Mahvash Tavassoli

p53 polymorphism influences response in cancer chemotherapy via modulation of p73-dependent apoptosis

Intact p73 function is shown to be an important determinant of cellular sensitivity to anticancer agents. Inhibition of p73 function by dominant-negative proteins or by mutant p53 abrogates apoptosis and cytotoxicity induced by these agents. A polymorphism encoding either arginine (72R) or proline (72P) at codon 72 of p53 influences inhibition of p73 by a range of p53 mutants identified in squamous cancers. Clinical response following cisplatin-based chemo-radiotherapy for advanced head and neck cancer is influenced by this polymorphism, cancers expressing 72R mutants having lower response rates than those expressing 72P mutants. Polymorphism in p53 may influence individual responsiveness to cancer therapy.

TAT-apoptin is efficiently delivered and induces apoptosis in cancer cells

Apoptin has been described to induce apoptosis in various human cancer cell lines, but not in normal cells, thus making it an interesting candidate for the development of novel therapeutic strategies. Apoptin was generated and cloned into several mammalian expression vectors. Transfection or microinjection of apoptin cDNA resulted in its expression, initially in the cytoplasm with a filamentous pattern. Subsequently, apoptin entered the nucleus and efficiently induced apoptosis in several cancer cell lines. Nuclear localization was shown to be required for induction of apoptosis. Apoptin expression level was found to be an important determinant of the efficiency of induction of apoptosis. Surprisingly, expression of apoptin or GFP-apoptin cDNA induced apoptosis in some normal cells. When fused to the HIV-TAT protein transduction domain and delivered as a protein, TAT-apoptin was transduced efficiently (>90%) into normal and tumour cells. However, TAT-apoptin remained in the cytoplasm and did not kill normal 6689 and 1BR3 fibroblasts. In contrast TAT-apoptin migrated from the cytoplasm to the nucleus of Saos-2 and HSC-3 cancer cells resulting in apoptosis after 24 h. This study shows that apoptin is a powerful apoptosis-inducing protein with a potential for cancer therapy.

Molecular markers in oral epithelial dysplasia: review

The clinical and histologic features alone cannot accurately predict whether potentially malignant disorders of the oral mucosa remain stable, regress or progress to malignancy. Some of them, with or without epithelial dysplasia, may transform to invasive oral squamous cell carcinomas (OSCC). Identification of molecular markers which can predict disease progression is necessary to improve the management of these disorders. Many genes and signaling pathways have been shown to be involved in the development of OSCC. This review summarizes some molecular markers researched in the detection of pre-cancer. We highlight selected markers that are reported to be significantly associated with progression of potentially malignant disorders to OSCC. These include alterations in genes/pathways which control cellular signaling, cell cycle, apoptosis, genomic stability, cytoskeleton, angiogenesis, etc. However, these genetic tumor markers have so far not gained any use in routine diagnosis and their utility in the prediction of risk of malignant transformation remains unknown. It is, however, clear from the large number of studies, some described in this review, that multiple genes/pathways are involved in the progression from normal to metaplastic/dysplastic, and subsequently to cancer. It is therefore necessary to study those significant alterations in multiple genes simultaneously in biopsy samples from large cohorts of subjects.

Role of p16/MTS1, cyclin D1 and RB in primary oral cancer and oral cancer cell lines.

One of the most important components of G1 checkpoint is the retinoblastoma protein (pRB110). The activity of pRB is regulated by its phosphorylation, which is mediated by genes such as cyclin D1 and p16/MTS1. All three genes have been shown to be commonly altered in human malignancies. We have screened a panel of 26 oral squamous cell carcinomas (OSCC), nine premalignant and three normal oral tissue samples as well as eight established OSCC cell lines for mutations in the p16/MTS1 gene. The expression of p16/MTS1, cyclin D1 and pRB110 was also studied in the same panel. We have found p16/MTS1 gene alterations in 5/26 (19%) primary tumours and 6/8 (75%) cell lines. Two primary tumours and five OSCC cell lines had p16/MTS1 point mutations and another three primary and one OSCC cell line contained partial gene deletions. Six of seven p16/MTS1 point mutations resulted in termination codons and the remaining mutation caused a frameshift. Western blot analysis showed absence of p16/MTS1 expression in 18/26 (69%) OSCC, 7/9 (78%) premalignant lesions and 8/8 cell lines. One cell line, H314, contained a frameshift mutation possibly resulting in a truncated p16/MTS1 protein. pRB was detected in 14/25 (56%) of OSCC but only 11/14 (78%) of these contained all or some hypophosphorylated (active) pRB. In premalignant samples, 6/8 (75%) displayed pRB, and all three normal samples and eight cell lines analysed contained RB protein. p16/MTS1 protein was undetectable in 10/11 (91%) OSCCs with positive pRB. Overexpression of cyclin D1 was observed in 9/22 (41%) OSCC, 3/9 (33%) premalignant and 8/8 (100%) of OSCC cell lines. Our data suggest p16/MTS1 mutations and loss of expression to be very common in oral cancer cell lines and less frequent in primary OSCC tumours. A different pattern of p16/MTS1 mutations was observed in OSCC compared to other cancers with all the detected p16/MTS1 mutations resulting in premature termination codons or a frameshift. The RB protein was expressed in about half (44%) of OSCCs and its expression inversely correlated with p16/MTS1 expression. In conclusion, we show that abnormalities of the RB pathway are a common mechanism of oral carcinogenesis.

p53 is upregulated in Alzheimer's disease and induces tau phosphorylation in HEK293a cells

p53 and tau are both associated with neurodegenerative disorders. Here, we show by Western blotting that p53 is upregulated approximately 2-fold in the superior temporal gyrus of Alzheimers patients compared to healthy elderly control subjects. Moreover, p53 was found to induce phosphorylation of human 2N4R tau at the tau-1/AT8 epitope in HEK293a cells. Confocal microscopy revealed that tau and p53 were spatially separated intracellularly. Tau was found in the cytoskeletal compartment, whilst p53 was located in the nucleus, indicating that the effects of p53 on tau phosphorylation are indirect. Collectively, these findings have ramifications for neuronal death associated with Alzheimers disease and other tauopathies.

Clinical update on cancer: molecular oncology of head and neck cancer

Head and neck cancers encompass a heterogeneous group of tumours that, in general, are biologically aggressive in nature. These cancers remain difficult to treat and treatment can cause severe, long-term side effects. For patients who are not cured by surgery and/or (chemo)radiotherapy, there are few effective treatment options. Targeted therapies and predictive biomarkers are urgently needed in order to improve the management and minimise the treatment toxicity, and to allow selection of patients who are likely to benefit from both nonselective and targeted therapies. This clinical update aims to provide an insight into the current understanding of the molecular pathogenesis of the disease, and explores the novel therapies under development and in clinical trials.

Prevalence of human papillomavirus infection in premalignant and malignant lesions of the oral cavity in U.K. subjects : a novel method of detection

To evaluate the possible role of human papillomavirus (HPV) in oral neoplasms, 28 oral squamous cell carcinomas (SCC) and 12 potentially malignant lesions were analysed for the presence of HPV DNA. A nested polymerase chain reaction (PCR) approach, using two sets of HPV consensus primers to the L1 region, was used, which was able to detect a broad spectrum of HPV types. HPV DNA was detected in 14/28 (50%) carcinomas and 4/12 (33%) precancerous lesions. A novel approach based on labelling the PCR products with 32P and the separation of radioactively labelled products on an 8% polyacrylamide gel increased the sensitivity of the detection and enabled the identification of the HPV types. The typing of HPV was subsequently confirmed by direct DNA sequencing. HPV 6 and HPV 16 were the only HPV types detected and seven tumours harboured both types. Our results suggest that HPVs may be an important aetiological factor in the development of oral cancer. The detection procedure ensured sensitivity and consistency of the detection of low copy numbers of the virus DNA. The presence of HPV in 33% of premalignant tissues suggests that HPV infection may be an early event in the malignant transformation of oral SCC. There was no statistically significant association between viral infection and tumour grade or stage.

Acid ceramidase inhibition: a novel target for cancer therapy

During the last decade, sphingolipid deregulation, namely the balance between the pro-apoptotic molecule ceramide and the anti-apoptotic sphingolipid sphingosine-1-phosphate, has emerged as an important factor in cancer pathology and resistance to therapy. Thus, our research has been focused on developing drugs that are able to restore normal sphingolipid balance, precisely through increasing the levels of ceramide and decreasing sphingosine-1-phosphate. Particularly, inhibition of the ceramide metabolizing enzyme acid ceramidase, whose over-expression in cancer cells has been implicated in resistance to treatment, is proving to be an efficient and promising strategy. In this review, we consider our recent work with acid ceramidase inhibitors, in combination with radiation or gene therapy as a sensitizer that enhance cancer therapy.

Combined therapeutic use of AdGFPFasL and small molecule inhibitors of ceramide metabolism in prostate and head and neck cancers: a status report.

As of January 2005, there were 1020 gene therapy clinical trials ongoing worldwide with 675 or 66.2% devoted to cancer gene therapy. The majority are occurring in the US and Europe (http://www.wiley.co.uk/genetherapy/clinical/). At the present time, to our knowledge there are no trials that employ gene delivery of Fas Ligand (FasL). As an important note, and in contrast to somatic cell therapy trials, there are no reported deaths due to therapeutic vector administration in any cancer gene therapy trial. That said, from our studies and from the published literature, the issue of gene delivery remains the major obstacle to successfully employing gene therapy for cancer treatment. Numerous laboratories are studying this with many different approaches. My co-workers and I have focused on the delivery issue by using various approaches that address tumor targeting and transgene expression. In addition, we are focusing on enhancing tumor cell killing via the bystander effect and through use of small molecules to enhance bystander activity.

Expression of p53 in oral squamous cell carcinoma is associated with the presence of IgG and IgA p53 autoantibodies in sera and saliva of the patients.

Around 50% of head and neck cancers are known to have aberrations of the p53 gene. Overexpression of the mutant p53 protein can induce a specific humoral response in cancer patients. Matched saliva, serum, and tissue samples from 26 patients with histologically confirmed oral squamous and verrucous carcinoma were investigated. p53 protein expression was evaluated by immunohistochemistry and antibodies specific for 53 protein were analysed in sera and whole mouth saliva by ELISA, immunoprecipitation, and competition assays; 16/25 (64%) samples demonstrated the stabilized p53 protein in tissues and 7/26 (27%) had a high level of p53 antibody in serum. In samples where matching saliva was available, p53 antibody was also present in saliva. In some tumours, only IgA‐type p53 antibody was detected. p53 antibodies were found only in the serum and saliva of patients who showed p53 overexpression in their tumour tissues. These results demonstrate that detection of p53 antibodies can offer a specific and non‐invasive method for the detection of a subset of tumours with p53 aberrations. Copyright