Regulation of the intestinal mucin MUC2 gene expression in vivo: evidence for the role of promoter methylation

In the present work we investigated the in vivo regulation of the mucin gene MUC2, which is overexpressed in all mucinous colorectal carcinomas. The inhibition of methylation by 5-azadeoxycytidine induces de novo expression of MUC2 in the colon carcinoma cell line COLO 205. The expression is retained in xenograft tissue and the cells give rise to MUC2-expressing tumours in nude mice. The strong expression of MUC2 in the normal human goblet cells and in the tissue of human mucinous colorectal carcinomas is associated with the average methylation of about 50% at every investigated CpG site of the MUC2 promoter. In contrast, MUC2 promoter in the non-expressing normal columnar cells and in the non-mucinous carcinoma tissue is methylated to nearly 100%. These data show that (i) low methylation of MUC2 promoter is associated with MUC2 expression in vivo and (ii) the pattern of MUC2 promoter methylation in the normal goblet or columnar cells most closely resembles that in mucinous or non-mucinous colorectal carcinomas, respectively. They indicate that MUC2 expression in vivo is regulated by promoter methylation and support the hypothesis that cells with goblet-like differentiation give rise to mucinous colonic carcinomas.

Hodgkin and reed-sternberg cells represent an expansion of a single clone originating from a germinal center B-cell with functional immunoglobulin gene rearrangements but defective immunoglobulin transcription

Single cell studies aimed at clarifying the nature and clonality of Hodgkin and Reed-Sternberg (HRS) cells of classical Hodgkin's disease (HD) have so far produced conflicting results. Using an improved single cell procedure, the HRS cells of 25 patients with nodular sclerosing HD lacking B- and T-cell antigens, with and without Epstein-Barr virus infection, were analyzed for the presence of immunoglobulin (Ig) gene rearrangements. One patient with HD developed follicular lymphoma 2 years later. Both lymphomas originated from a common precursor identified as a germinal center B cell. The data show that all but one of the investigated cases harbored rearranged Ig genes, which were clonal in all instances and carried a high load of somatic mutations. The Ig coding capacity was preserved in 18 of the 24 cases (75%) with rearrangements. However, expression of Ig messenger RNA was not detectable in the HRS cells with the exception of Ig kappa light chain expression in some tumor cells of 1 case. The lack of Ig gene transcription in HRS cells was confirmed by analyzing the HD cell lines L428 and KM-H2 in transient transfection experiments. An Ig promoter/enhancer reporter construct showed virtually no activity in these cells compared to 5 control B-cell lines. We conclude that (1) classical HD is a B-cell lymphoma in most instances, (2) HRS cells are clonal without any exception, (3) they are derived from germinal center B-cells that (4) mostly lack crippling mutations but (5) have consistently lost their Ig gene transcription ability, due to functional defects in the Ig gene regulatory elements. (Blood. 2000;95:1443-1450)

A new UHV angle encoder for high-resolution synchrotron radiation monochromators

The high precision of 0.1 arcsec required for the positioning of optical elements in new two-axes monochromators at the undulator beamlines at BESSY II has led to the development of UHV-compatible high-precision angle encoders. Mounted directly on the rotation axes, they provide substantial advantages over measuring systems connected outside the vacuum vessel. Making use of a fast closed-loop control system, an accuracy of 0.1 arcsec at a resolution of less than 0.01 arcsec has been experimentally verified.

Hodgkin's disease with monoclonal and polyclonal populations of Reed-Sternberg cells

BACKGROUND

There is strong evidence that Reed-Sternberg cells have a lymphoid phenotype, but clonally rearranged genes for B-cell and T-cell antigen receptors have not been demonstrable in tumor tissue from most patients with Hodgkin's disease. To elucidate this issue, we assayed single Reed-Sternberg cells from 12 patients with classic Hodgkin's disease of a B-cell immunophenotype to detect rearranged immunoglobulin variable-region heavy-chain (VH) genes.

METHODS

We isolated single Reed-Sternberg cells from frozen sections that had been immunostained for CD30. The rearranged VH genes of these cells were amplified by the polymerase chain reaction and analyzed by gel electrophoresis and nucleotide sequencing.

RESULTS

In all 12 patients, the Reed-Sternberg cells studied contained rearranged VH genes. Three patterns were observed: in three patients the rearrangements in each patient were identical, in six patients all the rearrangements were unrelated and unique, and in three patients both identical and unrelated rearrangements were detected. Apparently somatic mutations of VH genes were present in some Reed-Sternberg cells but absent in others.

CONCLUSIONS

Reed-Sternberg cells with B-cell phenotypes have rearranged VH genes; therefore, these cells arise from B cells. The pattern of VH gene mutations suggests that Reed-Sternberg cells can correspond to either immunologically naive or memory B cells. In half our patients the population of Reed-Sternberg cells was polyclonal; in the other half, monoclonal or mixed cell populations were found. Correlation with the clinical stage suggests that polyclonal Hodgkin's disease can present as a widespread lymphoma.