All the Fabs kept their peptide-specific, MHC-restricted binding

All the Fabs kept their peptide-specific, MHC-restricted binding to the MOG-35-55 loaded empty RTL302-5D (Fig. 3B), excluding any binding dependence to non-native sequences of RTL1000. Additionally, we tested Fab binding to RTL1000 in different buffer conditions and found the Fabs to be conformationally sensitive, losing their ability to react with denatured RTL1000 (Supporting Information Fig. 1). Taken together, these data indicate selective Fab binding to the α1β1 DR2–MOG-35-55 native sequence of the folded RTL1000. We next tested the ability of the anti-RTL1000 Fabs to Olaparib bind the native full-length four-domain form of MHC-II complexes as expressed on APCs. L-cell DR*1501 transfectants

(L466.1 cells) were loaded with MOG-35-55 or control peptide. The loaded cells were incubated with the purified Fabs following anti-Fab-FITC incubation. As shown in Fig. 4A, no specific binding of Fabs was observed for MOG-35-55 loaded cells. MOG-35-55 and control-peptide loaded cells produced the same fluorescence

intensity as background. MHC expression on the APC surface was confirmed by anti-DR mAb (L243). A portion of the loaded cells that were used for the FACS analysis was incubated with the H2-1 T-cell hybridoma specific for the DR2–MOG-35-55 complex. Following 72 h incubation, cell supernatants were transferred to IL-2-dependent CTLL cells for detection of IL-2 levels secreted from the H2-1 hybridoma (Fig. 4B). H2-1 cells were activated U0126 in vitro only by the MOG-35-55 pulsed cells, secreting eightfold higher levels of IL-2 compared to non-pulsed or control peptide-pulsed APCs. Peptide-specific H2-1 activation confirmed a successful loading of MOG-35-55 peptide to the native MHC on the APCs used for the FACS analysis. Despite the presence of a biologically active determinant in the form of DR2–MOG-35-55

molecules presented by the APCs, no staining of such a complex was obtained by any of our anti RTL1000 Fabs. Considering the high affinity of the selected Fabs and the permissive conditions used for this experiment, we conclude that the Fabs do not bind the native DR2–MOG-35-55 complex presented by APCs. Further support for this finding came from blocking experiments which tested the Fabs ability to inhibit peptide-specific activation of the H2-1 hybridoma by DR2 Phosphoprotein phosphatase APCs pulsed with MOG-35-55 peptide (Fig. 4C). None of our selected Fabs were able to block this peptide-specific, MHC-restricted activation, as compared to a control TCRL Fab (D2) specific for RTL2010 (DR4–GAD-555-567) that also failed to block H2-1 activation. In contrast, complete blocking was achieved by the control anti-MHC-II mAb (TU39). The failure of the Fabs to interfere with MHC presentation to TCR implies an inability to bind native four domain DR2–MOG-35-55 complexes. This was indeed the case, as demonstrated by ELISA (Fig. 4D).

It is theoretically possible that the differences in the prevalen

It is theoretically possible that the differences in the prevalence of nonneutral CDR-H3s observed in the mature, recirculating B-cell pool reflect the changes in the complement of VH in C57BL/6 B cells when compared to BALB/c B cells. However, in previous studies of BALB/c mice, we have shown that changes in the global repertoire of CDR-H3 due to changes in DH content had no effect on VH utilization [17, 19, 21]. Thus, this possibility seemed less likely in C57BL/6 selleck products mice.

One of the first, critical somatic, clonal selective steps in repertoire development depends on the interaction between the H chain and the surrogate light chain λ5 and VpreB [22, 23]. Successful passage through this checkpoint permits Ulixertinib early pre-B fraction C cells to clonally expand and then transition to the late pre-B-cell fraction D stage at which light chain rearrangement occurs. Most of the selective influences that we had observed in developing BALB/c B lineage cells during this transition were also apparent in developing C57BL/6 B lineage cells. This included a decline in the use of VH81X, a decrease in the use of DH RF2 with a compensatory increase in the use of RF1, and a stabilization of average length and average charge

[8]. The latter two values in particular were indistinguishable between BALB/c fraction D and C57BL/6 fraction D (Fig. 4), suggesting that both mouse strains share similar preference for mechanistic regulation at the step where the interaction between the nascent heavy chain and the surrogate light chain components determine the efficiency almost of pre-BCR formation. For reasons unknown, BALB/c mice carrying the μMT mutation are leaky and can produce some B cells while C57BL/6 mice with

the same mutation are not leaky and do not produce B cells suggesting a different timing in the B-cell generation process [24]. Thus it is possible that differences in the timing of Dμ protein or pre-B-cell receptor expression between the two strains could have a downstream effect on repertoire development. A second selective step is the testing of the reactivity of the nascent IgM in fraction E. Failure at this step can lead to receptor editing, anergy, or cell death, reducing the likelihood of entry or survival of cells bearing “disfavored” IgM in the fraction F pool. Nussensweig et  al. have clearly demonstrated that this step selects against potentially pathogenic self-reactivity [25]. CDR-H3 sequences obtained from C57BL/6 fraction E cells showed a significant difference in the average hydrophobicity compared to BALB/c fraction E cells suggesting a difference in the intensity or consequences of self-antigen recognition at that stage between the two strains (Fig. 4B).

Nevertheless, this fine-tuning of NF-κB activation by β2 integrin

Nevertheless, this fine-tuning of NF-κB activation by β2 integrins contributed to dramatic differences in the ability of macrophages to respond to TLRs and induce NF-κB-dependent gene expression. Importantly, we noted that the affected genes encompassed both “primary response” (Tnf, Cxcl1, Cxcl2) and “secondary response” (Il12B, Il6) genes that encode for inflammatory cytokines, chemokines, and anti-apoptotic functions Sotrastaurin [38]. We also observed a direct effect

of β2 integrin deletion on enhancing p65/RelA binding to the Il12b (IL-12 p40) promoter downstream of LPS stimulation. However, it should be noted that fine-tuning of the NF-κB pathway by β2 integrins did not control expression of all “NF-κB-dependent” genes tested. Peculiar omissions from this list include A20 and iNOS, which were both expressed similarly between WT and Itgb2−/−

macrophages, suggesting that other pathways may be influenced by β2 integrin signals to control transcription of these genes. One such pathway is p38 MAPK signaling. Itgb2−/− macrophages demonstrated a reduced ability to phosphorylate, and therefore activate, p38 following LPS treatment, consistent with the fact that selleck chemicals β2 integrin outside-in signals are known to directly activate the MAPK pathway [14]. In addition to its well-regarded proinflammatory activities [39], activation of p38 and its subordinate protein kinases MSK1 and MSK2 has been implicated in dampening inflammation through several mechanisms. For example, p38 activity limits Th1 responses

to Leishmania by destabilizing IL-12 p40, though not TNF, mRNA stability [32]. p38 and MSK1/2-derived signals have also been shown to negatively regulate TLR responses by inhibiting inflammatory cytokine transcription directly or by promoting IL-10 synthesis through activation of CREB and Atf-1 transcription factors [30-32]. In addition to IL-10, p38-directed A20 and ABIN-3 production has previously been linked to TLR suppression by β2 integrins [20]. However, Itgb2−/− macrophage TLR hypersensitivity could not be attributed to deficiencies in A20, ABIN-3, Hes-1 or to changes in IL-10 production or signaling, arguing against a role for these proteins in β2 integrin-medited TLR suppression. Interestingly, Itgb2−/− macrophages presented with higher TLR-induced Niclosamide levels of some of these inhibitors than WT cells, likely owing to enhanced NF-κB activation. The differences between our results and those of Wang et al. [20] may be due to our use of plastic petri dishes to induce β2 integrin signals instead of plate-bound fibrinogen, which itself is known to bind to additional receptors [26-29]. Indeed, fibrinogen’s ability to dampen TLR activity in macrophages may be at least partially β2 integrin-independent as we found that inflammatory cytokine secretion was suppressed in Itgb2−/− macrophages similar to WT cells after plating onto fibrinogen-coated plates (data not shown).

5b) These data suggest that demethylation of this CpG island of

5b). These data suggest that demethylation of this CpG island of the Foxp3 promoter region correlates with Foxp3 expression. The methylation status of this region was evaluated in Foxp3− T cells that were activated for 72 hr in the presence of TGF-β alone, simvastatin alone, and the combination of TGF-β/simvastatin (Fig. 5c). After 72 hr, 48% and 42% of the CpGs of dimethylsulphoxide-treated or simvastatin-treated cells were methylated, respectively. However, this region in TGF-β-treated cells was less methylated (26%) than in dimethylsulphoxide-treated

or simvastatin-treated cells and the lowest level of methylation (16%) was observed in the cells treated with simvastatin/TGF-β. Seventy-two hours after activation, the extent of demethylation correlated well with the level of Foxp3 expression AZD2281 in vitro detected by FACS analysis (bottom boxes in Fig. 5c). These results suggest that the synergistic action of simvastatin on TGF-β-mediated induction of Foxp3 may be mediated by co-operative control of methylation of the Foxp3 promoter. To directly examine the effects of simvastatin on TGF-β-mediated signal transduction, we measured phosphorylation of Smad3. Significant phosphorylation of

Smad3 was observed 24 hr after activation of cells cultured in the presence of Ixazomib research buy TGF-β, but not simvastatin alone, and the levels of Smad3 phosphorylation were not modulated when the cultures were stimulated with both TGF-β and simvastatin (Fig. 6a). In addition, the total amount of Smad4 was comparable in all treatment groups. The lack of an effect of others simvastatin on Smad3 phosphorylation is consistent with its late time of action and raised the possibility that simvastatin might block steps in the negative-feedback regulation of TGF-β signalling. Smad6 and Smad7 are the major inhibitory Smad proteins in the negative feedback regulation

of the TGF-β signalling pathway. In contrast to Smad3 phosphorylation, we could not detect Smad7 by Western blot analysis 24 hr after T-cell activation and only low levels of Smad6 were observed. The levels of Smad6/7 increased after 48 hr and were maximal at 72 hr after activation (Fig. 6b). Importantly, when combined with TGF-β, simvastatin markedly inhibited the induction of Smad6 at 48 and 72 hr, and completely blocked Smad7 induction at both 48 and 72 hr. Simvastatin alone also decreased levels of Smad6 and completely blocked Smad7 expression at 72 hr. As TGF-β has been reported to play an important role in Foxp3+ Treg homeostasis,16 we also examined the expression of Smad6/7 in nTregs that were activated under conditions similar to those used in our iTreg induction cultures. Foxp3− and Foxp3+ CD4+ T cells were FACS-sorted from Foxp3gfp mice and activated with anti-CD3/CD28 and IL-2 in the absence or presence of TGF-β for 72 hr (Fig. 6c).

The dose of MSC administered to the mice was approximately 1–2 × 

The dose of MSC administered to the mice was approximately 1–2 × 106 Flk-1+ MSCs per mouse; compared to 108 or more splenocytes in each mouse, the stimulatory effect of Flk-1+ MSCs might play a dominant role on B cells in CIA animals.

Consistently, MSC-treated mice showed a mild increase in serum IgG compared to untreated CIA mice. Alternatively, the enhancement of splenocyte proliferation and IgG secretion in Flk-1+ MSC-treated mice might be caused by the specific in vivo environment of CIA, rather than a dose-dependent effect of Flk-1+ MSCs observed in in vitro culture. It is known that in vitro suppression in a mixed lymphocyte selleck chemical reaction (MLR) does not always correlate with in vivo immune modulation. To address this question, we

should increase the dose given to mice and examine the dose-dependency in vivo. However, we failed to increase the dose of MSC infusion to 1–2 × 107 because of pulmonary embolism and the subsequent death of the animals. The mechanism of the differential regulation of B cell proliferation by MSC in vitro is still unknown. Rasmusson et al. have reported previously that similar differential regulation of human B cells by MSCs might be associated with the intensity of stimulation [23]. The dose effect of MSC and the dose effect of stimulation might share some common mechanisms. IL-6 is a cytokine that enhances see more B cell function. The co-existence of increased production of

IL-6 (Fig. 4) and decreased proliferation of B cells (Fig. 5), while MSCs were co-cultured with splenocytes at ratio of 1:10, indicates that two independent pathways co-exist – one promotes B cells, and the other suppresses B cells. The subtle balance between them may explain the differential regulation of B cell proliferation by MSCs in our and other studies [23]. Flk-1+ MSCs exacerbated CIA only in the day 21 Protein kinase N1 infusion group and not in the day 0 group. The difference in the in vivo physiological environment of the animal between days 0 and 21 might account for this issue. The onset of arthritis begins after the second injection of CII on day 21. Therefore, the physiological condition of the animal on day 21 is closer to that of the animal suffering from arthritis, while the physiological condition of the animal on day 0 is closer to that of the healthy animals. The results of day 0 mice indicated that Flk-1+ MSCs did not have a preventive effect on CIA, and the results of day 21 showed the aggravation risks of treating CIA with Flk-1+ MSCs. In conclusion, we propose that elevated IL-6, by enhancing Th17 and plasma cells, is responsible for the aggravation of CIA after day 21 Flk-1+ MSC treatment (Fig. 6). In Phase II clinical trials of Flk-1+ MSCs, special attention should be paid to patients with rheumatoid arthritis.

Recognition of flagellin by NLRC4 is likely indirect and mediated

Recognition of flagellin by NLRC4 is likely indirect and mediated through host cellular factors, which trigger inflammasome activation since there is no evidence to date for a direct interaction between NLRC4 and flagellin. NLRC4 DAPT can sense additional molecules besides flagellin as certain aflagellated bacteria including S. flexneri14 and Mycobacterium tuberculosis21 activate caspase-1 via NLRC4. The NLR protein Naip5 is also critical for the sensing

of a conserved C-terminal portion of flagellin from L. pneumophila and for NLRC4-dependent caspase-1 activation 22. Remarkably, Naip5 is not required for caspase-1 activation triggers by S. typhimurium or P. aeruginosa infection 22. The mechanism by which Naip5 regulates the NLRC4 inflammasome activated by L. pneumophila remains

unclear 23. Because caspase-1 is critical for restricting the replication of L. pneumophila in the host cytosol, these studies suggest that both Naip5 and NLRC4 control the susceptibility to L. pneumophila through the sensing of flagellin and caspase-1 activation. Alternatively, Naip5 may have additional NLRC4-independent roles EPZ-6438 cost that are important in restricting the growth of L. pneumophila in macrophages. Recent studies suggest that caspase-7 which is activated by the NLRC4 inflammasome is an important factor in restricting L. pneumophila replication, although the mechanism involved remains elusive PD184352 (CI-1040) 24. While the NLRC4 inflammasome

is activated primarily by cytosolic flagellin, a plethora of microbial and non-microbial stimuli have been reported to activate caspase-1 via NLRP3. These include multiple TLR agonists and the Nod2 agonist, MDP 25, 26. In addition, large particles including urate crystals, silica, asbestos, β-amyloid and aluminum hydroxide activate the NLRP3 inflammasome in phagocytes pre-stimulated with microbial ligands such as LPS 6. Unlike TLR ligands, these particulate and crystalline molecules can activate the inflammasome in the absence of extracellular ATP 6. Although the critical cellular events remain poorly understood, disruption of the lysosomal membrane and/or production of ROS 27 have been suggested to be important for particulate matter-induced NLRP3 activation 28. The ability of multiple pathogen-associated molecular patterns to activate the NLRP3 inflammasome is puzzling because most of the molecules including TLR ligands are structurally unrelated. Recent findings suggest that most or all TLR agonists as well as MDP do not activate the NLRP3 inflammasome directly. Instead, they prime the inflammasome via NF-κB to promote caspase-1 activation 29, 30, which is consistent with previous results 31. Consistently, TNF-α and IL-1 are as effective as TLR agonists in promoting caspase-1 activation in response to ATP or silica 29.

6E) Accordingly, the expression of the death factor Nur77 was si

6E). Accordingly, the expression of the death factor Nur77 was significantly lower in Nlrp3−/− DCs (Fig. 6F). In support of these data, we observed significant increases in expression

of the pro-survival genes Xiap and Birc3 in Nlrp3−/− cells compared with WT DCs (Fig. 6F). Taken together, these data indicate that the NLRP3 inflammasome plays an important role in the DDR after oxidative and genotoxic stress, and that the p53 pathway is involved in NLRP3-mediated pyroptosis. Oxidative stress is now emerging as a common feature of immune responses to a variety of different insults. ROS generation was proposed as crucial step for activation of the NLRP3 inflammasome [14]. The majority of NLRP3 activators, including MSU, provoke a significant but transient Ku-0059436 ic50 increase

in ROS, pivotal for caspase-1-mediated release of IL-1β. Monocytes from patients with cryopyrinopathies associated with NLRP3 mutations display an altered redox state, which results in sustained IL-1β secretion, suggesting that redox signaling is important for NLRP3 activation Luminespib molecular weight [15]. Transient or permanent imbalance between the excess formation of ROS and limited antioxidant defenses can damage DNA, leading to activation of the DDR pathway. We found that disruption of NLRP3 inflammasome mediated signaling markedly reduced double-strand breaks and DNA oxidation (measured as γ-H2AX and 8-oxoG, respectively) by ROS-inducing stimuli (MSU and rotenone). Similar to Nlrp3−/− DCs, H2AX phosphorylation was significantly decreased in casp-1−/− DCs when compared with WT DCs at later time points. These results highlight that the NLRP3 inflammasome, and not NLRP3 alone, seems to be directly involved in promoting the DDR. However, a role for an alternative inflammasome complex in driving cellular responses to DNA damage cannot be excluded. Several observations indicate that the diverse DDR activation in WT compared to Nlrp3−/− cells can be explained by differential compensatory mechanisms elicited by oxidative stress, rather than early

events responsible for induction of DNA damage. Both ROS production and DNA damage are similar at early time points in WT and Nlrp3−/− or casp-1−/− cells, whereas the repair elements Ogg1 and NBS1 are significantly more induced at later Isotretinoin time in cells that lack NLRP3 signaling. However, the exact link between NLRP3 activation and oxidative repair remains unclear. It was proposed that increased ROS levels cause the detachment of thioredoxin-interacting protein from thioredoxin, a critical intracellular antioxidant, and its binding to NLRP3 during high glucose mediated caspase-1 activation in murine pancreatic B cells [10]. However, this remains controversial since caspase-1 activation and IL-1β secretion are similar in WT and Txnip−/− macrophages in response to islet amyloid polypeptide, MSU, or ATP [16].

When atrial rates are slow in the presence of complete AVB, which

When atrial rates are slow in the presence of complete AVB, which can occur when there is coexistent sinus node disease, distinction between complete and second-degree AVB may be difficult. Repeated assessments or longer periods of assessment at faster sweep speeds permit the diagnosis of complete AVB (Fig. 1). Conflicting data exist regarding the true incidence of 1° AVB [32–34] and the efficacy of mechanical A–V interval in predicting later AVB. In a recent study by Bergman et al. [32], of 92 antibody-positive pregnancies with prospective midtrimester evaluation of the mechanical A–V interval, 12 (13%) neonates had

1° AVB that spontaneously resolved within the first month, including 2 with higher grade AVB documented prenatally. Foetal mechanical A–V interval was prolonged (>95th percentile) in all but 1 affected Talazoparib neonate with a sensitivity of 91.7% and negative predictive value of 98.4%. However, the positive predictive value of mechanical interval (>95th percentile) for 1° AVB after birth was 50% with measurement from simultaneous

left ventricular inflow–outflow recordings and 59% for superior vena cava-aortic recordings. In this series, 62% of foetuses with prolonged mechanical Endocrinology antagonist A–V interval had no AV conduction abnormality after birth. In a study comparing foetal ECG with mechanical A–V interval, Gardiner et al. documented the sensitivity

and specificity of mechanical A–V prolongation, for predicting later foetal and neonatal AVB to be 44% and 88% respectively, when MTMR9 compared to 67% and 96% respectively for foetal ECG [35]. Their observation of prolonged foetal PR interval in a small number of foetuses without AVB after birth provides evidence that 1° AVB in utero occurs transiently in some affected pregnancies, but the discrepancy between foetal ECG and mechanical A–V interval measures suggests that other technical and physiological factors may influence the mechanical A–V interval. Finally, from several studies, it is clear that progression from prolonged A–V interval or 1° AVB to more severe AVB is not so common before or after birth [32, 34, 35]. Despite these observations, serial Doppler echocardiographic measurement of AV time intervals is a useful method for surveillance of at-risk pregnancies. What remains unclear at this time is the most optimal gestational age to initiate surveillance and the frequency of foetal echocardiographic surveillance for AVB and other cardiac complications of maternal autoantibodies. Furthermore, it is not possible to provide foetal echo surveillance for all affected pregnancies, especially if the incidence of anti-Ro and anti-La antibodies among pregnant women is 2–3% and <5% of these women will have an affected foetus.

In this study of propranolol therapy, Child-Pugh class C, hyponat

In this study of propranolol therapy, Child-Pugh class C, hyponatremia, and renal impairment were found to be independent variables of mortality in patients with cirrhosis with refractory ascites. As a result, the authors suggest that propranolol should be contraindicated in BMS-354825 cost these patients. Although the authors did not report the cardiac status of the patients, we would like to discuss their findings in this regard, upon the findings of two recent articles.2, 3 Krag et al.2 evaluated 24 patients with cirrhosis with a cardiac index (CI) above or below 1.5 L/minute/m2, and they found that patients with low CI showed significantly poorer

survival than those with a higher CI. In addition, hyponatremia and renal impairment, which are independent variables of mortality in the study report by Serste et al., were found to be associated with lower CI.2 Krag et al. stated that a cardio-renal relation in cirrhosis is most likely the result of chronic circulatory stress combined with more acute events, such as bacterial translocation and systemic inflammatory response, which trigger a systemic response. This may lead to progression of a systolic failure with a decrease in CI, starting a vicious circle in which check details the decreased CI leads to accentuated arterial underfilling, decreased arterial pressure,

and renal perfusion, resulting in deterioration of the renal function, which further enhances cardiac and renal deterioration. Recently, Sharma et al.3 investigated the effects of propranolol on normotensive and hypertensive patients with cirrhosis; they showed

that CI significantly decreased after propranolol therapy in both groups. Based on these findings, we think that lowering effects of propranolol on CI and consecutively, development of hyponatremia and renal impairment, may explain the possible mechanism of deleterious effects of propranolol on survival in these Terminal deoxynucleotidyl transferase patients. Finally, the common usage of beta-blockers for the prevention of variceal bleeding may change in the near future, at least in patients with severe cirrhosis, and band ligation and/or therapies that improve CI may be considered as emerging treatment options to improve survival. Cumali Efe M.D.*, Tugrul Purnak M.D.†, Ersan Ozaslan M.D.†, * Departments of Internal Medicine, Numune Research and Education Hospital, Ankara, Turkey, † Gastroenterology, Numune Research and Education Hospital, Ankara, Turkey. “
“A 50-year-old woman was admitted to hospital with hematemesis and hypotension. She had previously been well. Her hemoglobin was 7.9 g/dL (79 g/l) and she had a mild elevation of alanine aminotransferase (102 u/l) and alkaline phosphatase (187 u/l). At upper gastrointestinal endoscopy, oozing of blood from superficial gastric ulcers was treated with injections of adrenaline.

Dysplasia is a marker of malignant potential and a determinant of

Dysplasia is a marker of malignant potential and a determinant of surveillance colonoscopy intervals, and therefore, provides a meaningful division for the categorization of serrated polyps. Dysplasia can occur in at least two forms in serrated polyps: conventional cytological dysplasia similar to that which occurs in conventional adenomas, and serrated dysplasia. Cytological dysplasia is seen in a subset of SSA/SSP,

suggesting a more aggressive phenotype, and such lesions are referred to as SSA-D/SSP-D. The term “mixed polyp” was previously used for these lesions, but is no longer recommended. Although TSA might also display conventional cytological dysplasia, they are mostly characterized by serrated dysplasia.2 Serrated dysplasia does not demonstrate markers of proliferation, such as increased mitosis or staining with Ki67. Rather, the cells appear senescent, Pembrolizumab research buy with abundant eosinophilic cytoplasm. When conventional dysplasia is also seen in a TSA, an increased likelihood of malignant conversion is assumed. A unique property of TSA is ectopic crypt formation. This offers a more definitive feature for its recognition, as well as an explanation selleck chemicals for the exophytic growth of TSA compared to SSA/SSP, where this feature is not observed.

It has also been suggested that this loss of anchorage of the crypt base in TSA is a reflection of molecular differences between TSA and SSA/SSP, which reflects the genetic program of mucosal development underlying TSA.2 The process whereby a serrated polyp undergoes malignant transformation is widely referred to as the “serrated pathway”. Within this field of study, the “canonical serrated pathway” is perhaps the best known, and has been proposed to explain STK38 the progression of an SSA/SSP through SSA-D/SSP-D to a colorectal cancer.4 SSA/SSP have high rates of somatic BRAF mutation, and widespread DNA methylation known as CpG island methylator phenotype. Cancers arising from SSA also show these molecular features,

and comprise an estimated 15–20% of the total colorectal cancer burden.5 Both SSA and SSP, and the cancers they give rise to, are concentrated in the proximal colon. Less is known about the pathway to colorectal cancer associated with TSA, and as yet, this pathway has no definitive steps. The differentiation of SSA and TSA at the morphological level has been facilitated by studies of their fine structure. Molecularly, TSA do not demonstrate unique features, and can harbor somatic mutations in BRAF or KRAS or neither of these. They are not highly methylated and are concentrated in the distal colon. The senescent appearance of a TSA highlights a possible defect in the rate of apoptosis in these lesions, but to date, there is no single gene mutation has been assigned to this particular pathway, and further genetic/epigenetic molecular markers would be of value. Mutations in mitochondrial DNA (mtDNA) have been associated with defects in apoptosis.