title: Hypoxia-specific drug tirapazamine does not abrogate hypoxic tumor cells in combination therapy with irinotecan and methylselenocysteine in well-differentiated human head and neck squamous cell carcinoma a253 xenografts.
abstract: Well-differentiated hypoxic regions in head and neck squamous cell carcinoma like in A253 xenografts are avascular and, therefore, hinder drug delivery leading to drug resistance and tumor regrowth. Methylselenocysteine (MSC, 0.2 mg/mouse per day per oral for 35 days starting 7 days before the first irinotecan (CPT-11)) has been found to increase efficacy of a wide variety of chemotherapeutic agents including CPT-11 (100 mg/kg per week x 4 intravenously). Whereas CPT-11 leads to a 10% complete response (CR) in A253 xenografts, the combination of MSC and CPT-11 increased the CR to 70%. Surviving tumors were found to consist largely of avascular hypoxic regions. Here, we investigated the combination of tirapazamine (TPZ, 70 mg/kg per week intraperitoneal x 4 administered 3 or 72 hours before CPT-11), a bioreductive drug in clinical trial with selective toxicity for hypoxic cells, with MSC and CPT-11 in further enhancing the cure rates. Tumor response, change in tumor hypoxic regions, and DNA damage were monitored in vivo. Tirapazamine administered 3 hours before CPT-11 in combination with MSC + CPT-11 led to a lower tumor burden. Tirapazamine did not increase cure rate beyond that of MSC + CPT-11 combination and was instead found to decrease cures with no evidence of an increased DNA damage or a significant reduction in avascular hypoxic tumor regions. CD31 immunostaining in A253 demonstrated disruption of tumor vessels by TPZ that could lower cytotoxic drug delivery to carbonic anhydrase IX-positive hypoxic tumor cells and may explain at least partially these unexpected results.
authors.affiliation: Department of Cancer Biology, Roswell Park Cancer Institute, Buffalo, NY 14263, USA. Arup.Bhattacharya@Roswellpark.org
authors.forename: Arup
authors.initials: A
authors.lastname: Bhattacharya
authors.forename: Károly
authors.initials: K
authors.lastname: Tóth
authors.forename: Farukh A
authors.initials: FA
authors.lastname: Durrani
authors.forename: Shousong
authors.initials: S
authors.lastname: Cao
authors.forename: Harry K
authors.initials: HK
authors.lastname: Slocum
authors.forename: Sreenivasulu
authors.initials: S
authors.lastname: Chintala
authors.forename: Youcef M
authors.initials: YM
authors.lastname: Rustum
mesh_terms: D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000008:administration & dosage* / Q000494:pharmacology; D002166:Camptothecin / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy* / Q000473:pathology; D002454:Cell Differentiation / Q000187:drug effects; D015687:Cell Hypoxia; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D003545:Cysteine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D005260:Female; D051858:Forkhead Transcription Factors / Q000172:deficiency; D006258:Head and Neck Neoplasms / Q000188:drug therapy* / Q000473:pathology; D006801:Humans; D000077146:Irinotecan; D020714:Maximum Tolerated Dose; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D016566:Organoselenium Compounds / Q000008:administration & dosage* / Q000494:pharmacology; D017279:Selenocysteine / Q000031:analogs & derivatives; D000077704:Tirapazamine; D014227:Triazines / Q000008:administration & dosage / Q000494:pharmacology; D023041:Xenograft Model Antitumor Assays
chemical_list: D051858:Forkhead Transcription Factors; D016566:Organoselenium Compounds; D014227:Triazines; D017279:Selenocysteine; D000077704:Tirapazamine; D000077146:Irinotecan; D003545:Cysteine; C002979:selenomethylselenocysteine; D002166:Camptothecin