Elevated expression of Cu, Zn-SOD and Mn-SOD mRNA in inflamed dental pulp tissue

AIM

To determine the mRNA expression levels of copper-zinc superoxide dismutase (Cu, Zn-SOD) and manganese SOD (Mn-SOD) in healthy and inflamed human dental pulp tissue.

METHODOLOGY

Sixteen patients with symptomatic irreversible pulpitis (eight females and eight males) were selected for study. Normal healthy pulps were removed from extracted mandibular third molar teeth from 10 systemically healthy individuals (six females and four males). QRT-PCR analysis of Cu, Zn-SOD and Mn-SOD mRNA expression was carried out in 16 cases of irreversible pulpitis and in 10 cases of systemically healthy donors. The Shapiro-Wilk's test was used to test the normality of data, whereas the Mann-Whitney U-test was used to evaluate the significance of the differences between groups. Differences in the expression levels were considered to be statistically significant for P-values <0.05.

RESULTS

A significant increase (P < 0.05) occurred in both Cu, Zn-SOD and Mn-SOD mRNA expression in cases of irreversible pulpitis. The increase in Mn-SOD level was significantly higher (P < 0.05) than the change observed for Cu, Zn-SOD.

CONCLUSIONS

The development of pulpitis is associated with elevated transcription of both Cu, Zn-SOD and Mn-SOD; pulp tissue inflammation generated higher Mn-SOD transcription compared with Cu, Zn-SOD.

Richter's and prolymphocytic transformation of chronic lymphocytic leukemia are associated with high mRNA expression of activation-induced cytidine deaminase and aberrant somatic hypermutation

Chronic lymphocytic leukemia (CLL) is an indolent B-cell non-Hodgkin's lymphoma that may transform into higher-grade lymphoma. The transformation involves an increased number of prolymphocytic cells, termed prolymphocytic transformation (PLT) or the development of diffuse large B-cell lymphoma (DLBL), also referred to as Richter's transformation (RT). To analyze whether activation-induced cytidine deaminase (AID), which is essential for somatic hypermutation (SHM) of normal B-cells, and malfunction of SHM termed aberrant somatic hypermutation (ASHM) are associated with higher-grade transformation of CLL, AID mRNA expression and the mutation pattern of c-MYC, PAX-5 and RhoH genes were analyzed in eight cases of CLL without transformation and in 21 cases that showed RT or PLT. Chronic lymphocytic leukemia cases, which showed no transformation or eventually transformed into higher-grade lymphoma, showed low levels of AID mRNA expression and low frequency of mutations of c-MYC, PAX-5 and RhoH genes. In both RT and PLT, high-levels of AID mRNA expression and high-frequency mutations of c-MYC, PAX-5 and RhoH genes were detected. These results indicate that AID expression and ASHM are associated with higher-grade transformation of CLL and provide further evidences that AID expression and ASHM may be activated during the clonal history of B-cell lymphomas.

Prognostic significance and detection of the internal tandem duplication of the FLT3 gene in acute myeloid leukemia

The FMS-like tyrosine kinase-3 (FLT3), which belongs to the class III receptor tyrosine kinase family, expressed by immature hematopoietic cells, plays an important role in the proliferation, differentiation and survival of stem cells. The activating mutations of FLT3 gene have been reported to be of prognostic significance. The most common somatic alteration of the FLT3 gene is the Internal Tandem Duplication (FLT3/ITD), which is caused by the elongation of the juxtamembrane (JM) domain of FLT3. The duplicated fragment size varies from 3 to more than 400 base pair, always occurs in multiples of three while the reading frame is preserved. The elongated segment of DNA can be amplified by polymerase chain reaction (PCR), and the products are separated by gel electrophoresis. The FLT3/ITD is found in 20-40% of adult AML patients and is the most frequent mutation in leukemia. Using native peripheral blood and bone marrow from AML and non-AML patients (total of 19 samples), and samples from the RNA bank (total of eight samples), the authors purpose was to work out a method for FLT3/ITD detection, which can be used in routine diagnostics. All samples produced detectable PCR products, which proofs that this procedure can be used for the detection of FLT3/ITD mutations in daily clinical practice.

Clonal selection in the bone marrow involvement of follicular lymphoma

To characterize the pathways of bone marrow (BM) involvement of follicular lymphoma (FL), we performed morphological and immunophenotypical analysis of tumor cells from lymph nodes (LNs) and corresponding BMs in 21 patients with FL. In three cases, genealogical trees were constructed based on the immunoglobulin variable region heavy chain (IgV(H)) gene sequences of tumor clones from LNs and BMs. Results showed that FLs within the BMs display identical or lower cytological grades than in the LNs. In the majority of cases, different proportions of tumor cells expressed bcl-2, CD10 and Ki67 in LNs and BMs. Tumor cells in the BM showed ongoing somatic hypermutation of the IgV(H) genes; the distribution of these mutations was highly consistent with antigen selection. The topology of the genealogical trees revealed that different subclones populate the LN and BM and BM infiltration may occur at different points of the clonal evolution of FL. Early descendants of the original tumor clone and derivatives of diversified tumor clones may invade the BM. These results suggest that the BM involvement of FL is associated with intensive clonal selection of tumor cells, and the BM provides a microenvironment similar to the germinal centers of LNs, where tumor cells retain their biological nature.

Relationship between the mutational status of VH genes and pathogenesis of diffuse large B-cell lymphoma in Richter's syndrome

Patients with chronic lymphocytic leukemia (CLL) may develop diffuse large B-cell lymphoma (DLBL), also known as Richter's syndrome. Mutational status of immunoglobulin (Ig) heavy-chain variable region (VH) genes have prognostic impact in CLL. Patients with mutated VH genes have a stable disease, whereas patients with unmutated VH gene have more aggressive disease. The mutational status of CLLs that transform to DLBL is unknown. To reveal whether Richter's syndrome occurs in CLLs with mutated or unmutated VH genes, we have performed mutational analysis on serial specimens from eight patients. CLL and DLBL tumorclones were identical in five cases and they were different in three cases. Six CLLs expressed unmutated and two cases expressed mutated VH genes. In five of the six unmutated CLLs, the DLBL clones evolved from CLL tumorclones and the VH genes expressed by DLBLs were also unmutated. In one unmutated and two mutated CLLs, the DLBLs expressed mutated VH genes, but in these three cases the DLBL tumorclones developed as independent secondary neoplasm. These results suggest that Richter's syndrome may develop in both mutated or unmutated CLLs, but clonal transformation of CLL to DLBL occur only in the unmutated subgroup of CLL.

Microsatellite instability and hMLH1 promoter hypermethylation in Richter's transformation of chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is an indolent B cell non-Hodgkin lymphoma (NHL) that may transform into diffuse large B cell lymphoma (DLBL). This transformation is referred to as Richter's syndrome or transformation. To analyze whether microsatellite instability (MSI) and DNA mismatch repair defects are associated with Richter's transformation, we have performed microsatellite analysis, mutational analysis of hMLH1 and hMSH2 genes and methylation status analysis of CpG island of the hMLH1 promoter on serial biopsy specimens from 19 patients with CLL. Ten cases of CLL showed no histologic alteration in the second biopsy, and nine cases of CLL underwent morphologic transformation to DLBL in the second biopsy. Using eight microsatellite loci, high level of MSI was associated with Richter's transformation in four cases of CLL, but none of the CLLs displayed this level of MSI without transformation. Mutations of the hMLH1 or hMSH2 genes were not detected in any of the lymphoma samples. In five cases of Richter's transformation the hMLH1 promoter was hypermethylated in both CLL and DLBL samples. Hypermethylation of the hMLH1 promoter associated with high-level of MSI in four cases, and low-level of MSI in one case. These results suggest that in certain cases of Richter's transformation the DNA mismatch-repair defect-initiated genetic instability may play a role in tumor progression.

[The World Health Organization classification of lymphoid neoplasms]

The European Society of Pathology and the Society for Hematopathology have developed a new World Health Organization (WHO) classification of hematological malignancies. The classification is based on the principle that the classification is a list of entities defined by the combination of morphology, immunophenotype, genetic and clinical features. The WHO classification is a new basis of communications between pathologist and oncologist which will help to understand and treat hematological malignancies

Genetic instability is associated with histological transformation of follicle center lymphoma

Follicle center lymphoma (FCL) is an indolent B cell non-Hodgkin's lymphoma (NHL) characterized genetically by the t(14;18) translocation. Histological transformation and clinical progression of FCLs are frequently associated with secondary genetic alterations at both nucleic acid and chromosomal levels. To determine the type and pattern of genomic instability occurring in histological transformation of FCLs and the role of DNA mismatch repair defects in this procedure, we have performed microsatellite analysis, comparative genomic hybridization (CGH) and mutational analysis of hMLH1 and hMSH2 genes on serial biopsy specimens from patients with FCL transformed to diffuse large cell lymphoma (DLCL). Paired biopsy samples of eight patients were analyzed for microsatellite instability and structural alterations for hMLH1 and hMSH2 genes, and tumor samples of five patients were subjected to CGH analysis. A high level of microsatellite instability was associated with histological transformation of two cases of FCL, but no mutations of the hMLH1 and hMSH2 genes were detected in any of the lymphoma samples. In the five cases subjected to CGH analysis, the histological transformation of FCLs was associated with genomic imbalances at 21 chromosomal regions. The genomic abnormalities found were rather heterogeneous and none of the genetic changes were overrepresented in the transformed DLCLs. These data suggest that histological transformation of FCLs to DLCL is frequently associated with genome wide instability at both nucleic acid and chromosomal levels, although mutations of the hMSH1 and hMLH2 genes are not involved in this process.

Sporadic p53 mutations and absence of ras mutations in glioblastomas

As concerns human adult brain neoplasms, the biological behaviour of glioblastoma, a high-grade neuro-ectodermal tumour, is among the most disadvantageous. Glioblastoma may develop either as a primary tumour without clinical and histological evidence of a prior precursor lesion, or as the final stage of malignant transformation of a low-grade or anaplastic astrocytoma. There are conflicting reports in connection with the association of the p53 tumour suppressor gene mutation with the clinical and histological progression of gliomas. Previous studies likewise led to contradictory results concerning the significance of ras oncogenes in different histological malignancies, and especially in neuro-epithelial tumours. The possible roles of p53 and ras gene alterations in the development of "primary" and "transformed" glioblastomas were studied in this work. Eighteen tumours were investigated by means of immunohistochemistry and polymerase chain reaction-assisted-single strand conformation polymorphism (PCR-SSCP) sequence analysis in a search for molecular genetic differences between primary and transformed glioblastomas. An increased incidence of p53-immunopositive cells was observed in both types of glioblastomas but there was no significant difference between the transformed tumours and the primary form. All samples were screened for point mutation in codons 12 and 61 of the H-, K-, and N-ras oncogenes and exons 5-8 of the p53 gene. No aberrant band or mutation was found in the H-, K- and N-ras oncogenes. Aberrant bands were seen in only 2 (11%) of the 18 tumours in the SSCP analyses of exons 6 and 8. Sequence analysis of the 2 abnormal cases revealed G --> C transmission in the second nucleotide of codon 280 on exon 8, which resulted in a change in the encoded amino acid from arginine to threonine (case 15). A ttagtct --> ttggtct transmission on intron 5 (case 8) was also found. No genetic difference could be identified between the primary and the transformed glioblastoma forms as concerns their p53 and ras oncogenes. There are two possible explanations for these findings: (a) The p53 and ras gene mutations were not primary events in the morphological transformations. Alterations in these genes may therefore take place at an early stage in glioma progression. (b) The different genetic changes may accumulate during glioblastoma development. These specific genetic events may additionally play a role in multistep tumourigenesis.

[Detection of minimal residual diseases in B-cell tumors using PCR specific for the immunoglobulin heavy chain gene]

In B-cell non-Hodgkin's lymphomas (NHL), clonal rearrangement of the immunoglobulin heavy chain (IgH) gene provides a useful marker for the detection of minimal residual disease (MRD) after treatment. To explore clinical usefulness of polymerase chain reaction (PCR) analysis of clonal IgH gene rearrangement in the detection of MRD a follow up study of 10 patients with B-cell NHL have been performed. At the time of diagnosis, tumor DNAs were PCR-amplified using sense primer specific for the heavy chain variable region (VH) and antisense primer specific for the heavy chain joining region (JH) of the IgH gene. The clonal rearrangement of IgH gene detected by PCR was used as clonal marker to determine MRD after treatment. In three cases, where clinical remission was not achieved, clonal IgH gene rearrangement was detected after the treatment. In seven cases, clinical remission was achieved after induction therapy but the PCR analysis revealed clonal IgH gene rearrangement in three of the cases. In all of the three cases, where MRD was detected by PCR, clinical relapse developed after 7-28 months of the therapy. In all cases that have relapsed, the IgH gene rearrangement was identical at the time of initial diagnosis and at the relapse. This study demonstrates that PCR analysis of clonal IgH gene rearrangement is a useful method to monitor and detect MRD before clinical relapse.

Somatic mutation of the 5' noncoding region of the BCL-6 gene is associated with intraclonal diversity and clonal selection in histological transformation of follicular lymphoma

Follicular lymphoma (FL) is a B cell non-Hodgkin's lymphoma (NHL) that frequently displays a t(14;18) translocation. Clonal evolution and histological transformation of FL is frequently associated with the accumulation of secondary genetic alterations. It has been demonstrated that the BCL-6 gene can be altered by chromosomal rearrangements and by mutations clustering in its 5' noncoding region in a significant fraction of FL and diffuse large cell lymphoma (DLCL). To elucidate the role of the BCL-6 gene alterations in the histological transformation and clonal progression of FL, we analyzed serial biopsy specimens from 12 patients with FL. Two cases of FL showed no histological alteration in the second biopsy, and 10 cases of FL showed morphological transformation to DLCL in the second biopsy. Southern blot analysis was used to detect rearrangement of the BCL-6 gene, polymerase chain reaction-single strand conformation polymorphism and sequence analysis were performed for identification of mutations in the 5' noncoding region of the BCL-6 gene, and immunohistochemical analysis was applied to reveal the BCL-6 protein expression. No BCL-6 gene rearrangement was detected in any of the samples, but a total of 58 mutations were found in the 5' noncoding region of the BCL-6 gene in seven cases. In five cases, both the FL and the clonally related FL or DLCL, and in two cases only the DLCL samples were mutated. The mutations were identical in multiple biopsy specimens of FL that did not show morphological transformation. In six patients where FL cells underwent morphological transformation, considerable intraclonal sequence heterogeneity was observed, indicating an ongoing type of somatic mutation. Based on the pattern of shared and nonshared mutations, the genealogical relationship of neoplastic clones could be established. In all of these cases, the histological transformation of FL was associated with the emergence of a subpopulation marked by new sites of mutations in the BCL-6 5' noncoding sequences. In three of these six cases, the histological transformation is also associated with the reduced expression of the BCL-6 protein. These findings demonstrate that mutation of the 5' noncoding region of the BCL-6 gene developed in the clonal evolution of FL, and at different time points in the lymphoma evolution different clonotypes dominate.

Immunoglobulin V(H) gene mutational analysis suggests that blastic variant of mantle cell lymphoma derives from different stages of B-cell maturation

To characterise the nature of the cellular origin of the blastic variant of mantle cell lymphoma (MCL-BV), we analysed the immunoglobulin (Ig) heavy chain variable region (V(H)) genes in four cases of MCL-BV. The rearranged V(H)-D J(H) genes were PCR-amplified, cloned and sequenced. In one case, the comparison of the rearranged V(H) gene sequence to known germline V(H) gene templates showed no somatic mutations suggesting a pre-germinal centre B-cell origin for tumour cells. In the other three cases, the V(H) gene sequences showed varied number of point mutations relative to the putative germline V(H) gene sequences but the point mutations were not associated with intraclonal diversification. In one of the mutated cases, the distribution and type of the mutations indicated that tumour cells had been selected by an antigen. Since somatically mutated Ig genes are expressed by B-cells that have reached a germinal centre/post-germinal centre stage of development, these findings suggest that the MCL-BV cell of origin may also be a germinal centre or a post-germinal centre B-cell. Taken together, our findings suggest that the development of MCL-BC may not be restricted to one stage of B-cell differentiation and that they may represent transformants of B-cells at different stages of ontogeny.