Microsatellite instability and k-ras, p53 mutations in thyroid lymphoma

Clinicopathologic features of conjunctival MALT lymphomas refractory to radiation therapy

OBJECTIVE

Clinicopathologic features of patients with limited-stage mucosa-associated lymphoid tissue (MALT) lymphoma refractory to radiotherapy have not been fully elucidated. This study aimed to elucidate clinicopathologic features of localized conjunctival MALT lymphoma concerning radiosensitivity by analyzing cell proliferation and expression of mismatch repair proteins.

METHODS

We enrolled 26 patients with localized conjunctival MALT lymphoma treated with radiotherapy from November 2007 to March 2020. Monoclonal immunoglobulin H gene rearrangement was tested in addition to histopathologic evaluation. Thirty-six specimens were immunostained with antibodies to Ki-67 and MutL protein homologue 1 (MLH1), MutS protein homologue 2 (MSH2), and MutS protein homologue 6 (MSH6). Positive rates under a high-power field at a hot spot were counted manually.

RESULTS

After radiotherapy, 21 patients showed clinical disappearance of the tumour without recurrence (effective group). Three patients showed temporary disappearance of the tumour, which later recurred (relapse group). Two patients did not show disappearance of the tumour (ineffective group). The 2 ineffective patients were young, had bilateral lesions, and received x-ray beam therapy. The mean positive rates of Ki-67, MLH1, MSH2, and MSH6 were higher in tumours with complete remission (CR) than in those without CR (23.4% ± 4.0% and 18.7% ± 4.7%, 14.7% ± 2.3% and 7.1% ± 3.7%, 23.9% ± 4.7% and 14.4% ± 5.2%, and 11.5% ± 3.2% and 5.4% ± 2.2%; p > 0.05 for each, respectively).

CONCLUSIONS

A few patients could not achieve CR following radiotherapy, whereas there were no significant differences in proliferation activity and mismatch repair proteins between tumours with and without CR.

Microsatellite instability (MSI, EMAST) in the pathogenesis of follicular lymphoma

Background. Genetic instability, an important phenomenon involved in oncogenic transformation and tumor progression, is associated with the insufficiency of the multicomponent DNA repair complex, in particular, the nucleotide mismatch repair (MMR) system. The MMR defect manifests itself as abnormalities in DNA microsatellite repeats, or microsatellite instability (MSI). In the studies of colorectal cancer, the role of MSI in prognostication of the disease, and defining the choice of specific therapy with immune checkpoint inhibitors has been proven.

However, in lymphatic system tumors, the significance of this phenomenon is poorly understood. Determination of genetic instability in the onset of follicular lymphoma, a disease characterized by a heterogeneous course, may have prognostic value.

Objective: to determine the genetic instability at the onset of follicular lymphoma.

Materials and methods. Here we report an analysis of 24 microsatellite repeats and amelogenin loci in tumor cells of 46 follicular lymphoma patients.

Results. In the studied cohort, lesions in microsatellite repeats were presented by MSI in 9 cases (19.6 %) and the loss of heterozygosity (LOH) in 19 cases (41.3 %). Most frequent lesions were found for the SE33 marker located at the q14 locus of chromosome 6. A significant association was shown between MSI and the double-hit follicular lymphoma group with rearrangements of the MYC and BCL2/BCL6 genes.

Conclusion. Thus, our data indicate that the MSI phenomenon might be involved in the pathogenesis of the lymphatic tumors and particularly follicular lymphoma. However further studies on the expanded cohorts of patients are required to define the possible prognostic value of MSI in lymphatic tumors.

Effects of prostaglandin E2 on p53 mRNA transcription and p53 mutagenesis during T-cell-independent human B-cell clonal expansion

Within T-cell-dependent germinal centers, p53 gene transcription is repressed by Bcl-6 and is thus less vulnerable to mutation. Malignant lymphomas within inflamed extranodal sites exhibit a relatively high incidence of p53 mutations. The latter might originate from normal B-cell clones manifesting activation-induced cytosine deaminase (AID) and up-regulated p53 following T-cell-independent (TI) stimulation. We here examine p53 gene transcription in such TI clones, with a focus on modulatory effects of prostaglandin E2 (PGE2), and evaluate progeny for p53 mutations. Resting IgM(+)IgD(+)CD27(-) B cells from human tonsils were labeled with CFSE and stimulated in vitro with complement-coated antigen surrogate, IL-4, and BAFF ± exogenous PGE2 (50 nM) or an analog specific for the EP2 PGE2 receptor. We use flow cytometry to measure p53 and AID protein within variably divided blasts, qRT-PCR of p53 mRNA from cultures with or without actinomycin D to monitor mRNA transcription/stability, and single-cell p53 RT-PCR/sequencing to assess progeny for p53 mutations. We report that EP2 signaling triggers increased p53 gene transcriptional activity in AID(+) cycling blasts (P<0.01). Progeny exhibit p53 mutations at a frequency (8.5 × 10(-4)) greater than the baseline error rate (<0.8 × 10(-4)). We conclude that, devoid of the repressive influences of Bcl-6, dividing B lymphoblasts in inflamed tissues should display heightened p53 transcription and increased risk of p53 mutagenesis.

HLA associations, microsatellite instability and epigenetic changes in thyroid lymphoma in Chinese

In Chinese, autoimmune thyroid disease (AITD) is very common but lymphoma of the thyroid is a rare disease. Southern Chinese AITD is common in females and is strongly linked to the HLA haplotype A2B46DR9. We studied the HLA association, aberration p15, p16 and p73 promoter methylation and microsatellite instability in Chinese primary thyroid lymphoma patients to elucidate their relationship with AITD and the relationship between thyroid diffuse large cell lymphoma (DLCL) and marginal zone lymphomas (MZL). Despite a female preponderance (8:1) and the finding of cases with histological and immunological evidence of AITD, a significant HLA association was not found. MSI was absent, but aberrant promoter methylation was found in both thyroid MZL and DLCL and p73 methylation was unexpectedly common.

P53, N- and K-Ras, and beta-catenin gene mutations and prognostic factors in nasal NK/T-cell lymphoma from Hokkaido, Japan

We have shown previously that nasal natural killer (NK)/T-cell lymphoma was associated with Epstein-Barr virus (EBV) and had peculiar clinical features. However, little is known about its biological and genetic changes. The aim of this study is to determine the p53, N- and K-ras, and beta-catenin status in this lymphoma in relation to EBV status and clinical features. The study group consisted of 32 Japanese patients with nasal NK/T-cell lymphoma. The p53 and beta-catenin expression, phenotype, and EBV-oncogenic protein latent membrane protein type 1 (LMP-1) were determined by immunoperoxidase staining. The presence of EBV-encoded small nuclear early region (EBER) RNA was determined by in situ hybridization. The p53 mutations (exons 5 to 9), N- and K-ras mutations (exons 1 and 2), and beta-catenin mutations (exon 3) were analyzed by direct sequencing of the PCR-amplified products that were obtained from laser-microdissected tissues. CD56, CD43, and CD3 were expressed in 32 (100%), in 31 (96%), and in 18 (56%) tumors, respectively. EBER RNA was detected in 31 (96%) tumors. LMP-1 was expressed in 15 (48%) tumors, and p53 and beta-catenin protein were overexpressed in 18 (56%) and 4 (13%) tumors, respectively. Six mutations of the p53 gene, 1 mutation of each N- and K-ras gene, and 8 mutations of beta-catenin gene were detected in 6 (19%), 1 (3%), and 5 (16%) tumors, respectively. The p53 missense mutation was associated with LMP-1 expression (P = 0.038), but not with p53 overexpression. Kaplan-Meier analysis as well as univariate analysis using Cox proportional hazards model showed that high lactate dehydrogenase (LDH) level (P = 0.009, P = 0.0100, respectively), large cell, immunoblastoid polymorphous histology (P = 0.005, P = 0.0162, respectively), and p53 missense mutations (P = 0.021, P = 0.0342, respectively) were significantly related to worse cause-specific survival. Multivariate analysis showed that p53 missense mutation was the most independent among these 3 factors. Although the incidence of thep53, N- and K-ras, and beta-catenin gene mutations is not high, p53 missense mutation has a prognostic value for aggressive course in nasal NK/T-cell lymphoma.

In situ shortening of CAG repeat length within the androgen receptor gene in prostatic cancer and its possible precursors

BACKGROUND

The amino-terminal transcriptional activation domain of the androgen receptor (AR) gene contains two polymorphic trinucleotide repeat segments that encode polyglutamine (CAG)n and polyglycine (GGC)n tracts. Shorter CAG repeat lengths are associated with higher transcriptional activity. The previous studies using peripheral blood leukocytes showed the relationship between shorter CAG repeat length and risk for prostate cancer (PCA).

METHODS

Prostatic cancer (PCA), its possible precursors [high grade prostatic intraepithelial neoplasia (HGPIN) and postatrophic hyperplasia (PAH)], and non-neoplastic epithelium were microdissected from a whole-mount prostatectomy specimen from 34 cases with PCA. DNA extracted from each lesion was processed for PCR-based electrophoresis on 6% denaturing polyacrylamide gels, followed by direct sequencing. To examine whether the in situ shortening of CAG repeat was confined to the CAG repeat or was a part of phenomenon induced by microsatelite instability (MSI), BAT-25 and BAT-26, effective markers for detection of MSI, were also examined.

RESULTS

All non-neoplastic epithelial lesions had identical numbers of CAG repeat in the same prostate. CAG repeat lengths were identical in lesions in 25 cases. Two distinct products were found in 9 of 34 cases (26.5%); one product identical to that of non-neoplastic epithelium and another smaller one. In situ shortening of CAG repeat lengths in PCA, HGPIN, and PAH was found in 3 of 34 (8.8%), 6 of 34 (17.6%), and 3 of 10 (30%) cases, respectively. Frequency of CAG shortening was significantly higher in PAH than in PCA lesions (P < 0.05). The length of GGC repeats, BAT-25 and -26 was identical among all lesions in the same case. There was no significant correlation between shortening of CAG repeat length and the clinicopathologic parameters.

CONCLUSION

Shortening of CAG repeat length was found in in situ lesions of PCA and its possible precursors.

Establishment and characterization of unique cell lines derived from pyothorax-associated lymphoma which develops in long-standing pyothorax and is strongly associated with Epstein-Barr virus infection

Malignant lymphoma frequently develops in the pleural cavity of patients with over 20 years' history of pyothorax. The term pyothorax-associated lymphoma (PAL) has been proposed for this type of tumor. We established four novel lymphoma cell lines (OPL-3, -4, -5, and -7) from four patients with PAL. Characteristics of the four cell lines are as follows: B-cell nature with defective expression of B-cell and T-cell surface antigens, monoclonal pattern of Epstein-Barr virus (EBV) infection in lymphoma cells (thus indicating an etiological role of EBV for lymphomagenesis), complicated chromosomal abnormalities with numerous structural and numerical abnormalities, and occasional but distinct genome instability. These abnormalities in cell character might be caused by the specific circumstances of PAL lymphomagenesis, i.e., chronic inflammation. Thus, PAL cell lines could be useful in analysis of molecular mechanisms leading to malignancy in chronic inflammation.

p53-related pathways and the molecular pathogenesis of melanoma

Cutaneous malignant melanoma (CMM) is a life-threatening cancer that can have a poor prognosis with high metastatic potential. Its incidence is rapidly increasing worldwide. Its molecular alterations involve multiple pathways, including those related to p53. Since 1981, more than 380 papers containing the terms 'p53 and melanoma' as key words in the Abstract have been published in the literature. However, in spite of these extensive investigations, a review of p53 and associated genes in CMM is still lacking. To remedy this issue, this review seeks to provide a brief overview of p53 and discuss the genes targeted along its related pathways.

Analysis of p53, K-ras, c-kit, and beta-catenin gene mutations in sinonasal NK/T cell lymphoma in northeast district of China

Recently we reported the different frequencies of p53 and c-kit gene mutations among sinonasal NK/T cell lymphoma (NKTCL) in Korea, north China (Beijing), and Japan, suggesting some racial, environmental, or life-style differences as a possible cause of nasal tumorigenesis. In this study, gene mutations in p53, c-kit, K-ras, and beta-catenin gene were analyzed by polymerase chain reaction (PCR)-single strand conformation polymorphism (SSCP) followed by direct sequencing in 20 cases of sinonasal NKTCL from northeast China (Shen Yang). Age of patients ranged from 5 to 63 (median, 40.0) years. p53 gene mutations were found in eight of 20 cases (40%), with exon 4 involvement in 10% of cases. The majority was missense mutations and G:C to A:T transition was predominant. The frequency of the c-kit and K-ras gene mutations was low (5%), while that of the beta-catenin gene was six of 20 cases (30%). From these findings, it is concluded that nasal NKTCL in northeast China shared common features with that in Korea in the younger onset of disease compared to that in Japan and lower frequency of p53 gene mutations with infrequent exon 4 involvement compared to that in Japan and north China. These differences might be caused by migration of susceptible populations or some environmental confounding factors.

Gene mutations in lymphoproliferative disorders of T and NK/T cell phenotypes developing in renal transplant patients

Post-transplantation lymphoproliferative disorder (PT-LPD) is characterized by lymphoid proliferation after organ or bone marrow transplantation. In Western countries, most cases of PT-LPD are B-cell-derived and Epstein-Barr virus-associated, in which alterations of c-myc, p53, and N-ras genes might play a role in disease progression. In Japan, PT-LPD of T- and NK/T-cell types are not uncommon in renal transplant patients. Mutations of p53 (exons 4 through 8), K-ras (exons 1 and 2), c-kit (exons 11 and 17), and beta-catenin genes (exon 3) in 12 cases of these diseases were analyzed by PCR single strand conformation polymorphism and then by direct sequencing. p53 gene mutations were detected in 5 of 5 cases of peripheral T-cell lymphoma, 3 (60%) of 5 cases of adult T-cell leukemia/lymphoma, and 1 of 2 cases of NK/T cell lymphoma. Twenty-five percent of T and NK/T cell lymphomas showed K-ras mutations. Mutations of c-kit and beta-catenin genes were found in 33% of cases. Among a total of 42 substitution mutations, 40 were transitions with involvement of CpG sites in 20 to 30% of cases. Most cases had at least one mutation that changed an amino acid, which might have provided the selection pressure for expansion. These findings suggested that p53 gene mutations might play a central role in development of peripheral T-cell lymphoma including adult T-cell leukemia/lymphoma in renal transplant patients.

Mutations of p53, c-kit, K-ras, and beta-catenin gene in non-Hodgkin's lymphoma of adrenal gland

Malignant lymphoma of the adrenal gland is a rare disease, usually with diffuse large cell morphology and B-cell immunophenotype, and often associated with Epstein-Barr virus infection. In this study, mutations of p53, c-kit, K-ras, and beta-catenin gene were analyzed in 17 cases (13 males and four females with ages ranging from 25 to 84 years) of such lymphomas by polymerase chain reaction-single strand conformation polymorphism followed by direct sequencing. Selected exons in each gene, representing hot spots, were analyzed. All 44 mutations detected were single-nucleotide substitutions and 33 were missense mutations. Nineteen mutations were detected in exon 5 and / or 7 of the p53 gene in nine of 17 cases (52.9%) and 21 in exon 11 and / or 17 of the c-kit gene in 10 of 14 cases (71.4%). Bilateral adrenal lesions in one case who had not received any adjuvant therapy showed different mutational patterns of the p53 and c-kit genes, suggesting different clonal evolution of lymphoma between the left and right sides. Mutation at codon 13 of the K-ras gene was detected in one of 14 cases (7.1%), and in exon 3 of the beta-catenin gene in three of 12 cases (25%). All but one mutation were transition mutations, indicating that some endogenous mutagens act in lymphomagenesis in the adrenal gland. Our results suggest that p53 and c-kit gene mutations might play a role in adrenal lymphomagenesis.