Preclinical studies on suicide gene therapy for head/neck cancer: a novel method for evaluation of treatment efficacy.

BACKGROUND: Malignancies of the oral cavity and oropharynx account for 31% of all diagnosed cancers in India. In most cases, patients present with tumours that are clinically stage III/IV where surgery, radiotherapy and chemotherapy have not been very effective. Hence, there is an urgent need for alternate treatment modalities. Gene therapy is a recent development shown to be effective in various malignancies. In this study we have attempted to cause bulk reduction in tumour volume using the HSVtk/ganciclovir strategy, solely on the basis of the 'bystander' effect. METHODS: Nude mouse xenograft tumours of human head/neck cancer were engrafted with cells expressing viral thymidine kinase. After treatment with 8 mM ganciclovir for 14 days, the treatment efficacy was monitored. A novel method has been devised to evaluate cell kill microscopically in the whole tumour. RESULTS: Of the 11 mice included in the study, 9 showed a significant reduction in total tumour volume of treated versus control tumours (p = 0.015). CONCLUSIONS: Bulk reduction in tumour load can be brought about without use of viral vectors for gene transfer solely by the bystander effect.

Establishment of a human squamous cell carcinoma cell line of the upper aero-digestive tract.

A human squamous cell carcinoma (SCC) cell line has been established from the surgical specimen of an untreated, upper aero-digestive tract tumour, diagnosed as a squamous carcinoma, grade III, of the pyriform fossa. The tumour tissue was grown as a xenograft in an athymic nude mouse and was designated as NT-8. Histological examination of the surgical specimen and the nude mouse tumour showed that the two were identical. NT-8 was subsequently passed by subcutaneous injections into nude mice. After the 6th passage in nude mouse, the tumour was cultured in vitro where it grew as an epithelial cell line, with a typical cobblestone appearance. This cell line was designated as NT-8e. Both the primary tumour as well as xenograft and the cells in culture have retained several common morphological and biochemical characteristics. Immunological markers for epithelial cells including epithelial membrane antigen and cytokeratins were seen in all three, confirming the epithelial lineage. Characterization of the NT-8e cell line including growth parameters, anchorage-independent growth and tumorigenicity in nude mice, chromosome counts and DNA content by flow cytometry have been carried out.

Enhancing factor, a Paneth cell specific protein from mouse small intestines: predicted amino acid sequence from RT-PCR amplified cDNA and its expression.

Enhancing factor (EF), a Paneth cell specific growth factor modulator, has been identified in our laboratory from mouse small intestines. In this paper we describe generation of an EF specific cDNA by RT-PCR and its sequence. The predicted amino acid sequence was found to be similar to, and hence confirms, the partial amino acid sequence obtained earlier by protein sequencing. In Northern blot analysis, a 1 kb transcript was observed in intestinal RNA alone. In situ hybridization indicated that the EF gene is expressed exclusively in the Paneth cells. The present study indicates that EF is an isoform of PLA2 type II, with a unique tissue distribution, found predominantly in the Paneth cells of the small intestines. Further, based on the properties of EF, we propose that isoforms of PLA2, belonging to type II, may be involved in regulation of cell proliferation via EGF binding.

Sonographic diagnosis of a splenic artery pseudoaneurysm incorporated within an infected pancreatic pseudocyst.

In pancreatitis the involvement of adjacent vessels resulting in pseudoaneurysm formation is well known, though quite rare (Gadacz 1978, Kadell & Riley 1967). The diagnosis is usually established on angiography or surgery. We report here a case where the diagnosis of a splenic artery pseudoaneurysm incorporated within an infected pseudocyst, was made sonographically.

Expression of enhancing factor gene and its localization in mouse tissues.

Enhancing factor (EF), a 14 kDa protein, isolated from mouse small intestines, has been reported from this laboratory. Based on our earlier studies EF has been implicated in cell proliferation. Preliminary immunohistochemical studies have shown EF to be localized in the Paneth cells of small intestines. In this paper we report the tissue distribution of EF using conditions optimized for immunohistochemical staining. In addition, the data are supported by northern blot analysis using a nick translated cDNA probe specific for EF. The results indicate that EF gene is actively transcribed mainly in the intestines. The chief source of synthesis of EF appears to be the Paneth cells located at the base of the crypts of Lieberkühn.

Ontogeny of enhancing factor in mouse intestines and skin.

Enhancing Factor (EF) is a 14 kDa protein isolated from mouse small intestines, which enhances the binding of 125I-EGF to A431 cells. This observation as well as our earlier in vitro studies have indicated that EF is a modulator of EGF. In adult mice, localization of EF by immunohistochemistry shows it is present predominantly in the Paneth cells of the small intestines and to a lesser extent in the stomach and colon. This study of the ontogeny of EF shows that the appearance of the protein coincides with the appearance of mature Paneth cells. In new born mouse skin EF is localized in the hair follicles in the first hair cycle from day 2 to day 8. It is however absent in the adult skin. Thus EF is associated with tissues which have a high growth rate.