Assessment of the transcriptional activity of p53 improves the prediction of recurrence in superficial transitional cell carcinoma of the bladder

Clinical aspects of TP53 gene inactivation in diffuse large B-cell lymphoma

Background

The knowledge about specific mechanisms generating TP53 dysfunction in diffuse large B-cell lymphoma is limited. The aim of the current study was to comprehensively explore TP53 gene variability resulting from somatic mutations, promoter methylation, and allelic imbalance in tumorous tissue of diffuse large B-cell lymphoma (DLBCL).

Methods

DNA samples from 74 patients with DLBCL were used. Genomic DNA was isolated from paraffin blocks of lymph nodes or from extranodal biopsies of tumors by the phenol–chloroform extraction method with guanidine. Analysis of coding sequences of the TP53 gene was based on Sanger’s direct sequencing method. The methylation status of the TP53 promoter was analyzed using by methylation-specific PCR on bisulfite-converted DNA. Assessment of the detected mutations was carried out in the IARC TP53 Database and the TP53 UMD mutation database of human cancer.

Results

The mutations in regions coding for the DNA-binding domain were prevalent (95%). In the analyzed sample of patients, codons 275, 155, 272, and 212 were hotspots of mutations in the TP53 gene. In addition, functionally significant intron mutations (IVS6-36G > C and IVS5 + 43G > T) were detected. Instances of TP53 promoter methylation were observed only in a few samples of diffuse large B-cell lymphoma tissue. Furthermore, loss of heterozygosity was revealed only in the subgroup of patients with altered status of the gene (mutations were detected in five patients and promoter methylation in one case).

Conclusions

Thus, the results suggest that there are two sequential events in the formation of diffuse large B-cell lymphoma in at least some cases. The first event is mutation or methylation of the TP53 promoter, leading to appearance of a cell with increased risk of malignant transformation. The second event is the loss of an intact allele of the gene; this change is necessary for tumorigenesis. We identified TP53 mutation patterns in a Russian cohort of patients with de novo DLBCL who were treated with R-CHOP and R-CHOP-like regimens and confirmed that TP53 mutation status is a valuable prognostic biomarker.

Unambiguous detection of multiple TP53 gene mutations in AAN-associated urothelial cancer in Belgium using laser capture microdissection

In the Balkan and Taiwan, the relationship between exposure to aristolochic acid and risk of urothelial neoplasms was inferred from the A>T genetic hallmark in TP53 gene from malignant cells. This study aimed to characterize the TP53 mutational spectrum in urothelial cancers consecutive to Aristolochic Acid Nephropathy in Belgium. Serial frozen tumor sections from female patients (n = 5) exposed to aristolochic acid during weight-loss regimen were alternatively used either for p53 immunostaining or laser microdissection. Tissue areas with at least 60% p53-positive nuclei were selected for microdissecting sections according to p53-positive matching areas. All areas appeared to be carcinoma in situ. After DNA extraction, mutations in the TP53 hot spot region (exons 5–8) were identified using nested-PCR and sequencing. False-negative controls consisted in microdissecting fresh-frozen tumor tissues both from a patient with a Li-Fraumeni syndrome who carried a p53 constitutional mutation, and from KRas mutated adenocarcinomas. To rule out false-positive results potentially generated by microdissection and nested-PCR, a phenacetin-associated urothelial carcinoma and normal fresh ureteral tissues (n = 4) were processed with high laser power. No unexpected results being identified, molecular analysis was pursued on malignant tissues, showing at least one mutation in all (six different mutations in two) patients, with 13/16 exonic (nonsense, 2; missense, 11) and 3/16 intronic (one splice site) mutations. They were distributed as transitions (n = 7) or transversions (n = 9), with an equal prevalence of A>T and G>T (3/16 each). While current results are in line with A>T prevalence previously reported in Balkan and Taiwan studies, they also demonstrate that multiple mutations in the TP53 hot spot region and a high frequency of G>T transversion appear as a complementary signature reflecting the toxicity of a cumulative dose of aristolochic acid ingested over a short period of time.

Expression of p53 family genes in urinary bladder cancer: correlation with disease aggressiveness and recurrence

p53 is a tumour suppressor gene with an established role in the majority of human neoplasias. Its homologues-p63 and p73-cannot be classified as tumour suppressors, since they encode isoforms with oncogenic properties as well. p63 plays a crucial role in epithelial cell differentiation and p73 is essential for neuronal cell development. The p63 and p73 expressions have been investigated in a variety of human tumours including bladder carcinomas; yet, this is the first study to simultaneously analyse the transcriptional levels of all p53 family members in bladder cancer. Using quantitative real-time polymerase chain reaction, we measured the mRNA expression of p53, p63 and p73 in 30 bladder tumours, each paired with adjacent normal tissue. All three studied genes were up-regulated in malignant specimens, p53 by 1.9-fold, p63 by threefold and p73 by twofold, respectively. Further analysis suggested that p63 and p73 act independently of p53 in the malignant bladder epithelium. Statistical analysis revealed that p63 overexpression was more frequent in recurrent bladder tumours (p = 0.045) and in older patients (p = 0.022). Papillary tumours also exhibited abnormal p63 expression (p = 0.026). Finally, p73 was up-regulated in Grade III one-site tumours (p = 0.040). Our results indicate that all p53 family members are abnormally expressed in bladder cancer but do not act synergistically. High levels of p63 correlate with non-muscle invasive tumours with frequent relapses, whereas p73 overexpression is associated with a more aggressive tumour phenotype.

Human umbilical cord matrix stem cells maintain multilineage differentiation abilities and do not transform during long-term culture

Umbilical cord matrix stem cells (UCMSC) have generated great interest in various therapeutic approaches, including liver regeneration. This article aims to analyze the specific characteristics and the potential occurrence of premalignant alterations of UCMSC during long-term expansion, which are important issues for clinical applications. UCMSC were isolated from the umbilical cord of 14 full-term newborns and expanded in vitro until senescence. We examined the long-term growth potential, senescence characteristics, immunophenotype and multilineage differentiation capacity of these cells. In addition, their genetic stability was assessed through karyotyping, telomerase maintenance mechanisms and analysis of expression and functionality of cell cycle regulation genes. The tumorigenic potential was also studied in immunocompromised mice. In vitro, UCMSC reached up to 33.7±2.1 cumulative population doublings before entering replicative senescence. Their immunophenotype and differentiation potential, notably into hepatocyte-like cells, remained stable over time. Cytogenetic analyses did not reveal any chromosomal abnormality and the expression of oncogenes was not induced. Telomere maintenance mechanisms were not activated. Just as UCMSC lacked transformed features in vitro, they could not give rise to tumors in vivo. UCMSC could be expanded in long-term cultures while maintaining stable genetic features and endodermal differentiation potential. UCMSC therefore represent safe candidates for liver regenerative medicine.

Assessment of p53 functional activity in tumor cells and histologically normal mucosa from patients with head and neck squamous cell carcinoma

BACKGROUND

The purpose of this study was to investigate the value of p53 functional analysis of separated alleles in yeast (FASAY) as a witness of p53/p21 pathway alteration in head and neck squamous cell carcinoma (HNSCC).

METHODS

The p53 transcriptional activity was prospectively analyzed in 82 newly diagnosed patients with HNSCC. FASAY and p53 immunostaining were carried out on paired tumoral and histologically normal tissues. The predictive value of FASAY for locoregional recurrence was assessed by Cox survival analysis.

RESULTS

Loss of p53/p21 transcriptional activity was encountered in 88% tumoral and 18% histologically normal samples, associated with mutations (79%) and insertions/deletions (21%). The p53 overexpression underestimated p53 transcriptional abnormalities. FASAY-positive histologically normal mucosa was significantly associated with locoregional recurrence.

CONCLUSION

FASAY positivity indicates field cancerization in a subgroup of patients with HNSCC, in which nonfunctional p53 was significantly associated with locoregional recurrence. This prompted us to pursue the study on the p53 functional status of normal mucosa in patients with HNSCC.

Automated cell disruption is a reliable and effective method of isolating RNA from fresh snap-frozen normal and malignant oral mucosa samples

: This study compared automated vs. manual tissue grinding in terms of RNA yield obtained from oral mucosa biopsies.

: A total of 20 patients undergoing uvulectomy for sleep-related disorders and 10 patients undergoing biopsy for head and neck squamous cell carcinoma were enrolled in the study. Samples were collected, snap-frozen in liquid nitrogen, and divided into two parts of similar weight. Sample grinding was performed on one sample from each pair, either manually or using an automated cell disruptor. The performance and efficacy of each homogenization approach was compared in terms of total RNA yield (spectrophotometry, fluorometry), mRNA quantity [densitometry of specific

: Although spectrophotometry and fluorometry results were comparable for both homogenization methods,

: Automated tissue homogenization appears to be a versatile, quick, and reliable method of cell disruption and is especially useful in the case of small malignant samples, which show unreliable results when processed by manual homogenization.

Clin Chem Lab Med 2009;47:294–301.

Preservation of RNA for functional analysis of separated alleles in yeast: comparison of snap-frozen and RNALater solid tissue storage methods

BACKGROUND

The aim of the present study was to compare RNALater with the usual method of liquid nitrogen snap freezing as a surrogate mRNA preservation method for functional analysis of separated alleles in yeast (FASAY).

METHODS

A total of 81 patients with transitional cell carcinoma of the bladder underwent fresh tissue biopsies directly transferred into RNALater and stored at room temperature or at 4 degrees C for increasing time intervals until RNA processing. From this cohort of patients, 53 paired snap-frozen and RNALater preservative-suspended tissues were obtained. Samples immediately frozen in liquid nitrogen were further stored at -80 degrees C.

RESULTS

Of the 81 RNALater samples, 14 were not processed for FASAY because of RNA degradation. Of the remaining 67 samples, 15 (22%) were FASAY-positive. Identical FASAY results were found for 50 of 53 (94.4%) paired samples and the percentage of red yeast colonies was highly correlated (Cohen's kappa<0.82; p<0.00001). A single p53 missense mutation was found in each of the three discordant positive FASAY and was identical in each concordant positive sample (10/53). Storing samples in RNALater at room temperature for 3 days and at 4 degrees C for less than 1 month provided high-quality mRNA suitable for FASAY.

CONCLUSIONS

Our results demonstrate that RNALater is a suitable and flexible alternative to snap freezing for FASAY analysis.

Tissue microarray based analysis of prognostic markers in invasive bladder cancer: much effort to no avail?

PURPOSE

To evaluate altered protein expression with tissue microarray methodology for 15 different markers with potential prognostic significance in invasive bladder cancer.

MATERIALS AND METHODS

Invasive tumor was sampled with the tissue-arraying instrument in 133 consecutive patients who underwent radical cystectomy, and at least 3, 0.6-mm tissue cores were obtained. With immunohistochemistry, the expressions of TP53, RB1, CDKN1A (p21), MKI67 (Ki67), PTGS2 (Cox-2), CTNNA1 (alpha-catenin), CTNNB1 (beta-catenin), AKT, PTEN, RHOA, RHOC, STAT1, VEGFC, EGFR, and ERBB2 (HER2) were quantified, and correlations were made with tumor grade, pathologic stage, lymph node status, and disease-specific survival.

RESULTS

Decreased immunohistochemical expression of CTNNA1 and of PTEN correlated with higher pathologic tumor stages (P = 0.01 and P = 0.01, respectively), whereas increased AKT1 and ERBB2 correlated with lower pathologic tumor stages (P = 0.01 and P = 0.03, respectively). Increased RHOA expression was more common in grade 3 than in grade 2 tumors (P = 0.016). There were no other correlations among the 15 factors studied and pathologic stage, lymph node status, or tumor grade. No association was found between bladder cancer death and altered marker status for any of the markers studied.

CONCLUSIONS

Currently, there are reasons to have a skeptical attitude toward the value of tissue microarray based immunohistochemistry as a method for evaluating prognostic markers in invasive bladder cancer. In this study, 15 antibodies were tested but were found to be of little clinical value. Whether this negative finding is related to the group of patients or factors studied, or the methodology is unclear.

Molecular profiling of bladder tumors based on the detection of FGFR3 and TP53 mutations

PURPOSE

On a routine basis we performed systematic molecular screening for FGFR3 and TP53 mutations in 121 bladder tumors. We then specifically analyzed the predictive value of the recurrence of FGFR3 and TP53 genotypes in superficial lesions.

MATERIALS AND METHODS

The FGFR3 gene was analyzed by direct sequencing of exons 7, 10 and 15, whereas TP53 status was determined using the p53 functional assay in yeast.

RESULTS

We identified a missense FGFR3 mutation in 66% of pTa, 26% of pT1 and 12% of pT2 tumors. Of activating FGFR3 mutations 54% and 85% were found in low G1 and intermediate G2 grade tumors, respectively, but in only 20% of high grade G3 tumors. We detected inactivating TP53 mutations in 10% of pTa, 42% of pT1 and 58% of pT2 tumors. Moreover, TP53 mutations were found only in 23% of grade G1 and 3% of grade G2 tumors but in 44% of high grade G3 tumors. When the 2 genotypes were combined, we observed that 58% of pTa tumors had the (mutant FGFR3, WT TP53) genotype, whereas 58% of invasive lesions harbored the inverse genotype (WT FGFR3, mutant TP53). The (mutant FGFR3, WT TP53) genotype and the (WT FGFR3, mutant TP53) genotype were detected in 23% and 38% of pT1G3 tumors, respectively. In the subgroup of 92 patients with superficial pTa-T1 bladder tumors we did not find that the TP53 or FGFR3 genotype alone or combined had a predictive value for tumor recurrence.

CONCLUSIONS

Our data again represent solid proof for the pivotal role of FGFR3 and TP53 mutations in superficial and invasive bladder tumors, respectively. However, other molecular markers should be identified for borderline pT1G3 bladder tumors, which are probably at the crossroads of these 2 distinct molecular pathways.