molecularly targeted compound with radiotherapy. Within this context, i.e., that the possible mechanism of radiosensitizing action of the molecularly targeted agent should be regarded a main objective in a combined-modality study with radiotherapy, the present study reports on a correlative analytical strategy for identifying possible biomarkers of HDAC inhibitor activity, using peripheral blood mononuclear cells from the PRAVO phase 1 study patients receiving pelvic palliative radiotherapy as an easily accessible surrogate tissue for vorinostat exposure. Gene expression array analysis identified PBMC genes that from experimental models are known to be implicated in biological processes governed by HDAC inhibitors, and might be further developed as pharmacodynamic biomarkers of vorinostat activity in the setting of order 120964-45-6 fractionated radiotherapy. Both of the protocols for the PRAVO study and the phase 2, non-randomized study for patients with locally advanced rectal cancer given neoadjuvant chemoradiotherapy were approved by the Institutional Review Board and the Regional Committee for Medical and Health Research Ethics South-East Norway, and were performed in accordance with the Declaration of Helsinki. Written informed consent was required for participation. The patient population was enrolled between February 2007 and May 2009. The principal eligibility criterion was histologically confirmed pelvic carcinoma scheduled to receive palliative radiation to 30 Gy in 3-Gy daily fractions. Other details on eligibility are given in the initial report. This phase 1 doseescalation study adopted a standard 3+3 expansion cohort design, where patients with advanced gastrointestinal carcinoma were enrolled onto four sequential dose levels of vorinostat, starting at 100 mg daily with dose escalation in increments of 100 mg. The primary objective was to determine tolerability of vorinostat, defined by TAK-875 dose-limiting toxicity and MTD, when administered concomitantly with palliative ra
