Mitotic activity and nuclear DNA damage of large cells in Hodgkin's disease: comparison with the expression of p53 and bcl-2 proteins and the presence of Epstein-Barr virus

No Influence of bcl-2, p53, and p21waf1 protein expression on the outcome of pediatric Hodgkin lymphomas

In Argentina, lymphomas account for 13.6% of all pediatric tumors and 47% of them are Hodgkin lymphoma. Previous studies of lymphoma series have reported the expression of apoptotic and cell cycle proteins. Our aim was to study these markers in our pediatric patients and correlate them with their outcome. Immunohistochemical staining with monoclonal antibodies anti-p53, bcl-2, p21, and mdm2 were performed on formalin-fixed paraffin-embedded Hodgkin lymphoma lymph node biopsies from 54 pediatric patients. The analyzed oncogenes p53, bcl-2, p21, and mdm2 exhibited 81%, 44%, 76%, and 90% positive staining, respectively. The most prevalent p53/p21 expression pattern was p53+/p21+, in 57% of cases, whereas concerning p53/mdm2 expression pattern p53+/mdm2+ was observed in 61% of cases. We failed to find any statistically significant correlation between oncogene expression and patient's survival. It seems that p53 plays an important role in lymphomagenesis in our studied population, because it is overexpressed in 81% of Hodgkin lymphoma cases and in more than 50% of cases, it might be able to activate its cellular effectors. Bcl-2 staining observed in 44% of our cases could represent a failure in bcl-2 down-regulation that leads to a rescue event in defective germinal center B-cells, that allows them to develop into Reed-Sternberg and Hodgkin cells.

Proliferation profile of classical Hodgkin's lymphomas. Increased expression of the protein cyclin D2 in Hodgkin's and Reed-Sternberg cells

There is accumulating evidence that Hodgkin's and Reed-Sternberg cells of classical Hodgkin's lymphomas (cHL) display multiple and concurrent alterations in different pathways and checkpoints of the cell cycle. However, the expression of cyclin D2 and its relation to other major cell cycle proteins has not been analyzed in cHL. The aim of the present study was to assess expression of cyclin D2, Ki67, cyclin A, cyclin B1, cyclin D1, cyclin D3, cyclin E, p53, Rb, p16 and p27 proteins in order to gain further insight into the proliferation profile of cHL. Overexpression of cyclin D2 in Hodgkin's and Reed-Sternberg cells was detected in 64/89 (72%) cases of cHL. This finding, in view of recent in vitro data showing that constitutive activation of nuclear factor (NF)-kB could upregulate cyclin D2 expression in part via signal transducer and activator of transcription (STAT)-5a, suggests that induction of cyclin D2 expression may support the proliferation of Hodgkin's and Reed-Sternberg cells. In addition, the present study showed that (1) increased p27 expression status was significantly correlated with higher levels of cyclin A expression (P=0.048) and (2) increased p53 expression status was significantly correlated with higher levels of cyclin A (P<0.001) and cyclin B1 (P=0.040) expression. The association between increased p27 and p53 expression status and higher expression levels of G2/M cyclins suggests that the impairment of the growth inhibitory activity of the p27 and p53 tumor suppressor pathways may promote the proliferation of Hodgkin's and Reed-Sternberg cells.

Hodgkin's lymphoma: the pathologist's viewpoint

Despite its well known histological and clinical features, Hodgkin's lymphoma (HL) has recently been the object of intense research activity, leading to a better understanding of its phenotype, molecular characteristics, histogenesis, and possible mechanisms of lymphomagenesis. There is complete consensus on the B cell derivation of the tumour in most cases, and on the relevance of Epstein-Barr virus infection and defective cytokinesis in at least a proportion of patients. The REAL/WHO classification recognises a basic distinction between lymphocyte predominance HL (LP-HL) and classic HL (CHL), reflecting the differences in clinical presentation and behaviour, morphology, phenotype, and molecular features. CHL has been classified into four subtypes: lymphocyte rich, nodular sclerosing, with mixed cellularity, and lymphocyte depleted. The borders between CHL and anaplastic large cell lymphoma have become sharper, whereas those between LP-HL and T cell rich B cell lymphoma remain ill defined. Treatments adjusted to the pathobiological characteristics of the tumour in at risk patients have been proposed and are on the way to being applied.

Clinical drug-resistant nodular sclerosing Hodgkin's lymphoma is associated with decreased bcl-2 expression in the surrounding lymphocytes and with increased bcl-2 expression in the Reed-Sternberg cells

Identification of patients with Hodgkin's lymphoma who are primary refractory to chemotherapy will have great impact on treatment planning. Several studies have indicated that up-regulation of the bcl-2 proto-oncogene expression in non-Hodgkin's lymphoma can cause resistance to chemotherapeutic drugs. For this reason we investigated the relationship between expression of bcl-2, the pro-apoptotic protein Bax and MIB-1 with clinical drug-resistance in Hodgkin's lymphoma.

METHODS AND RESULTS

Seven patients with nodular sclerosis Hodgkin's lymphoma under 40 years of age, who failed to achieve complete remission upon primary chemotherapy and 10 matched patients who did achieve complete response were selected from the Eindhoven Cancer Registry. Tissue sections from both groups of patients were stained for bcl-2, Bax and MIB-1. In the non-responding patients Reed-Sternberg cells expressed bcl-2 more frequently using a cut-off point of <25% to indicate negative cells (P = 0.04), whereas no differences were observed in the expression of Bax and MIB-1. In non-responding patients the lymphocytes surrounding Reed-Sternberg cells expressed bcl-2 less frequently (P = 0.002), using a cut-off point of < 25%, whereas no difference was observed in the expression of Bax and MIB-1.

CONCLUSION

A high percentage of Reed-Sternberg cells expressing bcl-2 protein and a low expression of bcl-2 proteifi in the surrounding lymphocytes is associated with treatment-failure, and subsequent poor survival in young patients with nodular sclerosing Hodgkin's lymphoma. These results need further validation in larger studies.

Apoptosis of malignant cells in Hodgkin's disease is related to expression of the cdk inhibitor p27KIP1

Previous results from B-cell chronic lymphocytic leukaemia suggest that expression of p27KIP1 might be important in protection from apoptosis. Given the relevance of apoptosis to the pathogenesis of Hodgkin's disease (HD), it was decided to examine the expression of p27KIP1 in relation to apoptosis in these lesions. Paraffin-wax sections from a total of 65 histologically confirmed HD tumours were used to derive apoptotic index (AI) and DNA fragmentation index (DFI) scores, which were compared with the expression of various cell-cycle-regulating proteins, including p27KIP1 (p27), p21WAF1/CIP1 (p21) and cyclin D1, and with Epstein-Barr virus (EBV) status. The DFI was measured by TdT-mediated dUTP-FITC nick end-labelling (TUNEL), and the AI by conventional morphology. Cells showing the typical morphology of apoptosis, together with those resembling so-called 'mummified' Hodgkin/Reed-Sternberg (HRS) cells, were included in AI measurements. Increasing numbers of p27-positive HRS cells were associated with lower levels of apoptosis in these cells, as indicated by significantly lower AI and DFI scores. There was a trend towards poorer survival in those patients with the highest numbers of p27-positive HRS cells and with lower AI and DFI scores, but these differences were not statistically significant. p21-positive HRS cells were significantly more frequent in those cases with lower AI scores. A similar trend was observed for p21 and DFI, although this relationship was not statistically significant. There was also a trend towards higher levels of cyclin D1 protein in HD cases with high AI and DFI values. A tendency for increasing numbers of p27-positive and p21-positive HRS cells in EBV-positive cases was noted, but this relationship was not statistically significant. EBV status did not correlate with either AI or DFI scores. The results of this study suggest that p27, and possibly also p21, may be involved in protection from apoptosis in HD.