Sigmoid volvulus: is it a possible complication after stapled transanal rectal resection (STARR)?

We report a case of sigmoid volvulus post-stapled transanal rectal resection (STARR) for obstructed defecation. The patient, a 68-yearold woman with chronic constipation and dolichosigma, two days post-STARR presented severe abdominal pain. CT revealed sigmoid ischemia. The patient underwent resection of the sigmoid colon with end colostomy (Hartmann's procedure). Can STARR procedure produce a serious complication as sigmoid volvulus in patient with dolichosigma and obstructed defecation syndrome?

Essential, non-redundant roles of B-Raf and Raf-1 in Ras-driven skin tumorigenesis.

Ras-driven tumorigenesis is assumed to depend on Raf for ERK activation and proliferation; yet, an in vivo requirement for Raf as MEK/ERK activator in this setting has not been demonstrated to date. Here, we show that epidermis-restricted B-Raf ablation restrains the onset and stops the progression of established Ras-driven tumors by limiting MEK/ERK activation and proliferation. Concomitant elimination of B-Raf and Raf-1 enforces the abrupt regression of established tumors owing to the decrease in ERK activation and proliferation caused by B-Raf ablation combined with the ERK-independent increase in Rho-dependent kinase (Rok) signaling and differentiation triggered by Raf-1 inactivation. Thus, B-Raf and Raf-1 have non-redundant functions in Ras-driven tumorigenesis. Of note, Raf kinase inhibitors achieve impressive results in melanomas harboring oncogenic BRAF, but are ineffective against Ras-driven tumors; moreover, therapy-related skin tumors driven by a paradox ERK activation as well as primary and acquired resistance have been reported. Our results suggest that therapies targeting both Raf kinase-dependent and -independent pathways may be effective against a broader range of malignancies and reduce the risks of adverse effects and/or resistance.

Raf kinases in cancer-roles and therapeutic opportunities.

Raf are conserved, ubiquitous serine/protein kinases discovered as the cellular elements hijacked by transforming retroviruses. The three mammalian RAF proteins (A, B and CRAF) can be activated by the human oncogene RAS, downstream from which they exert both kinase-dependent and kinase-independent, tumor-promoting functions. The kinase-dependent functions are mediated chiefly by the MEK/ERK pathway, whose activation is associated with proliferation in a broad range of human tumors. Almost 10 years ago, activating BRAF mutations were discovered in a subset of human tumors, and in the past year treatment with small-molecule RAF inhibitors has yielded unprecedented response rates in melanoma patients. Thus, Raf qualifies as an excellent molecular target for anticancer therapy. This review focuses on the role of BRAF and CRAF in different aspects of carcinogenesis, on the success of molecular therapies targeting Raf and the challenges they present.

Ras and Raf pathways in epidermis development and carcinogenesis.

The epidermis is the outermost layer of the body and protects it from environmental insults. This crucial function is sustained by a continuous process of self-renewal involving the carefully balanced proliferation and differentiation of progenitor cells constantly replacing the mature cells at the surface of the epidermis. Genetic changes in the signalling pathways controlling keratinocyte proliferation and differentiation disrupt this balance and lead to pathological changes including carcinogenesis. This review discusses the role of Ras, an oncogene critically involved in the development of skin neoplasia, and its downstream effector Raf in epidermal homeostasis and tumourigenesis. In particular, we will focus on the recently established role of Raf-1 as the decisive element that, by restraining keratinocyte differentiation, allows the development and maintenance of Ras-driven tumours.

B-Raf is required for ERK activation and tumor progression in a mouse model of pancreatic beta-cell carcinogenesis.

Activation of the Raf/MEK/ERK pathway, often by gain-of-function mutations of RAS or RAF, is observed in many human cancers. The extracellular signal-regulated kinase (ERK) pathway is required for the proliferation of cancer cell lines harboring activating BRAF or, to a lesser extent, activating RAS mutations. It is still unclear, however, whether the pathway is required in vivo for tumor development, particularly in tumors in which B-Raf is not mutationally activated. During embryonic development, B-Raf is essential for angiogenesis in the placenta. To address the question of whether B-Raf contributed to tumor angiogenesis in vivo we conditionally ablated B-Raf in a model of pancreatic islet carcinoma driven by the functional inactivation of tumor suppressors (RIP1Tag2), which critically depends on angiogenesis for growth. We find that B-Raf is dispensable for the proliferation of tumor cells in culture, but necessary for ERK activation and for the expression of angiogenic factors by tumor cells in vivo and in vitro. In vivo, these defects result in the formation of hollow tumors with decreased vessel density and strongly reduced proliferation. The progression from adenoma to carcinoma is also significantly impaired. Thus, endogenous B-Raf contributes to the development of RIP1Tag2 tumors by supporting the stromal response and tumor progression.

Digital stereotactic biopsies for nonpalpable breast lesion.

BACKGROUND: Percutaneous biopsy (BP) is a valid alternative to open surgical biopsy. The aim of our study was to evaluate the results and diagnostic value of vacuum-assisted core biopsy (VACB; Mammotome) and advanced breast biopsy instrumentation (ABBI). METHODS: From June 1999 to December 2001, 360 BPs were performed: all patients had dubious mammography lesions not confirmed by ultrasonography. Indications were as follows 264 (73.3%) microcalcifications, 64 (17.8%) nodular opacities, and 32 (8.8%) parenchymal distortions. RESULTS: All BPs were performed with a digital stereotactic table with a vacuum suction aspiration system for VACB and a cutting cannula for ABBI. All BPs were correctly performed. Seventy-one (19.7%) lesions were malignant, whereas 258 (71.6%) were benign: 31 (8.6%) of the lesions removed with VACB were atypical ductal hyperplasia. CONCLUSIONS: BP is a valid method for the diagnosis of nonpalpable breast lesions. In our experience, VACB is the method of choice because it is easy to perform and has high adaptability.

A clinicopathological study of 152 surgically treated primary gastric lymphomas with survival analysis of 109 high grade tumours.

AIMS: To describe the clinicopathological features of a large number of surgically treated and followed up primary gastric lymphomas and thereby gain a better understanding of their biology, with particular reference to the prognostic factors of high grade tumours. METHODS: A retrospective study of 152 patients. RESULTS: High grade gastric lymphomas, both pure and with a residual low grade component, differed from low grade mucosa associated lymphoid tissue (MALT)-type lymphomas in that they were more frequently large, ulcerated, at an advanced stage, and highly proliferating. In addition, patients were older and had a worse outcome. The prognosis of high grade lymphomas was influenced by patient age, tumour stage, depth of infiltration in the gastric wall, and the invasion of adjacent organs. Adjuvant postsurgical treatment prolonged survival only in patients with advanced stage and deep neoplastic infiltration. CONCLUSIONS: There is a sharp distinction between low grade MALT-type lymphomas and tumours with a high grade component, justifying their different treatment approach. The postsurgical management of high grade lymphomas should be based on the accurate evaluation of the neoplastic extension.

Embryonic lethality and fetal liver apoptosis in mice lacking the c-raf-1 gene.

The Raf kinases play a key role in relaying signals elicited by mitogens or oncogenes. Here, we report that c-raf-1(-/-) embryos are growth retarded and die at midgestation with anomalies in the placenta and in the fetal liver. Although hepatoblast proliferation does not appear to be impaired, c-raf-1(-/-) fetal livers are hypocellular and contain numerous apoptotic cells. Similarly, the poor proliferation of Raf-1(-/-) fibroblasts and hematopoietic cells cultivated in vitro is due to an increase in the apoptotic index of these cultures rather than to a cell cycle defect. Furthermore, Raf-1- deficient fibroblasts are more sensitive than wild- type cells to specific apoptotic stimuli, such as actinomycin D or Fas activation, but not to tumor necrosis factor-alpha. MEK/ERK activation is normal in Raf-1-deficient cells and embryos, and is probably mediated by B-RAF. These results indicate that the essential function of Raf-1 is to counteract apoptosis rather than to promote proliferation, and that effectors distinct from the MEK/ERK cascade must mediate the anti-apoptotic function of Raf-1.

Protective role of Raf-1 in Salmonella-induced macrophage apoptosis.

Invasive Salmonella induces macrophage apoptosis via the activation of caspase-1 by the bacterial protein SipB. Here we show that infection of macrophages with Salmonella causes the activation and degradation of Raf-1, an important intermediate in macrophage proliferation and activation. Raf-1 degradation is SipB- and caspase-1-dependent, and is prevented by proteasome inhibitors. To study the functional significance of Raf-1 in this process, the c-raf-1 gene was inactivated by Cre-loxP-mediated recombination in vivo. Macrophages lacking c-raf-1 are hypersensitive towards pathogen-induced apoptosis. Surprisingly, activation of the antiapoptotic mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) and nuclear factor kappaB pathways is normal in Raf-1-deficient macrophages, and mitochondrial fragility is not increased. Instead, pathogen-mediated activation of caspase-1 is enhanced selectively, implying that Raf-1 antagonizes stimulus-induced caspase-1 activation and apoptosis.

Salmonella-induced caspase-2 activation in macrophages: a novel mechanism in pathogen-mediated apoptosis.

The enterobacterial pathogen Salmonella induces phagocyte apoptosis in vitro and in vivo. These bacteria use a specialized type III secretion system to export a virulence factor, SipB, which directly activates the host's apoptotic machinery by targeting caspase-1. Caspase-1 is not involved in most apoptotic processes but plays a major role in cytokine maturation. We show that caspase-1-deficient macrophages undergo apoptosis within 4-6 h of infection with invasive bacteria. This process requires SipB, implying that this protein can initiate the apoptotic machinery by regulating components distinct from caspase-1. Invasive Salmonella typhimurium targets caspase-2 simultaneously with, but independently of, caspase-1. Besides caspase-2, the caspase-1-independent pathway involves the activation of caspase-3, -6, and -8 and the release of cytochrome c from mitochondria, none of which occurs during caspase-1-dependent apoptosis. By using caspase-2 knockout macrophages and chemical inhibition, we establish a role for caspase-2 in both caspase-1-dependent and -independent apoptosis. Particularly, activation of caspase-1 during fast Salmonella-induced apoptosis partially relies on caspase-2. The ability of Salmonella to induce caspase-1-independent macrophage apoptosis may play a role in situations in which activation of this protease is either prevented or uncoupled from the induction of apoptosis.

The Raf-1 kinase associates with vimentin kinases and regulates the structure of vimentin filaments.

Using immobilized GST-Raf-1 as bait, we have isolated the intermediate filament protein vimentin as a Raf-1-associated protein. Vimentin coimmunoprecipitated and colocalized with Raf-1 in fibroblasts. Vimentin was not a Raf-1 substrate, but was phosphorylated by Raf-1-associated vimentin kinases. We provide evidence for at least two Raf-1-associated vimentin kinases and identified one as casein kinase 2. They are regulated by Raf-1, since the activation status of Raf-1 correlated with the phosphorylation of vimentin. Vimentin phosphorylation by Raf-1 preparations interfered with its polymerization in vitro. A subset of tryptic vimentin phosphopeptides induced by Raf-1 in vitro matched the vimentin phosphopeptides isolated from v-raf-transfected cells labeled with orthophosphoric acid, indicating that Raf-1 also induces vimentin phosphorylation in intact cells. In NIH 3T3 fibroblasts, the selective activation of an estrogen-regulated Raf-1 mutant induced a rearrangement and depolymerization of the reticular vimentin scaffold similar to the changes elicited by serum treatment. The rearrangement of the vimentin network occurred independently of the MEK/ERK pathway. These data identify a new branch point in Raf-1 signaling, which links Raf-1 to changes in the cytoskeletal architecture.

Lipopolysaccharide induces jun N-terminal kinase activation in macrophages by a novel Cdc42/Rac-independent pathway involving sequential activation of protein kinase C zeta and phosphatidylcholine-dependent phospholipase C.

The activation of kinases of the mitogen-activated protein kinase superfamily initiated by lipopolysaccharide (LPS) plays an important role in transducing inflammatory signals. The pathway leading to the induction of stress-activated protein kinases in macrophages stimulated with LPS was investigated. The activation of Jun N-terminal kinases (JNK) by LPS is herbimycin sensitive. Using specific inhibitors, it was shown that the pathway involves the activation of phosphoinositide 3-kinase (PI 3-K). However, in contrast to previous reports, the small GTPases Cdc42 and Rac are not required downstream of PI 3-K for JNK activation. Instead, the phosphoinositides produced by PI 3-K stimulate protein kinase C (PKC) zeta activation through PDK1. In turn, activation of this atypical PKC leads to the stimulation of phosphatidylcholine phospholipase C (PC-PLC) and acidic sphingomyelinase (ASMase). It is therefore proposed that PKCzeta regulates the PC-PLC/ASMase pathway, and it is hypothesized that the resultant ceramide accumulation mediates the activation of the SEK/JNK module by LPS.

Microvessel quantitation in intraductal and early invasive breast carcinomas.

OBJECTIVE: To study the angiogenic process in intraductal carcinoma of the breast, with and without a small focus of stromal infiltration, and to compare the microvessel density between the in situ phase and the early infiltration phases of breast cancer. STUDY DESIGN: Microvessel density (number of microvessels per square millimeter of neoplasia) was quantitatively evaluated on anti-factor VIII-immunostained histologic sections obtained from 10 ductal carcinomas in situ (DCIS) (category A), 22 DCIS with a small focus of stromal infiltration (category B), 10 microinvasive carcinomas (category C), 12 T1a carcinomas (category D) and 20 T1b carcinomas (category E). RESULTS: The five categories of lesion had different values for microvessel density (P = .0017). Category A had microvessel density lower than category B (P = .0005). Category B had microvessel density higher than categories C, D and E (P = .0028, .0133 and .0033, respectively). CONCLUSION: Microvessel density seems to be a feature related to each crucial step in the early phases of neoplastic progression.

Constitutive activation of the MAPK pathway mediates v-fes-induced mitogenesis in murine macrophages.

Fes is a nonreceptor tyrosine kinase expressed at the highest level in macrophages. We previously showed that the overexpression of c-fes in murine macrophages of the BAC-1.2F5 cell line renders these cells independent of macrophage colony-stimulating factor (MCSF) for survival and proliferation, although no direct relationship could be established between tyrosine-phosphorylated substrates of Fes- and MCSF receptor-dependent signaling and mitogenesis. In this study, we investigated whether the mitogen-activated protein kinase (MAPK) pathway is involved in the growth factor-independent growth of v-fes-overexpressing macrophages. We found a constitutively increased phosphorylation of extracellularly regulated kinase (ERK) in v-fes-overexpressing macrophages as compared with mock-infected cells. This finding was associated with activation of mitogen/extracellular signal-regulated kinase (MEK) and with constitutive localization of ERK in the nucleus. Treatment of v-fes-overexpressing cells with the MEK-specific inhibitor PD98059 markedly reduced cell growth, hyperphosphorylation, and nuclear localization of ERK, indicating that the MAPK pathway mediates the mitogenic effect of v-fes. (Blood. 2000;95:3959-3963)

Chromatin texture analysis of cortical adrenal gland adenomas, including incidentalomas, and adjacent normal-appearing cortical tissue.

OBJECTIVE: To describe, by morphometric and chromatin texture analysis, a series of adrenal gland lesions, including Cushing's and Conn's adenomas and incidentalomas. STUDY DESIGN: The material for the study consisted of five consecutive cases of incidentaloma, three cases of Conn's adenoma and three cases of Cushing's adenoma. Also included were five cases of adrenal carcinoma. Sections were stained according to the Feulgen procedure. Measurements were taken from the nodules and from two different zones, identified as outer and inner parts, of the normal-appearing adrenal cortex adjacent to the tumor. Data on approximately 50 nuclei were recorded for each of these three sites (tumor and outer and inner normal-appearing adrenal cortex). The nuclei were subjected to feature extraction and were analyzed by identification procedures--i.e., establishing nuclear and lesion signatures. RESULTS: The total optical density (OD) distributions of the nuclei from the normal-appearing adrenal cortex pointed to their diploid or near-diploid nature. In incidentalomas there was a very small increase in the number of nuclei, with increased total OD. In Conn's adenoma there was a noticeable but modest extension of the total OD distribution into the higher OD range. This trend continued for Cushing's adenoma. The pixel OD histograms for nuclei from normal-appearing tissue and from incidentalomas were hardly distinguishable. Starting with nuclei from Conn's adenoma, a shift toward lower pixel OD values began. The trend continued for nuclei from Cushing's adenoma and was very pronounced for nuclei from carcinoma. The nuclear signatures showed no appreciable difference between nuclei from normal-appearing cortex and from incidentaloma. Nuclei from Conn's adenoma were more similar to those from normal tissue in their signatures than nuclei from Cushing's adenoma. In fact, the nuclear signatures from Cushing's adenoma were almost identical to those of carcinoma. The lesion signatures for normal tissue, incidentaloma and Conn's adenoma confirmed the results seen in the nuclear signatures. There was a very modest increase in the number of nuclei with greater deviation from normal in incidentalomas, and the trend was more obvious in Conn's adenoma. However, in Cushing's adenoma there was a very substantial increase in the number of nuclei, with large deviations of their nuclear chromatin texture from normal. CONCLUSION: Computer-assisted analysis of nuclear characteristics proved useful in identifying and describing differences between groups of tumors arising in the adrenal cortex and highlighted the similarity between incidentalomas and adjacent normal-appearing cortex and between Cushing's adenoma and adrenal carcinoma.

Raf-1-associated protein phosphatase 2A as a positive regulator of kinase activation.

The Raf-1 kinase plays a key role in relaying proliferation signals elicited by mitogens or oncogenes. Raf-1 is regulated by complex and incompletely understood mechanisms including phosphorylation. A number of studies have indicated that phosphorylation of serines 259 and 621 can inhibit the Raf-1 kinase. We show that both serines are hypophosphorylated during early mitogenic stimulation and that hypophosphorylation correlates with peak Raf-1 activation. Concentrations of okadaic acid that selectively inhibit protein phosphatase 2A (PP2A) induce phosphorylation of these residues and prevent maximal activation of the Raf-1 kinase. This effect is mediated via phosphorylation of serine 259. The PP2A core heterodimer forms complexes with Raf-1 in vivo and in vitro. These data identify PP2A as a positive regulator of Raf-1 activation and are the first indication that PP2A may support the activation of an associated kinase.

Distinct mechanisms target stress and extracellular signal-activated kinase 1 and Jun N-terminal kinase during infection of macrophages with Salmonella.

The interaction between bacteria and macrophages is central to the outcome of Salmonella infections. Salmonella can escape killing by these phagocytes and survive and multiply within them, giving rise to chronic infections. Cytokines produced by infected macrophages are involved in the early gastrointestinal pathology of the infection as well as in the induction and maintenance of the immune response against the invaders. Jun N-terminal kinases (JNK) are activated by inflammatory stimuli and play a role in cytokine production. We have investigated the signaling routes leading to JNK activation in Salmonella-infected macrophages and have discovered that they differ radically from the mechanisms operating in epithelial cells. In particular, activation of the JNK kinase stress and extracellular-activated kinase 1 (SEK1) and of JNK in macrophages occurs independently of actin rearrangements and of the GTPases Cdc42 and Rac, essential mediators in other cells. Activation of JNK is effected by a novel pathway comprising tyrosine kinase(s), phosphoinositide 3-kinase and, likely, atypical protein kinase C zeta. SEK1 is stimulated by a distinct mechanism involving phosphatidylcholine-phospholipase C and acidic sphingomyelinase. Dominant-negative SEK1 can block JNK activation by LPS, but not by Salmonella. These data demonstrate that SEK1 and JNK are activated independently in Salmonella-infected macrophages and offer experimental support for the concept that incoming signals can direct the selective coupling of downstream pathways to elicit highly specific responses. Inhibitors of stress kinase pathways are receiving increasing attention as potential anti-inflammatory drugs. The precise reconstruction of stimulus-specific pathways will be instrumental in predicting/evaluating the effects of the inhibitors on a given pathological condition.

Ploidy, proliferative activity, p53 and bcl-2 expression in bronchopulmonary carcinoids: relationship with prognosis.

Bronchopulmonary well-differentiated neuroendocrine carcinoma (WDNEC) represents a more aggressive neoplasm than does typical carcinoid. Its biological behavior is variable and cannot be predicted on the basis of histopathological features. Nineteen typical carcinoids and 23 WDNECs were studied in order to obtain multiple parameters that should be used in the differential diagnosis between these two lesions and as prognostic markers of WDNEC. Flow-cytometry was performed on paraffin-embedded sections. Mutant p53 protein, the bcl-2 oncoprotein and the Ki-67 antigen were detected by immunohistochemical methods and evaluated quantitatively. WDNEC was more frequently aneuploid than typical carcinoid, had a higher percentage of Ki-67 positive nuclei and presented more frequently the mutant p53 protein. In WDNEC, the mutant p53 (p = 0.001), the bcl-2 oncoprotein (p = 0.002) and the high expression (> or = 16%) of Ki-67 (p = 0.0021) were associated with poor prognosis. The prognostic significance of mutant p53 and bcl-2 oncoprotein could be confirmed by Cox multiple regression survival analysis (p = 0.0005). It seems to be advisable to evaluate these features for the management of the patients affected by WDNEC.

Raf-1 and B-Raf proteins have similar regional distributions but differential subcellular localization in adult rat brain.

The Raf kinases play an important and specific role in the activation of extracellular signal-regulated kinases (ERK) cascade. Beside its role in the control of proliferation and differentiation, the ERK cascade has also been implicated in neuron-specific functions. In order to gain clues on the function of Raf kinases in the adult central nervous system (CNS), we performed a comparative analysis of the distribution and subcellular localization of the different Raf kinases in rat brain with antibodies specific for the different Raf kinases. We show that B-Raf and Raf-1 proteins are present in most brain areas, whereas A-Raf is not detected. Interestingly, the two Raf proteins have an approximately similar pattern of distribution with a rostro-caudal decreasing gradient of expression. These two kinases are colocalized in neurons but they are differentially located in subcellular compartments. Raf-1 is localized mainly in the cytosolic fraction around the nucleus, whereas B-Raf is widely distributed in the cell bodies and in the neuritic processes. In addition, we demonstrated that numerous B-Raf isoforms are present in the brain. These isoforms have a differential pattern of distribution, some of them being ubiquitously expressed whereas others are localized to specific brain areas. These isoforms also have a clear differential subcellular localization, specially in Triton-insoluble fractions, but also in synaptosomal, membrane and cytosolic compartments. Altogether these results suggest that each Raf protein could have a distinct signalling regulatory function in the brain with regard to its subcellular localization.

Growth phase-regulated induction of Salmonella-induced macrophage apoptosis correlates with transient expression of SPI-1 genes.

Invasive Salmonella has been reported to induce apoptosis in a fraction of infected macrophages within 2 to 14 h from the time of infection by a mechanism involving the type III secretion machinery encoded by the Salmonella pathogenicity island 1 (SPI-1). Here, we show that bacteria in the transition from logarithmic to stationary phase cause 90% of the macrophages to undergo phagocytosis-independent, caspase-mediated apoptosis within 30 to 60 min of infection. The ability of Salmonella to induce this rapid apoptosis was growth phase regulated and cell type restricted, with epithelial cells being resistant. Apoptosis induction was also abrogated by disruption of the hilA gene (encoding a regulator of SPI-1 genes) and by the expression of a constitutively active PhoPQ. hilA itself and a subset of SPI-1 genes were transiently expressed during aerobic growth in liquid medium. Interestingly, however, hilA was found to be required only for the expression of the prgH gene, while sipB, invA, and invF were expressed in a hilA-independent manner. The expression of SPI-1 genes and the secretion of invasion-associated proteins correlated temporally with the induction of apoptosis and are likely to represent its molecular basis. Thus, growth phase transition regulates the expression and secretion of virulence determinants and represents the most efficient environmental cue for apoptosis induction reported to date.