Lack of microvessels in well-differentiated regions of human head and neck squamous cell carcinoma A253 associated with functional magnetic resonance imaging detectable hypoxia, limited drug delivery, and resistance to irinotecan therapy.
OBJECTIVE
Combination chemotherapy with irinotecan (CPT-11; 50 mg/kg/week x 4 intravenously), followed 24 hour later by 5-fluorouracil (50 mg/kg/week x 4 intravenously), results in 10 and 100% cure rates of animals bearing human head and neck squamous cell carcinoma xenografts A253 and FaDu, respectively. A253 consists of 30% well-differentiated and avascular and 70% poorly differentiated regions with low microvessel density (10/x400), whereas FaDu is uniformly poorly differentiated with higher microvessel density (19/x400). Studies were carried out for determining the role of well-differentiated and avascular regions in drug resistance in A253 and detection of such regions with noninvasive functional magnetic resonance (fMR) imaging.


METHODS
Tumors were harvested for histopathologic evaluation and immunohistochemistry (CD31, CD34; differentiation marker: involucrin; hypoxia markers: carbonic anhydrase IX, pimonidazole; vascular endothelial factor (VEGF) and Ki67) immediately after fMR imaging following the 3rd dose of chemotherapy. High-performance liquid chromatography determination of intratumoral drug concentration of 7-ethyl-10-hydroxyl-camptothecin and autoradiography with (14)C-labeled CPT-11 was done 2 hours after CPT-11 administration.


RESULTS
Although A253 xenografts showed three times higher concentration of 7-ethyl-10-hydroxyl-camptothecin, FaDu was more responsive to therapy. After therapy, A253 tumor consisted mostly (approximately 80%) of well-differentiated regions (positive for involucrin) lacking microvessels with a hypoxic rim (positive for carbonic anhydrase IX and pimonidazole) containing few proliferating (Ki67 positive) poorly differentiated cells. Autoradiography revealed that well-differentiated A253 tumor regions showed 5-fold lower (14)C-labeled CPT-11 concentrations compared with poorly differentiated areas (P < 0.001). Blood oxygen level dependant fMR imaging was able to noninvasively distinguish the hypoxic and well-vascularized regions within the tumors.


CONCLUSIONS
Avascular-differentiated regions in squamous cell carcinoma offer sanctuary to some hypoxic but viable tumor cells (carbonic anhydrase IX and Ki67 positive) that escape therapy because of limited drug delivery. This study provides direct evidence that because of a specific histologic structure, avascular, well-differentiated hypoxic regions in tumors exhibit low drug uptake and represent a unique form of drug resistance.
Bhattacharya
Arup
A
Department of Cancer Biology, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, NY 14263, USA.
Tóth
Károly
K
Mazurchuk
Richard
R
Spernyak
Joseph A
JA
Slocum
Harry K
HK
Pendyala
Lakshmi
L
Azrak
Rami
R
Cao
Shousong
S
Durrani
Farukh A
FA
Rustum
Youcef M
YM
D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D014408:Biomarkers, Tumor / Q000378:metabolism; D002166:Camptothecin / Q000008:administration & dosage / Q000031:analogs & derivatives*; D002294:Carcinoma, Squamous Cell / Q000098:blood supply / Q000188:drug therapy* / Q000532:radiotherapy; D002454:Cell Differentiation; D016503:Drug Delivery Systems; D019008:Drug Resistance, Neoplasm; D005260:Female; D005472:Fluorouracil / Q000008:administration & dosage; D006258:Head and Neck Neoplasms / Q000098:blood supply / Q000188:drug therapy* / Q000532:radiotherapy; D006801:Humans; D000860:Hypoxia; D000077146:Irinotecan; D008279:Magnetic Resonance Imaging; D051379:Mice; D008819:Mice, Nude; D008833:Microcirculation; D010100:Oxygen / Q000097:blood; D051381:Rats; D014183:Transplantation, Heterologous; D014407:Tumor Cells, Cultured
D014408:Biomarkers, Tumor; D000077146:Irinotecan; D010100:Oxygen; D005472:Fluorouracil; D002166:Camptothecin