Kras (Kras(G12D)) and deletion of p53. Tissue-specific activation of Kras(G12D) alone resulted in the development of invasive IHCC with low penetrance and long latency. Latency was shortened by combining Kras(G12D) activation with heterozygous or homozygous deletion of p53 (mean survival of 56 weeks vs. 19 weeks, respectively), which also resulted in widespread local and distant metastasis. Serial analysis showed that the murine models closely recapitulated the multistage histopathologic progression of the human disease, including the development of stroma-rich tumors and the premalignant biliary lesions, intraductal papillary biliary neoplasms (IPBN), and Von Meyenburg complexes (VMC; also known as biliary hamartomas). These findings establish a new genetically and histopathologically faithful model of IHCC and lend experimental support to the hypothesis that IPBN and VMC are precursors to invasive cancers.

Eosinophilic Esophagitis A Retrospective Review of Esophageal Biopsy Specimens From 1992 to 2004 at an Adult Academic Medical Center

Eosinophilic esophagitis (EE), initially described in children, is now recognized in adults. The prevalence of EE in adults is largely unknown. Our goals were to determine the prevalence of EE in an adult population undergoing esophagogastroduodenoscopy with biopsy as originally reported and on retrospective review, the rate at which EE was present before this diagnosis was readily appreciated, and whether the prevalence of EE has changed over time. We reviewed esophageal biopsy specimens from 1992 to 2004. If there were more than 15 eosinophils per high-power field and confirmatory clinical information was available, EE was diagnosed. The initial (prereview) prevalence was 1.3%; prevalence on retrospective review was 1.7%. Prevalence was higher in later years (3.8%) compared with early years (0.3%). The demographics of our patients with EE are generally similar to what has been reported. Our results suggest the prevalence of EE is increasing and that pathologists provide accurate diagnoses in the face of changing criteria and significance.

MicroRNA-494 is a master epigenetic regulator of multiple invasion-suppressor microRNAs by targeting ten eleven translocation 1 in invasive human hepatocellular carcinoma tumors.

Vascular invasion provides a direct route for tumor metastasis. The degree to which microRNA (miRNA) expression plays a role in tumor vascular invasion is unclear. Here, we report that miR‐494 is up‐regulated in human hepatocellular carcinoma (HCC) tumors with vascular invasion and can promote HCC cell invasiveness by gene inactivation of multiple invasion‐suppressor miRNAs. Our results show that ten eleven translocation (TET) methylcytosine dioxygenase, predominantly TET1 in HCC cells, is a direct target of miR‐494. The reduced 5′‐hydroxymethylcytosine levels observed in the proximal cytosine‐phosphate‐guanine (CpG) regions of multiple invasion‐suppressor miRNA genes are strongly associated with their transcriptional repression upon miR‐494 overexpression, whereas enforced DNA demethylation can abolish the repression. Furthermore, TET1 knockdown shows a similar effect as miR‐494 overexpression. Conversely, miR‐494 inhibition or enforced TET1 expression is able to restore invasion‐suppressor miRNAs and inhibit miR‐494‐mediated HCC cell invasion. Conclusions: miR‐494 can trigger gene silencing of multiple invasion‐suppressor miRNAs by inhibiting genomic DNA demethylation by direct targeting of TET1, thereby leading to tumor vascular invasion. (Hepatology 2015;62:466–480

Plac8 Links Oncogenic Mutations to Regulation of Autophagy and Is Critical to Pancreatic Cancer Progression

Mutations in p53 and RAS potently cooperate in oncogenic transformation, and correspondingly, these genetic alterations frequently coexist in pancreatic ductal adenocarcinoma (PDA) and other human cancers. Previously, we identified a set of genes synergistically activated by combined RAS and p53 mutations as frequent downstream mediators of tumorigenesis. Here, we show that the synergistically activated gene Plac8 is critical for pancreatic cancer growth. Silencing of Plac8 in cell lines suppresses tumor formation by blocking autophagy, a process essential for maintaining metabolic homeostasis in PDA, and genetic inactivation in an engineered mouse model inhibits PDA progression. We show that Plac8 is a critical regulator of the autophagic machinery, localizing to the lysosomal compartment and facilitating lysosome-autophagosome fusion. Plac8 thus provides a mechanistic link between primary oncogenic mutations and the induction of autophagy, a central mechanism of metabolic reprogramming, during PDA progression.

HER2 testing in gastric and gastroesophageal junction cancers: a new therapeutic target and diagnostic challenge.

Adenocarcinomas of the stomach and gastroesophageal junction represent a major cause of cancer morbidity and mortality world wide. Complete surgical resection is the mainstay of treatment for nonmetastatic disease; however, many patients are not diagnosed until their disease is either locally advanced or metastatic and therefore unresectable. Clearly, there is an unmet clinical need for new therapeutic strategies, treatment options, and novel therapeutic targets. In a recent trial (Trastuzumab for GAstric cancer), patients assigned to the trastuzumab treatment protocol showed an improved overall survival over those not receiving treatment. Trastuzumab has recently been approved for treatment of advanced gastric and gastroesophageal junction cancers. Pathologists and diagnostic laboratories must be prepared for this new category of specimens requiring human epidermal growth factor receptor 2 testing, and have an awareness of the interpretive differences between breast and gastric cancers.

The evolving role of HER2 evaluation for diagnosis and clinical decision making for breast and gastric adenocarcinoma

Abstract Clinical laboratory testing for human epidermal growth factor receptor-2 (HER2) in patients with newly diagnosed breast and gastric cancer is critically important for therapeutic decisions about adjuvant treatment. The HER2 pathway is a major molecular driver of disease progression in a subset of these solid tumors and the results of HER2 testing determine which patients are likely to respond to an expanding variety of therapies that target this important biologic pathway. Given the significant clinical impact of these test results on patient management and adjuvant treatment decisions, standardization of the assay for HER2 and assured reliability of these results are critical. We review highlights of the clinical rationale that underlies HER2 testing for both breast and gastric carcinomas, and describe some of the challenges associated with ensuring accurate test results.

HER2 testing in gastric and esophageal adenocarcinoma: new diagnostic challenges arising from new therapeutic options

Abstract Adenocarcinomas of the esophagus and stomach constitute a substantial number of cancer cases worldwide. Most patients in the United States are diagnosed at an advanced or metastatic stage and, therefore, the prognoses have been poor. New treatments are needed to augment standard surgical and medical management. Recent studies have shown that a subset of esophageal and gastric adenocarcinomas overexpress the HER2 protein, similar to the overexpression seen in breast cancer. Because trastuzumab, a monoclonal antibody to the HER2 receptor, has been used with success in primary and HER2 positive metastatic breast cancers, the phase III ToGA trial was designed to assess the impact of trastuzumab in patients with HER2 positive gastric cancers. They have reported an increase in overall survival time for patients treated with chemotherapy and trastuzumab compared to those treated with chemotherapy alone. They have reported an increase in overall survival time for patients treated with chemotherapy and trastuzumab compared to those treated with chemotherapy alone. This means that accurate HER2 testing in gastric and esophageal carcinomas is necessary. While the breast cancer scoring system can be used to determine HER2 status in most cases, modifications are necessary to accommodate the heterogeneity and incomplete membrane staining that are observed more frequently in gastric cancers. An understanding of the scoring modifications is required for proper stratification of gastric cancer patients for treatment.

Immunohistochemistry as a surrogate for molecular subtyping of gastric adenocarcinoma

The Cancer Genome Atlas Research Network recently classified gastric adenocarcinoma into 4 molecular subtypes: Epstein-Barr virus-positive tumors, microsatellite-unstable tumors, tumors with chromosomal instability, and genomically stable tumors. We theorized that immunohistochemistry might be useful in similar categorization and that that HER2 expression might relate to subtype. We stained 104 gastric adenocarcinomas for MLH1, p53, and EBER in situ hybridization. We grouped them based on staining pattern and compared the groups. Cases were categorized as follows: group 1 (EBER positive), 7 cases (7%); group 2 (MLH1 deficient), 17 cases (16%); group 3 (aberrant p53 staining, EBER negative, retained MLH1), 40 cases (38%); group 4 (unremarkable staining), 40 cases (38%). This distribution was comparable to that found by the Research Network after accounting for the TP53 mutation rate in the chromosomal instability group. Group 1 patients had significantly longer follow-up times (median, 70 months versus 13 months for other groups; P = .0324). No group 2 cases overexpressed HER2. In group 3, 3 of 40 cases were HER2 immunohistochemistry positive, but 7 of 27 were HER2 positive by fluorescence in situ hybridization. Staining offers an efficient, reasonably accurate alternative for molecular subtyping of gastric adenocarcinoma, although some cases with chromosomal instability cannot be identified. These findings have potential prognostic and therapeutic implications.

Tissue pattern recognition error rates and tumor heterogeneity in gastric cancer.

The anatomic pathology discipline is slowly moving toward a digital workflow, where pathologists will evaluate whole-slide images on a computer monitor rather than glass slides through a microscope. One of the driving factors in this workflow is computer-assisted scoring, which depends on appropriate selection of regions of interest. With advances in tissue pattern recognition techniques, a more precise region of the tissue can be evaluated, no longer bound by the pathologist’s patience in manually outlining target tissue areas. Pathologists use entire tissues from which to determine a score in a region of interest when making manual immunohistochemistry assessments. Tissue pattern recognition theoretically offers this same advantage; however, error rates exist in any tissue pattern recognition program, and these error rates contribute to errors in the overall score. To provide a real-world example of tissue pattern recognition, 11 HER2-stained upper gastrointestinal malignancies with high heterogeneity were evaluated. HER2 scoring of gastric cancer was chosen due to its increasing importance in gastrointestinal disease. A method is introduced for quantifying the error rates of tissue pattern recognition. The trade-off between fully sampling tumor with a given tissue pattern recognition error rate versus randomly sampling a limited number of fields of view with higher target accuracy was modeled with a Monte-Carlo simulation. Under most scenarios, stereological methods of sampling-limited fields of view outperformed whole-slide tissue pattern recognition approaches for accurate immunohistochemistry analysis. The importance of educating pathologists in the use of statistical sampling is discussed, along with the emerging role of hybrid whole-tissue imaging and stereological approaches.

College of American Pathologists Guidelines for Reporting HER2 Test Results in Gastric Cancer.

To the Editor.—I disagree with Dr Sarewitz when he states that ‘‘in the future, most community pathologists will need to practice as subspecialists, and my kind of career path [as a general pathologist] will become obsolete.’’ After almost 40 years of private pathology practice, I see a bright future for pathology that rests in the hands of well-trained, boardcertified anatomic and clinical pathologists. The practice of future pathologists will be based not on subspecialization, but on the same skill set that marks today’s successful general pathologist. This skill set includes current competence, the ability to effectively communicate with colleagues, and (to paraphrase the film character Dirty Harry) a knowledge of their limitations. In our southern California group practice, more than 95% of our cases (breast, gastrointestinal, hematopathology, genitourinary, gynecology, etc) are signed out without the need of a subspecialist. In our metropolitan area, as in more remote practice areas, subspecialty consultation is easily obtained by US mail, messenger, or overnight delivery. Sarewitz states that in the future ‘‘there will be no reason for anyone to look at a brain frozen section except for a network’s neuropathologists.’’ In our practice, neurosurgeons operate late into the evening, and a pathologist is often requested for frozen section. I wonder who in Dr Sarewitz’s neuropathology network will come into the hospital to prepare and interpret a frozen section when requested by the neurosurgeon at 1 o’clock in the morning. I suspect none other than the general pathologist he sees as becoming obsolete. In my opinion, the network he envisions will simply not be necessary. I am optimistic about the future of pathology, competently practiced by board-certified anatomic and clinical pathologists rather than subspecialist pathologists.