Transketolase-like protein 1 confers resistance to serum withdrawal in vitro.

Transketolase-like protein 1 (TKTL1) is a member of the family of transketolase enzymes of which the founder member transketolase (TKT) is known to play a central role in the non-oxidative part of the pentose phosphate pathway. According to several publications TKTL1 is the only family member, whose expression is substantially de-regulated in a variety of solid tumours. Over-expression of TKTL1 correlates with poor prognosis of cancer patients and TKTL1 itself represents a potential therapeutic target owing to its possible involvement in the regulation of the proliferation and metabolism of cancer cells. We show that exogenously expressed TKTL1 provides HEK293 cells with moderate growth advantages under standard culture conditions, while protecting cells from growth factor withdrawal-induced apoptosis. Importantly, we identified TKTL1 with the JFC12T10 antibody as a 65kDa protein, which was however absent in most tumour cell lines tested. Primary head and neck squamous cell carcinomas of various localisations were characterised by a focal pattern with single cells strongly expressing TKTL1, rather than by a homogeneous expression pattern within the tumour mass

Confocal laser endomicroscopy in head and neck malignancies using FITC-labelled EpCAM- and EGF-R-antibodies in cell lines and tumor biopsies.

Intraoperative detection of residual malignant cells at tumor margins following excision of primary tumors could help improving surgery and thus patients' outcome. The feasibility of the tumor antigens epidermal growth factor receptor (EGF-R) and epithelial cell adhesion molecule (EpCAM) for antibody-dependent confocal laser scanning endomicroscopy (CLE)-mediated visualization of malignant cells was addressed. Both tumor antigens are highly and frequently expressed in the majority of carcinomas, including head and neck squamous cell carcinomas (HNSCC), and represent prognostic and therapeutic tumor target molecules. FITC-conjugated EGF-R- and EpCAM-specific antibodies served as molecular tools for the detection of antigen-positive cells using the CLE technology. Specificity of both antibodies and their ability to discriminate tumor from non-tumor cells were assessed in vitro with human fibroblasts and PCI-1 HNSCC cell lines, and ex vivo on primary HNSCC samples (n = 11) and healthy mucosa (n = 5). Antigen specificity of the used EpCAM-specific antibody was superior to that of the EGF-R-specific antibody both in vitro and ex vivo (100% vs. 31.25%), and allowed visualization of cellular structures in CLE measurements. These results hold promise for possible future applications in humans