beta-Catenin, Nf-kappaB and FAS protein expression are independent events in head and neck cancer: study of their association with clinical parameters

In spite of much effort, no good markers have yet been found for predicting prognosis or response to therapy in advanced head and neck squamous cell carcinoma (HNSCCs) patients. beta-catenin, a protein involved in the cytoskeleton, cell-cell adhesion and gene transcription, is a factor associated with tumour progression. Recently, an interaction has been reported between beta-catenin, and NF-kappaB coupled with an inverse association of beta-catenin, and FAS (CD95/APO-1) protein expression in breast and colorectal tumours. To confirm these observations and to test their clinical impact in HNSCCs we have evaluated the expression of beta-catenin, NF-kappaB and FAS proteins. We used tissue microarrays to simultaneously analyse the levels of these proteins immunohistochemically in 118 HNSCCs. Among the 113 tumours evaluable for beta-catenin, increased and decreased levels were detected in 41 (36%) and 62 (55%) of the tumours, respectively. beta-catenin, protein staining was mainly membranous but 10 tumours (9%) showed the clear presence of protein in the cytoplasm, and none in the nucleus. Moreover, 81% of the tumours had decreased FAS protein expression, indicating that loss of FAS protein is a common feature of HNSCCs. Abnormal or nuclear NF-kappaB staining was observed in 24% of the tumours. No association was detected between the expression levels of the proteins evaluated. Regarding clinical associations, tumours from the hypopharynx had significantly lower levels of beta-catenin expression than those from other locations (P<0.05). Moreover, our data revealed that patients whose tumours had low levels of beta-catenin protein expression had decreased survival probability (24.8 months vs. NR, P=0.03) and reduced response to therapy (15.4 vs. 43 months; P=0.01) compared with patients whose tumours had high levels of beta-catenin. Taken together, our observations indicate that beta-catenin, NF-kappaB and FAS expression are independent events during HNSCC development and that levels of beta-catenin protein may identify subsets of advanced HNSCCs patients with different prognosis and response to therapy capabilities.

Loss of p16/INK4A protein expression in non-Hodgkin's lymphomas is a frequent finding associated with tumor progression

The CDKN2A gene located on chromosome region 9p21 encodes the cyclin-dependent kinase-4 inhibitor p16/INK4A, a negative cell cycle regulator. We analyzed p16/INK4A expression in different types of non-Hodgkin's lymphoma to determine whether the absence of this protein is involved in lymphomagenesis, while also trying to characterize the genetic events underlying this p16/INK4A loss. To this end, we investigated the levels of p16/INK4A protein using immunohistochemical techniques in 153 cases of non-Hodgkin's lymphoma, using as reference the levels found in reactive lymphoid tissue. The existence of gene mutation, CpG island methylation, and allelic loss were investigated in a subset of 26 cases, using single-strand conformational polymorphism and direct sequencing, Southern Blot, polymerase chain reaction, and microsatellite analysis, respectively. Loss of p16/INK4A expression was detected in 41 of the 112 non-Hodgkin's lymphomas studied (37%), all of which corresponded to high-grade tumors. This loss of p16/INK4A was found more frequently in cases showing tumor progression from mucosa-associated lymphoid tissue low-grade lymphomas (31 of 37) or follicular lymphomas (4 of 4) into diffuse large B-cell lymphomas. Analysis of the status of the p16/INK4A gene showed different genetic alterations (methylation of the 5'-CpG island of the p16/INK4A gene, 6 of 23 cases; allelic loss at 9p21, 3 of 16 cases; and nonsense mutation, 1 of 26 cases). In all cases, these events were associated with loss of the p16/INK4A protein. No case that preserved protein expression contained any genetic change. Our results demonstrate that p16/INK4A loss of expression contributes to tumor progression in lymphomas. The most frequent genetic alterations found were 5'-CpG island methylation and allelic loss.

Expression of p21WAF1/CIP1 in fetal and adult tissues: simultaneous analysis with Ki67 and p53

AIMS

To determine the expression of p21WAF1/CIP1 in relation to the expression of Ki67 and p53 in various normal adult and fetal tissues, and to investigate its distribution throughout the cell cycle.

METHODS

The expression of p21WAF1/CIP1 in relation to Ki67 and p53 was analysed in adult and fetal tissues using immunohistochemical techniques. Heat induced epitope retrieval techniques were used to characterise the presence of p21WAF1/CIP1 in different tissues, as well as to detect its distribution throughout the cell cycle. In addition, flow cytometry and western blotting were used to test whether the level of p21WAF1/CIP1 expression varied at different phases of the cell cycle in phytohaemagglutinin (PHA) stimulated lymphocytes.

RESULTS

p21WAF1/CIP1 expression varied from one tissue to another, and it was restricted mainly to the squamous and glandular epithelium, where it appeared in association with p53. Human tissues in which p21WAF1/CIP1 was found showed a mutually exclusive topographical sequential expression between p21WAF1/CIP1 and Ki67. This was confirmed by double labelling studies, which showed that p21WAF1/CIP1 positive cells were in the G0 phase. Unlike these findings of a decline in p21WAF1/CIP1 expression after the G0 phase, PHA stimulated lymphocytes showed a level of p21WAF1/CIP1 expression that rose as the cell progressed through the cell cycle.

CONCLUSIONS

The analysis of p21WAF1/CIP1 expression in relation to the status of p53 should take into account the existence of variable p21WAF1/CIP1 expression in different tissues. This could provide an explanation for the varying frequency of p53 mutations in tumours of different cellular origin. In tissues characterised by regular p21WAF1/CIP1 expression, it appears in a pattern that is consistent with the proposed role of this inhibitor of cyclin dependent kinases in cell cycle arrest-that of inducing cell differentiation. The conflicting results of in vivo and in vitro studies could support the hypothesis that microenvironmental conditions may influence the location of p21WAF1/CIP1 in different phases of the cell cycle.

Mucosal mantle cell (centrocytic) lymphomas

The morphology, phenotype, genotype and clinical behaviour of four cases of mantle cell lymphoma (centrocytic lymphoma) presenting primarily in mucosa (two gastric, one in large bowel and one tonsillar) are reviewed. Their relationship with the broader group of mantle cell and mucosa-associated lymphoid tissue (MALT) lymphomas is also discussed. All four tumours showed a monomorphic picture of mantle cells (centrocytes) arranged in a diffuse, or vaguely nodular, pattern. Scattered non-neoplastic germinal centres were entrapped within the tumour cells, although there was no follicular colonization. In two cases distinct epithelial infiltration by tumour cells was observed. All four tumours had a CD19, CD20, CD5, IgD, Leu8 immunophenotype, whereas KiM1P and CD10 expression were absent. DRC antibody showed loose aggregates of dendritic cells in three of four cases. Three cases showed PRAD-1/Cyclin D1 overexpression by Northern blot analysis. Although we were not able to detect bcl-1 rearrangement in the major translocation cluster (MTC) breakpoint, the possibility of bcl-1 rearrangement involving other cluster breakpoints cannot be ruled out. The four cases evolved as a disseminated disease, involving either peripheral lymph nodes, spleen or bone marrow. The biological behaviour of mantle cell lymphoma presenting in mucosa appears, irrespective of localization or macroscopic presentation, similar to that of nodal mantle cell lymphoma. Their tendency to dissemination contrasts with MALT lymphomas, which tend to remain localized, and from which mucosa mantle cell lymphoma must be distinguished. The presence of lymphoepithelial lesions does not seem to be a useful differential feature, since occasional epithelial infiltration was seen in two cases. Reactivity with CD5 appears to be especially useful in distinguishing these, since all four cases were clearly positive, in contrast with what is usually found in MALT lymphomas.