Nucleotide sequence analysis of c-raf-1 cDNA and promoter from a radiation-resistant human squamous carcinoma cell line: deletion within exon 17

Selective Raf inhibition in cancer therapy

Over the past 5 years, the Raf kinase family has emerged as a promising target for protein-directed cancer therapy development. The goal of this review is to first provide a concise summary of the data validating Raf proteins as high-interest therapeutic targets. The authors then outline the mode of action of Raf kinases, emphasizing how Raf activities and protein interactions suggest specific approaches to inhibiting Raf. The authors then summarize the set of drugs, antisense reagents and antibodies available or in development for therapeutically targeting Raf or Raf-related proteins, as well as existing strategies combining these and other therapeutic agents. Finally, the authors discuss recent results from systems biology analyses that have the potential to increasingly guide the intelligent selection of combination therapies involving Raf-targeting agents and other therapeutics.

Kinase inhibitors in cancer therapy: a look ahead

The most essential kinases involved in cell membrane receptor activation, signal transduction and cell cycle control or programmed cell death and their interconnections are reviewed. In tumours, the genes of many of those kinases are mutated or amplified or the proteins are overexpressed. The use of key kinases offers the possibility to screen in vitro for synthetic small molecule kinase inhibitors. In view of the many interconnections of cellular kinases, their role in preventing or inducing programmed cell death and the possibility that a considerable number of signal transducing proteins are still unknown, cellular test systems are recommended in which the respective key kinase or one of its main partner molecules are overexpressed.

Identification of seven differentially displayed transcripts in human primary and matched metastatic head and neck squamous cell carcinoma cell lines: implications in metastasis and/or radiation response

The patterns of differential gene expression were examined in two primary (A's) and two matched-metastatic (B's) head and neck squamous cell carcinoma (HNSCC) cell lines by differential display of mRNAs and northern blot hybridisation. Three cell lines used (PCI-04A, PCI-04B and PCI-06A) were established independently prior to therapy, whereas one cell line (PCI-06B) was established from a recurrent tumor after radiation therapy. A total of seven differentially displayed mRNA clones were identified, of which six clones were obtained by comparison of PCI-06A cells with PCI-06B cells (SCC-S1a/b, SCC-1c, and SCC-S2, PCI-06B; SCC-S3 to SCC-S5, PCI-06A), and one clone was obtained from the PCI-04A and PCI-04B match (SCC-Sa, PCI-04B). Based on the DNA database search for homology to the known sequences, six of the seven partial cDNA clones (SCC-S1a/b, SCC-1c, SCC-S2 to SCC-S4, and SCC-Sa may represent novel genes, whereas one cDNA clone (SCC-S5) shows significant homology to the HLA class II antigen gene (DPW2 beta chain). Each of the seven clones revealed preferential expression by northern blotting in the cell line of origin as compared to the matched counterpart. The transcripts ranged in size from approximately 7.0 Kb to 0.5 Kb. Interestingly, the SCC-Sa clone was preferentially expressed in both metastatic cell lines compared to the primary tumour-derived cell lines. We conclude that the SCC-Sa gene may be more commonly involved in tumour metastasis, whereas expression of the other genes (SCC-S1a/b, SCC-S1c, SCC-S2-SCC-S5) may be associated with metastasis and/or response of HNSCC to ionising radiation.

Cell, tissue and organ culture as in vitro models to study the biology of squamous cell carcinomas of the head and neck

In vitro models are currently being used to study head and neck squamous cell carcinoma (HNSCC). Several hundred HNSCC cell lines have been established by various investigators and used to study a broad spectrum of questions related to head and neck cancer. The head and neck model with respect to multistage carcinogenesis is now complete. Several techniques exist for the culture of normal epithelial cells from the upper aerodigestive tract (UADT). The biology of these UADT cells (oral cavity, oropharynx, hypopharynx and larynx) is being studied. Successful culture of premalignant lesions (dysplastic mucosa, leukoplakia, erythroplakia) has resulted in establishment of a limited number of premalignant cell lines and cell cultures. HPV infection of normal oral epithelial cells for immortalization (approximately premalignant cells) coupled with transformation with carcinogens (malignant cells) has established an experimental model for progression. Two in vivo models for oral carcinogenesis, the 7,12 dimethylbenz(a)anthracene-induced hamster cheek pouch model and the 4-nitroquinoline-N-oxide rat oral model, have been established in culture. Thus, multistage carcinogenesis models have been established from both human tissues and animal models and include cultures of normal, premalignant and malignant cells. Culture techniques for growing dissociated primary tumor cells for short term experimental analysis are being used. The culture of normal or tumor tissue as organ/explant cultures allows for the maintenance of normal cell-cell and cell-matrix interaction, but limits experimentation since these cultures cannot be propagated. Several three dimensional model systems are being used to obtain this histological complexity but allow for experimentation. The ability to culture normal, premalignant and malignant cells coupled with the use of a variety of culture techniques, should allow for the continued growth and experimentation in head and neck cancer research.

Biological staging of head and neck cancer and its role in developing effective treatment strategies

The purpose of a cancer staging system is to encompass all attributes of a tumor that define its life history. We propose a biological staging system which incorporates all of the phases of the natural history of head and neck cancer beginning with the earliest cellular changes extending through the early phase of invasion to the occurrence of metastasis and, finally, culminating in therapeutically refractory disease. This temporally structured system recognizes the importance of constitutional predisposition, and the impact of environmental factors. The intent is to augment the AJCC/UICC staging system and use this system to provide a framework which will easily incorporate current and future advances in basic science, prevention, therapy and palliation which will improve the quality and quantity of life for patients.