Analysis Of X-chromosome Inactivation Patterns Research Articles

Demonstration of developing myelodysplasia/acute myeloid leukaemia in haematologically normal patients after high‐dose chemotherapy and autologous bone marrow transplantation using X‐chromosome inactivation patterns

Autologous bone marrow or peripheral blood stem cell transplantation may carry an increased risk of secondary myelodysplasia (MDS) and acute myeloid leukaemia (AML), which are already recognized as complications of conventional treatment for lymphoid malignancies. In order to ascertain whether it is possible to detect the evolution of such a clone at an early stage in its development we have studied X-chromosome inactivation patterns (XCIPs) in three informative females who developed abnormal myelopoiesis after high-dose chemotherapy and ABMT. In one patient transplanted for relapsed Hodgkin's disease a leukaemic clone comprising approximately 50% of the patient's myeloid cells was detectable by comparison of peripheral blood granulocyte and T-cell XCIPs when the full blood count and morphology were normal. She presented with AML 7 months later. In two patients transplanted for AML, XCIP analysis was complicated by constitutively skewed Lyonization patterns, nevertheless a progressive alteration could be demonstrated by serial analyses. In one patient a difference was detectable 28 months before presentation with MDS. In the other patient, despite evident mild pancytopenia and alterations in her XCIPs over the past 4 years, she has developed no definitive myelodysplastic features and oligoclonality due to stem cell failure cannot be excluded. These studies show that XCIPs can be used to predict development of MDS/AML in some patients, but the technique is limited by technical variability and frequent constitutional skewing in the haemopoietic system.

Clonality in hepatocellular carcinoma: Analysis of methylation pattern of polymorphic X-chromosome-linked phosphoglycerate kinase gene in females

Analysis of X-chromosome inactivation patterns in women has been used to assess the clonality of various tumors. In this report, we analyzed 27 liver tumors in women, including 18 samples obtained by the performance of ultrasonically guided thin-needle biopsies. By analysis of the heterogeneity of phosphoglycerate kinase gene, 11 of 27 (41%) cases were found to be heterozygous at the gene. Of these informative 11 cases with liver tumors, 7 cases were "large" tumors (> 25 mm in diameter) and 4 cases were "small" tumors (< 25 mm in diameter). All 7 large tumors showed monoclonal patterns by the phosphoglycerate kinase gene analysis. Of the 4 small tumors, 2 showed monoclonal, and 2 showed polyclonal patterns. The 2 with monoclonal patterns were pathologically diagnosed as hepatocellular carcinoma despite their small sizes (20 mm and 23 mm). Of the two with polyclonal patterns, the smallest one (15 mm) was diagnosed as benign adenomatous hyperplasia, and the other as hepatocellular carcinoma heavily infiltrated by lymphocytes. These data suggest that analysis of the methylation pattern of the phosphoglycerate kinase gene may be helpful on rare occasions in elucidating the nature of liver tumors but must in fact be used in conjunction with histological appearances to avoid errors secondary to inflammatory infiltrates.

Clonality in hepatocellular carcinoma: Analysis of methylation pattern of polymorphic X-chromosome—linked phosphoglycerate kinase gene in females

Analysis of X-chromosome inactivation patterns in women has been used to assess the clonality of various tumors. In this report, we analyzed 27 liver tumors in women, including 18 samples obtained by the performance of ultrasonically guided thin-needle biopsies. By analysis of the heterogeneity of phosphoglycerate kinase gene, 11 of 27 (41%) cases were found to be heterozygous at the gene. Of these informative 11 cases with liver tumors, 7 cases were “large” tumors (>25 mm in diameter) and 4 cases were “small” tumors (<25 mm in diameter). All 7 large tumors showed monoclonal patterns by the phosphoglycerate kinase gene analysis. Of the 4 small tumors, 2 showed monoclonal, and 2 showed polyclonal patterns. The 2 with monoclonal patterns were pathologically diagnosed as hepatocellular carcinoma despite their small sizes (20 mm and 23 mm). Of the two with polyclonal patterns, the smallest one (15 mm) was diagnosed as benign adenomatous hyperplasia, and the other as hepatocellular carcinoma heavily infiltrated by lymphocytes. These data suggest that analysis of the methylation pattern of the phosphoglycerate kinase gene may be helpful on rare occasions in elucidating the nature of liver tumors but must in fact be used in conjunction with histological appearances to avoid errors secondary to inflammatory infiltrates.

Tissue Specificity of X-Chromosome Inactivation Patterns

AbstractThe analysis of X-chromosome inactivation patterns has been used in a number of clinical situations such as the identification of carrier status in X-linked genetic disorders and the establishment of the monoclonal origin of tumors. Interpretation of the result obtained requires comparison with the constitutive pattern for the individual, and for hematopoietic malignancies, skin biopsies or cultured fibroblasts have often been used as the control tissue because normal cells of the same lineage as the malignancy are not generally available. However, this assumes that patterns in the different tissues are constitutionally the same. We have therefore compared X-chromosome inactivation patterns from peripheral blood (granulocytes, E- cells, and T cells), skin, and muscle from 20 hematologically normal females, and colonic mucosa from 9 individuals. In 11 patients (55%), the results obtained were similar for all tissues of an individual, but in 9 patients, significant differences were observed between tissues. The most consistent feature was a skewing in peripheral blood (>75% expression of one allele) but not skin and/or muscle. These studies suggest that skin cannot be used as a control tissue for the interpretation of X-chromosome inactivation patterns in hematopoietic cells.

Frequency of clonal remission in acute myeloid leukaemia

Analysis of X-chromosome inactivation patterns in females has been used to assess clonality of various tumours and for prenatal diagnosis of X-linked disorders. Studies with these methods in acute myeloid leukaemia suggest that a significant proportion of cases have clonal remissions (ie, persistence of the malignant clone), which may represent return to a preleukaemic state. We therefore analysed X-chromosome inactivation patterns with differential methylation patterns of heterozygotes for three DNA probes, HPRT, PGK, and M27β, in leukaemic patients and normal controls. As expected, blast cells from 67 of 68 analysable samples (99%) were monoclonal or had a skewed X-inactivation pattern. A skewed pattern in remission was also found in 26 of 77 patients (34%), proportion only slightly greater than control (16/75, 21%). In 7 of 10 patients with a skewed pattern in myeloid cells there was similar skewing in the T cells, which is compatible with the concept of a constitutively skewed X-chromosome inactivation pattern of haemopoietic cells in these patients. Our study illustrates the difficulty of interpreting clonality in individual tumour samples and emphasises the importance of comparisons with non-malignant tissue of the same cell type from that individual and from normal control populations.