Background: In order to improve therapy for HNSCC patients, novel methods to predict and combat local and/or distant tumour relapses are urgently needed. This study has been dedicated to the hypothesis that Rac1, a Rho GTPase, is implicated in HNSCC insensitivity to chemo-radiotherapy resulting in tumour recurrence development.Methods: Parental and radiation-resistant (IRR) HNSCC cells were used to support this hypothesis. All cells were investigated for their sensitivity to ionising radiation and cisplatin, Rac1 activity, its intracellular expression and subcellular localisation. Additionally, tumour tissues obtained from 60 HNSCC patients showing different therapy response were evaluated for intratumoral Rac1 expression.Results: Radiation-resistant IRR cells also revealed resistance to cisplatin accompanied by increased expression, activity and trend towards nuclear translocation of Rac1 protein. Chemical inhibition of Rac1 expression and activity resulted in significant improvement of HNSCC sensitivity to ionising radiation and cisplatin. Preclinical results were confirmed in clinical samples. Although Rac1 was poorly presented in normal mucosa, tumour tissues revealed increased Rac1 expression. The most pronounced Rac1 presence was observed in HNSCC patients with poor early or late responses to chemo-radiotherapy. Tissues taken at recurrence were characterised not only by enhanced Rac1 expression but also increased nuclear Rac1 content.Conclusions: Increased expression, activity and subcellular localisation of Rac1 could be associated with lower early response rate and higher risk of tumour recurrences in HNSCC patients and warrants further validation in larger independent studies. Inhibition of Rac1 activity can be useful in overcoming treatment resistance and could be proposed for HNSCC patients with primary or secondary chemo-radioresistance.

In contrast to primary hepatocytes, estimating carrier-mediated hepatic disposition by using a panel of single transfected cell-lines provides direct information on the contribution of the individual transporters to the net disposition. The most direct way to correct for differences in transporter abundance between cell-lines and tissue is by using absolute protein quantification. In the present study, the performance of this strategy to predict human hepatic uptake transport was investigated and compared with traditional scaling from primary human hepatocytes. Rosuvastatin was used as a model compound. The uptake activity was measured in HEK293 cell-lines stably overexpressing OATP1B1∗1a, OATP1B3 or OATP2B1, the major transporters involved in human hepatic uptake of rosuvastatin, or expressing OATP1B1∗15, associated with reduced hepatic uptake of rosuvastatin. The abundance of these transporter proteins in the outer membranes of HEK293-cells, in human primary hepatocytes and in human liver tissue was determined by LC–MS/MS. The measured activity, corrected for protein abundance and scaled to the whole liver, gave a very accurate prediction of the hepatic intrinsic clearance observed in vivo. Embedded in a PBPK model describing the hepatic disposition and enterohepatic circulation, the collective in vitro data resulted in a good explanation of the observed oral and intravenous pharmacokinetic profiles of rosuvastatin. The model allowed simulation of the effect of polymorphic variants of OATP1B1 on rosuvastatin pharmacokinetics. These results encourage a larger scale validation. This approach may facilitate prediction of drug–drug interactions, scaling of transporter processes across subpopulations (children, diseased patients), and may be extended to tissues for which primary cells may be more difficult to obtain.

We present the current state-of-the art of computer-assisted interstitial (fractionated) brachytherapy as a “picture-book” without wanting to give an in-depth presentation of either brachytherapy itself or of otolaryngologic aspects of oncologic treatment. However, our results show that 3D-computer-assisled navigation techniques can successfully be applied in interstitial brachytherapy to exactly plan the hollow-needle’s position(s) in order to reach a prospective planning of brachytherapy which exploits the full 3D-information of the modern imagery and incorporates state-of-the-art navigational techniques.