A super-enhancer-regulated RNA-binding protein cascade drives pancreatic cancer.

Pancreatic ductal adenocarcinoma (PDAC) is a lethal malignancy in need of new therapeutic options. Using unbiased analyses of super-enhancers (SEs) as sentinels of core genes involved in cell-specific function, here we uncover a druggable SE-mediated RNA-binding protein (RBP) cascade that supports PDAC growth through enhanced mRNA translation. This cascade is driven by a SE associated with the RBP heterogeneous nuclear ribonucleoprotein F, which stabilizes protein arginine methyltransferase 1 (PRMT1) to, in turn, control the translational mediator ubiquitin-associated protein 2-like. All three of these genes and the regulatory SE are essential for PDAC growth and coordinately regulated by the Myc oncogene. In line with this, modulation of the RBP network by PRMT1 inhibition reveals a unique vulnerability in Myc-high PDAC patient organoids and markedly reduces tumor growth in male mice. Our study highlights a functional link between epigenetic regulation and mRNA translation and identifies components that comprise unexpected therapeutic targets for PDAC.

KRAS testing and its importance in colorectal cancer.

Cetuximab and panitumumab are monoclonal antibodies used in the treatment of metastatic colorectal cancer (mCRC) by selectively targeting the epidermal growth factor receptor (EGFR) axis. Studies have shown that mutations in codons 12/13 of exon 2 of the KRAS gene render these therapies ineffective. As a result, the National Comprehensive Cancer Network and American Society of Clinical Oncology recommend KRAS mutation testing in mCRC. Appropriate testing depends on the coordinated efforts of the entire treatment team, including the pathologist, who selects the tumor sample and testing platform as well as interprets and reports results. In addition to describing rationale and methodologies for KRAS mutation testing, the authors also summarize their algorithmic approach and elaborate the potential role of newer molecular biomarkers to predict anti-EGFR resistance in wild-type KRAS tumors.

A five-marker panel in a multiplex PCR accurately detects microsatellite instability-high colorectal tumors without control DNA.

Microsatellite instability (MSI) testing is used to screen for Lynch syndrome. The current technique for MSI determination requires DNA from normal and neoplastic tissue and is expensive and laborious. Five quasi-monomorphic markers (NR-21, BAT-25, MONO-27, NR-24, and BAT-26) are included in the Promega MSI analysis kit. With the working hypothesis that this 5-marker panel can accurately determine the MSI status of colorectal tumors without using paired control DNA, we evaluated 478 colorectal tumors and divided them into a test group (N=172, colorectal adenocarcinomas) and a validation group (N=306 including 179 colorectal adenocarcinomas and 127 adenomas). The quasi-monomorphic variation range of each marker was generated from the test group (172 normal samples) and used as a reference value in the subsequent interpretation of MSI status in the test and validation groups. Considering the MSI result using a 5-marker panel with paired control DNA as the gold standard, we identified 136 microsatellite stable (MSS) and 36 microsatellite instability-high (MSI-H) colorectal tumors in the test group and 259 MSS and 47 MSI-H colorectal tumors in the validation group. Using the quasi-monomorphic variation range of each marker rather than paired normal DNA, the 5-marker panel identified all MSI-H colorectal tumors in the test and validation groups, when MSI-H was defined as ≥2 unstable markers. Our study demonstrates that the 5-marker panel within a multiplex polymerase chain reaction of the Promega MSI analysis kit accurately identifies all MSI-H and 95.2% MSS colorectal tumors without using paired normal DNA.

Transformation of chronic lymphocytic leukemia/small lymphocytic lymphoma to interdigitating dendritic cell sarcoma: evidence for transdifferentiation of the lymphoma clone.

Interdigitating dendritic cell sarcoma (IDCS) is a rare tumor derived from interdigitating dendritic cells. Three cases of IDCS associated with chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) have been described, but no clonal relationship between the 2 neoplasms was demonstrated. We present a detailed case analysis of a CLL/SLL with metachronous IDCS and demonstrate that these 2 neoplasms are clonally related. The IDCS and CLL cells had trisomy 12 and identical monoclonal immunoglobulin heavy chain gene rearrangements. Analysis of transcription factors with a role in myeloid differentiation demonstrated PU.1 up-regulation and C/EBPalpha down-regulation in IDCS compared with CLL. High-density array comparative genomic hybridization also identified gains in part of chromosome 16q in IDCS. Our study demonstrates for the first time clonal transformation of CLL/SLL into IDCS. This phenomenon may be triggered by alterations in lineage-determining transcription programs, which result in transdifferentiation, coupled with additional oncogenic stimuli caused by chromosomal imbalances.

Placental mesenchymal dysplasia.

CONTEXT: Placental mesenchymal dysplasia is characterized by placentomegaly and may be mistaken for molar pregnancy both clinically and macroscopically because of the presence of "grapelike vesicles." It may be associated with a completely normal fetus, a fetus with growth restriction, or a fetus with features of Beckwith-Wiedemann syndrome. OBJECTIVE: To review the etiology, molecular pathology, gross and microscopic features, clinical presentation, complications, and differential diagnosis of placental mesenchymal dysplasia. DATA SOURCES: The PubMed and the Medline databases were systematically searched for articles between 1970 and 2006. The following keywords were used: placental mesenchymal dysplasia, mesenchymal hyperplasia, molar pregnancy, pseudomolar pregnancy, Beckwith-Wiedemann syndrome, and placentomegaly. Relevant references from review articles were also searched. CONCLUSIONS: Placental mesenchymal dysplasia should be considered in the differential diagnosis when the ultrasonographic findings show a cystic placenta. Close attention should be paid to fetal morphology for early recognition of fetal complications and to prevent unnecessary termination of pregnancy in cases associated with a normal fetus.