Acinar cell cystadenoma of the pancreas: report of three cases and literature review.

INTRODUCTION: Acinar cell cystadenoma (ACC) of the pancreas was first described as a distinct pancreatic cystic neoplasm in 2002. METHODS: We have encountered three cases of ACC at our institution in addition to the 15 cases reported to date in the world literature. The gender distribution in the total cohort of patients with ACC slightly favored females (61 % female), and the median age was 49.5 years. RESULTS: Almost half (53 %) of the cases were identified incidentally, while the remainder presented with abdominal pain. The median tumor diameter was 5 cm in size, and no patients have had documented disease recurrence or progression, even in the setting of an incomplete resection. CONCLUSION: These findings suggest a relatively indolent biology, and that complete resections are curative. As we will show, surgical resection is warranted to treat symptoms and prevent local extension or malignant transformation.

The canonical NF-kappaB pathway governs mammary tumorigenesis in transgenic mice and tumor stem cell expansion.

The role of mammary epithelial cell (MEC) NF-κB in tumor progression in vivo is unknown, as murine NF-κB components and kinases either are required for murine survival or interfere with normal mammary gland development. As NF-κB inhibitors block both tumor-associated macrophages (TAM) and MEC NF-κB, the importance of MEC NF-κB to tumor progression in vivo remained to be determined. Herein, an MEC-targeted inducible transgenic inhibitor of NF-κB (IκBαSR) was developed in ErbB2 mammary oncomice. Inducible suppression of NF-κB in the adult mammary epithelium delayed the onset and number of new tumors. Within similar sized breast tumors, TAM and tumor neoangiogenesis was reduced. Coculture experiments demonstrated MEC NF-κB enhanced TAM recruitment. Genome-wide expression and proteomic analysis showed that IκBαSR inhibited tumor stem cell pathways. IκBαSR inhibited breast tumor stem cell markers in transgenic tumors, reduced stem cell expansion in vitro, and repressed expression of Nanog and Sox2 in vivo and in vitro. MEC NF-κB contributes to mammary tumorigenesis. As we show that NF-κB contributes to expansion of breast tumor stem cells and heterotypic signals that enhance TAM and vasculogenesis, these processes may contribute to NF-κB-dependent mammary tumorigenesis.

Alternative cyclin D1 splice forms differentially regulate the DNA damage response.

The DNA damage response (DDR) activates downstream pathways including cell cycle checkpoints. The cyclin D1 gene is overexpressed or amplified in many human cancers and is required for gastrointestinal, breast, and skin tumors in murine models. A common polymorphism in the human cyclin D1 gene is alternatively spliced, resulting in cyclin D1a and D1b proteins that differ in their carboxyl terminus. Cyclin D1 overexpression enhances DNA damage-induced apoptosis. The role of cyclin D1 and the alternative splice form in regulating the DDR is not well understood. Herein cyclin D1a overexpression enhanced the DDR as characterized by induction of γH2AX phosphorylation, the assembly of DNA repair foci, specific recruitment of DNA repair factors to chromatin, and G(2)-M arrest. Cyclin D1 deletion in fibroblasts or small interfering RNA-mediated reduction of endogenous cyclin D1 in colon cancer cells reduced the 5-fluorouracil-mediated DDR. Mechanistic studies showed that cyclin D1a, like DNA repair factors, elicited the DDR when stably associated with chromatin.

p21CIP1 attenuates Ras- and c-Myc-dependent breast tumor epithelial mesenchymal transition and cancer stem cell-like gene expression in vivo.

p21(CIP1/WAF1) is a downstream effector of tumor suppressors and functions as a cyclin-dependent kinase inhibitor to block cellular proliferation. Breast tumors may derive from self-renewing tumor-initiating cells (BT-ICs), which contribute to tumor progression, recurrence, and therapy resistance. The role of p21(CIP1) in regulating features of tumor stem cells in vivo is unknown. Herein, deletion of p21(CIP1), which enhanced the rate of tumorigenesis induced by mammary-targeted Ha-Ras or c-Myc, enhanced gene expression profiles and immunohistochemical features of epithelial mesenchymal transition (EMT) and putative cancer stem cells in vivo. Silencing of p21(CIP1) enhanced, and expression of p21(CIP1) repressed, features of EMT in transformed immortal human MEC lines. p21(CIP1) attenuated oncogene-induced BT-IC and mammosphere formation. Thus, the in vitro cell culture assays reflect the changes observed in vivo in transgenic mice. These findings establish a link between the loss of p21(CIP1) and the acquisition of breast cancer EMT and stem cell properties in vivo.

The cell fate determination factor DACH1 is expressed in estrogen receptor-alpha-positive breast cancer and represses estrogen receptor-alpha signaling.

The Dachshund (dac) gene, initially cloned as a dominant inhibitor of the Drosophila hyperactive EGFR mutant ellipse, encodes a key component of the cell fate determination pathway involved in Drosophila eye development. Analysis of more than 2,200 breast cancer samples showed improved survival by some 40 months in patients whose tumors expressed DACH1. Herein, DACH1 and estrogen receptor-alpha (ERalpha) expressions were inversely correlated in human breast cancer. DACH1 bound and inhibited ERalpha function. Nuclear DACH1 expression inhibited estradiol (E(2))-induced DNA synthesis and cellular proliferation. DACH1 bound ERalpha in immunoprecipitation-Western blotting, associated with ERalpha in chromatin immunoprecipitation, and inhibited ERalpha transcriptional activity, requiring a conserved DS domain. Proteomic analysis identified proline, glutamic acid, and leucine rich protein 1 (PELP1) as a DACH1-binding protein. The DACH1 COOH terminus was required for binding to PELP1. DACH1 inhibited induction of ERalpha signaling. E(2) recruited ERalpha and disengaged corepressors from DACH1 at an endogenous ER response element, allowing PELP1 to serve as an ERalpha coactivator. DACH1 expression, which is lost in poor prognosis human breast cancer, functions as an endogenous inhibitor of ERalpha function.

Single-cell transcription site activation predicts chemotherapy response in human colorectal tumors.

Candidate gene and pathway approaches, and unbiased gene expression profiling, have identified marker signatures predictive of tumor phenotypes, such as drug sensitivity and invasive or metastatic potential. However, application of such information to evaluation of tumors in the clinic is limited by cell heterogeneity in the tumor. We have developed a novel method of fluorescence in situ hybridization (FISH) that can detect transcriptional activation of individual genes at their site in single cells in the interphase nucleus. A major obstacle in the treatment of colorectal cancer is relative insensitivity to the chemotherapeutic agent 5-Fluorouracil (5-FU). Here, we have developed a sensitive approach to predict relative sensitivity of colorectal cancer cells to 5-FU, using FISH with probes targeted to nascent mRNAs to measure the number of individual cells with active transcription sites for a panel of candidate genes. These results reveal that the transcriptional status of four key genes, thymidylate synthase (TYMS), MORF-related gene X (MRGX), Bcl2-antagonist/killer (BAK), and ATPase, Cu(2+) transporting beta polypeptide (ATP7B), can accurately predict response to 5-FU. As proof of principle, we show that this transcriptional profile is predictive of response to 5-FU in a small number of patient colon tumor tissues. This approach provides a novel ability to identify and characterize unique minor cell populations in the tumor that may exhibit relative resistance to chemotherapy.

Inhibition of cyclin D1 gene transcription by Brg-1.

The evolutionarily conserved SWI-SNF chromatin remodeling complex regulates cellular proliferation. A catalytic subunit, BRG-1, is frequently down regulated, silenced or mutated in malignant cells, however, the mechanism by which BRG-1 may function as a tumor suppressor or block breast cancer cellular proliferation is not understood. The cyclin D1 gene is a collaborative oncogene overexpressed in greater than 50% of human breast cancers. Herein, BRG-1 inhibited DNA synthesis and cyclin D1 expression in human MCF-7 breast cancer epithelial cells. The cyclin D1 promoter AP-1 and CRE sites were required for repression by BRG-1 in promoter assays. BRG-1 deficient cells abolished and siRNA to BRG-1 reduced, formation of the BRG-1 chromatin complex. The endogenous cyclin D1 promoter AP-1 site bound BRG-1. Estradiol treatment of MCF-7 cells induced recruitment of BRG-1 to the endogenous hpS2 gene promoter. Estradiol, which induced cyclin D1 abundance, was associated with a reduction in recruitment of the co-repressors HP1alpha/HDAC1 to the endogenous cyclin D1 promoter AP-1/BRG-1 binding sites. These studies suggest the endogenous cyclin D1 promoter BRG-1 binding site functions as a molecular scaffold in the context of local chromatin upon which coactivators and corepressors are recruited to regulate cyclin D1.

Sirtuins, nuclear hormone receptor acetylation and transcriptional regulation.

Endocrine signaling via nuclear receptors (NRs) is known to play an important role in normal physiology as well as in human tumor progression. Hormones regulate gene expression by altering local chromatin structure and, thereby, accessibility of transcriptional co-regulators to DNA. Recently it has been shown that non-histone proteins involved in hormone signaling, such as nuclear receptors and NR co-activators, are regulated by acetylation, resulting in their altered transcriptional activity. NAD-dependent protein deacetylases, the sirtuins (Sir2-related enzymes), directly modify NRs. Because sirtuins have been shown to regulate tumor cellular growth, aging, metabolic signaling and endocrine hormone signaling, they might play a role in cancer progression. This review focuses on the role of acetylation and the sirtuins in nuclear hormone receptor signaling.

The functional significance of nuclear receptor acetylation.

The endocrine signaling governing nuclear receptor (NR) function has been known for several decades to play a crucial role in the onset and progression of several tumor types. Notably among these are the estrogen receptor (ER) in breast cancer and androgen receptor (AR) in prostate cancer. Other nuclear receptors may be involved in cancer progression including the peroxisome-proliferator activating receptor gamma (PPARgamma), which has been implicated in breast, thyroid, and colon cancers. These NR are phylogenetically conserved modular transcriptional regulators, which like histones, undergo post-translational modification by acetylation, phosphorylation and ubiquitination. Importantly, the transcriptional activity of the receptors is governed by the coactivator p300, the activity of which is thought to be rate-limiting in the activity of these receptors. Histone acetyltransferases (HATs) and histone deacetylases (HDACs), modify histones by adding or removing an acetyl group from the epsilon amino group of lysines within an evolutionarily conserved lysine motif. Histone acetylation results in changes in chromatin structure in response to specific signals. These enzymes can also directly catalyze the NRs themselves, thus modifying signals at the receptor level. The post-translational modification of NR which is regulated by hormones, alters the NR function toward a growth promoting receptor. The deacetylation of NR is mediated by TSA-sensitive and NAD-dependent deacetylases. The regulation of NR by NAD-dependent enzymes provides a direct link between intracellular metabolism and hormone signaling.