Tumour infiltrating lymphocytes and apoptosis are independent features in colorectal cancer stratified according to microsatellite instability status

Background-The presence of high level DNA microsatellite instability (MSI-H) in colorectal cancer is associated with an improved prognosis, as is the presence of tumour infiltrating lymphocytes (TILs). It is not clear if TILs contribute directly to the survival advantage associated with MSI-H cancers through activation of an antitumour immune response. Aims-To correlate TIL and apoptosis rates in colorectal cancer stratified by MSI status. Methods-The distribution of TILs was characterised and quantified in a selected series of 102 sporadic colorectal cancers classified according to levels of MSI as 32 MSI-H, 30 MSI-low (MSI-L), and 40 microsatellite stable (MSS). Archival blocks were immunostained using the T cell markers CD3 and CD8, and the B cell marker CD20. Apoptosis of malignant epithelial cells was quantified by immunohistochemistry with the M30 CytoDEATH antibody. Results-Positive staining with anti-CD3 and negative staining with anti-CD20 identified virtually all TILs as T cells. The majority of CD3(+) TILs (>75%) also stained with anti-CDS. TILs were most abundant in MSI-H colorectal cancers in which 23/32 (72%) scored as TIL positive. Only 5/40 (12.5%) MSS tumours and 9/30 (30%) MSI-L cancers were TIL positive (p

Stimulation of protein kinase C-dependent and -independent signaling pathways by bistratene A in intestinal epithelial cells

The marine toxin bistratene A (BisA) potently induces cytostasis and differentiation in a variety of systems. Evidence that BisA is a selective activator of protein kinase C (PKC) delta implicates PKC delta signaling in the negative growth-regulatory effects of this agent. The current study further investigates the signaling pathways activated by BisA by comparing its effects with those of the PKC agonist phorbol 12-myristate 13-acetate (PMA) in the IEC-18 intestinal crypt cell line. Both BisA and PMA induced cell cycle arrest in these cells, albeit with different kinetics. While BisA produced sustained cell cycle arrest in G(o)/G(1) and G(2)/M, the effects of PMA were transient and involved mainly a G(o)/G(1), blockade. BisA also produced apoptosis in a proportion of the population, an effect not seen with PMA. Both agents induced membrane translocation/activation of PKC, with BisA translocating only PKC delta and PMA translocating PKC alpha, delta, and epsilon in these cells. Notably, while depletion of PKC alpha, delta, and epsilon abrogated the cell cycle-specific effects of PMA in IEC-18 cells, the absence of these PKC isozymes failed to inhibit BisA-induced G(o)/G(1), and G(2)/M arrest or apoptosis. The cell cycle inhibitory and apoptotic effects of BisA, therefore, appear to be PKC-independent in IEG-18 cells. On the other hand, BisA and PMA both promoted PKC-dependent activation of Erk 1 and 2 in this system. Thus, intestinal epithelial cells respond to BisA through activation of at least two signaling pathways: a PKC delta -dependent pathway, which leads to activation of mitogen-activated protein kinase and possibly cytostasis in the appropriate context, and a PKC-independent pathway, which induces both cell cycle arrest in G(o)/G(1) and G(2)/M and apoptosis through as yet unknown mechanisms. (C) 2001 Elsevier Science Inc. All rights reserved.

Accumulation of manganese in Neisseria gonorrhoeae correlates with resistance to oxidative killing by superoxide anion and is independent of superoxide dismutase activity

As a facultative aerobe with a high iron requirement and a highly active aerobic respiratory chain, Neisseria gonorrhoeae requires defence systems to respond to toxic oxygen species such as superoxide. It has been shown that supplementation of media with 100 muM Mn(II) considerably enhanced the resistance of this bacterium to oxidative killing by superoxide. This protection was not associated with the superoxide dismutase enzymes of N. gonorrhoeae. In contrast to previous studies, which suggested that some strains of N. gonorrhoeae might not contain a superoxide dismutase, we identified a sodB gene by genome analysis and confirmed its presence in all strains examined by Southern blotting, but found no evidence for sodA or sodC. A sodB mutant showed very similar susceptibility to superoxide killing to that of wild-type cells, indicating that the Fe-dependent SOD B did not have a major role in resistance to oxidative killing under the conditions tested. The absence of a sodA gene indicated that the Mn-dependent protection against oxidative killing was independent of Mn-dependent SOD A. As a sodB mutant also showed Mn-dependent resistance to oxidative killing, then it is concluded that this resistance is independent of superoxide dismutase enzymes. Resistance to oxidative killing was correlated with accumulation of Mn(II) by the bacterium. We hypothesize that this bacterium uses Mn(II) as a chemical quenching agent in a similar way to the already established process in Lactobacillus plantarum. A search for putative Mn(II) uptake systems identified an ABC cassette-type system (MntABC) with a periplasmic-binding protein (MntC). An mntC mutant was shown to have lowered accumulation of Mn(II) and was also highly susceptible to oxidative killing, even in the presence of added Mn(II). Taken together, these data show that N. gonorrhoeae possesses a Mn(II) uptake system that is critical for resistance to oxidative stress.

Television and cultural studies: Unfinished business

This introductory article argues that the current state of debate on television within cultural studies is marked by considerable areas of theoretical and political uncertainty. The spread of deregulatory and privatizing public policies in relation to television, and the disarticulation of television from the idea of the national community and from the role of the citizen, have posed new problems for theorizing the relation between television and its audiences. In this article I survey a number of key areas of debate: the relation between television, the nation and the state; television and the citizen/consumer, television content and performance, and the likely future(s) of television.