title: Reactivating p53 and Inducing Tumor Apoptosis (RITA) Enhances the Response of RITA-Sensitive Colorectal Cancer Cells to Chemotherapeutic Agents 5-Fluorouracil and Oxaliplatin.
abstract: Colorectal carcinoma (CRC) is the most common cancer of the gastrointestinal tract with frequently dysregulated intracellular signaling pathways, including p53 signaling. The mainstay of chemotherapy treatment of CRC is 5-fluorouracil (5FU) and oxaliplatin. The two anticancer drugs mediate their therapeutic effect via DNA damage-triggered signaling. The small molecule reactivating p53 and inducing tumor apoptosis (RITA) is described as an activator of wild-type and reactivator of mutant p53 function, resulting in elevated levels of p53 protein, cell growth arrest, and cell death. Additionally, it has been shown that RITA can induce DNA damage signaling. It is expected that the therapeutic benefits of 5FU and oxaliplatin can be increased by enhancing DNA damage signaling pathways. Therefore, we highlighted the antiproliferative response of RITA alone and in combination with 5FU or oxaliplatin in human CRC cells. A panel of long-term established CRC cell lines (n=9) including p53 wild-type, p53 mutant, and p53 null and primary patient-derived, low-passage cell lines (n=5) with different p53 protein status were used for this study. A substantial number of CRC cells with pronounced sensitivity to RITA (IC50<3.0 μmol/l) were identified within established (4/9) and primary patient-derived (2/5) CRC cell lines harboring wild-type or mutant p53 protein. Sensitivity to RITA appeared independent of p53 status and was associated with an increase in antiproliferative response to 5FU and oxaliplatin, a transcriptional increase of p53 targets p21 and NOXA, and a decrease in MYC mRNA. The effect of RITA as an inducer of DNA damage was shown by a strong elevation of phosphorylated histone variant H2A.X, which was restricted to RITA-sensitive cells. Our data underline the primary effect of RITA, inducing DNA damage, and demonstrate the differential antiproliferative effect of RITA to CRC cells independent of p53 protein status. We found a substantial number of RITA-sensitive CRC cells within both panels of established CRC cell lines and primary patient-derived CRC cell lines (6/14) that provide a rationale for combining RITA with 5FU or oxaliplatin to enhance the antiproliferative response to both chemotherapeutic agents.
authors.affiliation: Department of General, Visceral, Vascular and Pediatric Surgery, University Hospital of Würzburg, Oberdürrbacher Str. 6, D-97080, Würzburg, Germany; Department of Biochemistry and Molecular Biology, Theodor-Boveri-Institute, Biocenter, University of Würzburg, D-97070 Würzburg, Germany. Electronic address: wiegering_a@ukw.de.
authors.forename: Armin
authors.initials: A
authors.lastname: Wiegering
authors.affiliation: Department of General, Visceral, Vascular and Pediatric Surgery, University Hospital of Würzburg, Oberdürrbacher Str. 6, D-97080, Würzburg, Germany. Electronic address: Matthes_N@ukw.de.
authors.forename: Niels
authors.initials: N
authors.lastname: Matthes
authors.affiliation: Experimental Surgery, Department of General, Visceral, Vascular, and Pediatric Surgery, University Hospital of Würzburg, Oberdürrbacher Str. 6, D-97080 Würzburg, Germany. Electronic address: Muehling_B@ukw.de.
authors.forename: Bettina
authors.initials: B
authors.lastname: Mühling
authors.affiliation: Experimental Surgery, Department of General, Visceral, Vascular, and Pediatric Surgery, University Hospital of Würzburg, Oberdürrbacher Str. 6, D-97080 Würzburg, Germany. Electronic address: Koospal_M@ukw.de.
authors.forename: Monika
authors.initials: M
authors.lastname: Koospal
authors.affiliation: Experimental Surgery, Department of General, Visceral, Vascular, and Pediatric Surgery, University Hospital of Würzburg, Oberdürrbacher Str. 6, D-97080 Würzburg, Germany. Electronic address: Anne.Quenzer@hotmail.com.
authors.forename: Anne
authors.initials: A
authors.lastname: Quenzer
authors.affiliation: Department of Biochemistry and Molecular Biology, Theodor-Boveri-Institute, Biocenter, University of Würzburg, D-97070 Würzburg, Germany. Electronic address: peter_s@ukw.de.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Peter
authors.affiliation: Department of General, Visceral, Vascular and Pediatric Surgery, University Hospital of Würzburg, Oberdürrbacher Str. 6, D-97080, Würzburg, Germany. Electronic address: Germer_C@ukw.de.
authors.forename: Christoph-Thomas
authors.initials: CT
authors.lastname: Germer
authors.affiliation: Molecular Oncology and Immunotherapy, Department of General, Thoracic, Vascular and Transplantation Surgery, University of Rostock, Schillingallee 35, D-18055 Rostock, Germany. Electronic address: Michael.Linnebacher@med.uni-rostock.de.
authors.forename: Michael
authors.initials: M
authors.lastname: Linnebacher
authors.affiliation: Department of General, Visceral, Vascular and Pediatric Surgery, University Hospital of Würzburg, Oberdürrbacher Str. 6, D-97080, Würzburg, Germany; Experimental Surgery, Department of General, Visceral, Vascular, and Pediatric Surgery, University Hospital of Würzburg, Oberdürrbacher Str. 6, D-97080 Würzburg, Germany. Electronic address: Otto_c@ukw.de.
authors.forename: Christoph
authors.initials: C
authors.lastname: Otto
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics*; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000378:metabolism; D004249:DNA Damage; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D005472:Fluorouracil / Q000494:pharmacology*; D015870:Gene Expression; D006801:Humans; D009154:Mutation; D009944:Organoplatinum Compounds / Q000494:pharmacology*; D000077150:Oxaliplatin; D015398:Signal Transduction / Q000187:drug effects; D016159:Tumor Suppressor Protein p53 / Q000235:genetics*
chemical_list: D000970:Antineoplastic Agents; D009944:Organoplatinum Compounds; D016159:Tumor Suppressor Protein p53; D000077150:Oxaliplatin; D005472:Fluorouracil