Differential effects of diverse p53 isoforms on TAp73 transcriptional activity and apoptosis.

The p53 activities are due, at least in part, to its ability to form oligomers that bind to specific DNA sequences and activate transcription. Since some mutant p53 proteins and ΔNp73 isoforms form heterocomplexes with TAp73, we asked whether p53 isoforms can do the same and potentially act as dominant-negative inhibitors of TAp73. Moreover, it has already been found that some isoforms form complex with wtp53 and some of them inhibit p53 tumor-suppressor functions. Therefore, we studied the complex formation and co-immunoprecipitation assays show that all six p53 isoforms examined can form complexes with TAp73ß, whereas only Δ133p53α/ß/γ isoforms form complex with TAp73α. All p53 isoforms counteract TAp73ß transactivation function but with different efficiency and in a promoter-dependent manner. Furthermore, apoptotic activity of TAp73ß was augmented by coexpression of p53ß, whereas Δ133p53α and ß inhibit its apoptotic activity most efficiently. We have determined the half-life of different p53 isoforms: p53γ isoform has the shortest half-life, whereas Δ133p53γ has the longest half-life. Inhibitory interactions of two proteins in complex often lead to their stabilization. However, only three isoforms (Δ133p53α, Δ133p53ß and Δ40p53α) stabilize TAp73ß. We are convinced that defining the interactions between p53/p73 would give a new insight into how the p53 isoforms modulate the p73 functions in tumorigenesis.

The N-terminally truncated p53 isoform Δ40p53 influences prognosis in mucinous ovarian cancer.

OBJECTIVE: The tumor suppressor p53 generates the N-terminally truncated isoforms Δ40p53 and Δ133p53 that possess the ability to modulate p53 function in vitro. The aim of the present study was to evaluate the clinical relevance of p53 isoforms in the main histological subtypes of ovarian cancer. METHODS: Δ40p53, Δ133p53, and full-length p53 (FLp53) expression was determined in 45 mucinous, 30 endometrioid, and 91 serous ovarian cancer specimens as well as 42 normal ovarian tissues using reverse transcriptase-quantitative polymerase chain reaction. In a subgroup of mucinous ovarian cancer cases, Δ40p53 expression was examined using Western blot analysis. A functional yeast-based assay and subsequent sequencing were performed to analyze the p53 mutational status. RESULTS: In endometrioid cancer specimens, Δ133p53 expression was significantly lower than in mucinous and serous cases (P = 0.016) or in normal tissues (P = 0.004). Mucinous cancer samples showed elevated Δ40p53 expression as compared with normal ovarian tissues (P = 0.003). In addition, high Δ40p53 expression constituted an independent prognostic marker for recurrence-free but not for overall survival in patients with mucinous ovarian cancer (hazard ratio, 0.267; 95% confidence interval, 0.094-0.756 [P = 0.013]; hazard ratio, 0.453, 95% confidence interval, 0.193-1.064 [P = 0.069]). Western blot analysis confirmed the presence of p53ß and Δ40p53α in a subset of patients with mucinous ovarian cancer. Expression of p53 isoforms was not associated with p53 mutational status or clinicopathologic parameters. CONCLUSIONS: We show that expression of p53 isoforms differs in histological subtypes, thus supporting the hypothesis that histological subtypes represent distinct disease entities. In addition, we provide first evidence for a favorable role of Δ40p53 in patients with mucinous ovarian cancer.

Extracranial propagation of glioblastoma with extension to pterygomaxillar fossa.

BACKGROUND: Glioblastoma multiforme is a highly malignant primary brain tumor that shows marked local aggressiveness, but extracranial spread is not a common occurrence. We present an unusual case of recurrent glioblastoma in 54-year old male that spread through the scull base to the ethmoid and sphenoid sinuses, to the orbita, pterygomaxillar fossa, and to the neck. METHODS: A 54-year old male underwent left temporal resection because of brain tumor of his left temporal lobe. Operation was followed by external beam radiation combined with temozolomide. The tumor recurred eight months after first surgery. The patient developed swelling of left temporal region, difficult swallowing and headache. MRI of head showed recurrent tumor, which invaded orbita, ethmoid and sphenoid sinuses, nasal cavity, pterygomaxillar fossa. RESULTS: The patient died ten months after initial diagnosis of glioblastoma multiforme, and two months after his second operation. CONCLUSIONS: The aggressive surgical operation helped to downsize the tumor mass as much as possible, but did not prolonged significantly the life or improved the life quality of the patient. The current literature is reviewed, and the diagnostic approaches as well as therapeutic options are discussed.

p53 mutations as fingerprints for aristolochic acid: an environmental carcinogen in endemic (Balkan) nephropathy.

The activation of protooncogenes and inactivation of tumor suppressor genes are considered to be the main molecular events in the multistep process of carcinogenesis. Mutations of the TP53 tumor suppressor gene have been found in nearly all tumor types and are estimated to contribute to more than 50% of all cancers. Most mutations lead to the synthesis of highly stable, inactive proteins that accumulate in the nucleus of cancer cells. Among the 393 codons of the human p53 gene, 222 are targets of 698 different types of mutations. Alterations of codons 175, 248, 273 and 282 correspond to 19% of all mutations and are considered general hot spot mutations. Dietary exposure to aristolochic acid (AA), an established nephrotoxin and human carcinogen found in all Aristolochia species was shown to be the causative agent of aristolochic acid nephropathy (previously called Chinese herbs nephropathy). This syndrome is characterized by proximal tubular damage, renal interstitial fibrosis, slow progression to the end stage renal disease and a high prevalence of upper urinary tract urothelial carcinoma (otherwise a highly unusual location). AA preferentially binds to purines in DNA and is associated with a high frequency of A-->T transversions in the p53 gene. Rats treated with AA develop A:T-->T:A mutations in codon 61. The pathological and clinical features of endemic (Balkan) nephropathy closely resemble those associated with aristolochic acid nephropathy except for the slower progression to end stage renal disease and longer cumulative period before the appearance of urothelial cancer. Recently, we reported the presence of AA-DNA adducts in renal cortex and A-->T p53 mutations in tumor tissue of patients from Croatia and Bosnia with endemic nephropathy. These data support the hypothesis that dietary exposure to AA is a major risk factor for endemic (Balkan) nephropathy.

Cerebellar glioblastomas: pathophysiology, clinical presentation and management.

Glioblastoma multiforme usually affects the cerebral hemispheres with the peak age of onset in the sixth or seventh decade, while cerebellar glioblastoma multiforme is a rare tumour especially in younger patients. Most result from de-differentiation from low grade astrocytoma (secondary glioblastoma) or can develop de novo (primary glioblastoma). Primary glioblastomas develop in older patients while secondary glioblastomas develop in younger patients and contain TP53 mutations as the earliest detectable change. We report a 28 year old patient with primary multi-focal cerebellar glioblastoma multiforme and review the pathophysiology, clinical presentation, diagnosis and treatment of cerebellar glioblastomas.