title: Rapid in vivo monitoring of chemotherapeutic response using weighted sodium magnetic resonance imaging.
abstract: A novel pulse sequence strategy uses sodium magnetic resonance imaging to monitor the response to chemotherapy of mouse xenograft tumors propagated from human prostate cancer cell lines. An inversion pulse suppresses sodium with long longitudinal relaxation times, weighting the image toward intracellular sodium nuclei. Comparing these weighted sodium images before and 24 h after administration of antineoplastics, we measured a 36 +/- 4% (P < 0.001; n = 16) increase in signal intensity. Experiments with these same drugs and cells, treated in culture, detected a significant intracellular sodium elevation (10-20 mM) using a ratiometric fluorescent dye. Flow cytometry studies showed that this elevation preceded cell death by apoptosis, as determined by fluorescent end-labeling of apoptotic nuclei or Annexin V binding. Histopathology on formalin-fixed sections of explanted tumors confirmed that drug administration reduces proliferation (2.2 versus 8.6 mitotic figures per high power field; P < 0.0001), an effect that inversely correlates with the sodium magnetic resonance image response on a tumor-to-tumor basis (P < 0.02; n = 10). Morphological features, such as central zones of nonviable cells, rims of active apoptosis, and areas of viable tumor, could be distinguished by comparing weighted and unweighted images. Advantages of this sodium imaging technique include rapid determination of drug efficacy, improved diagnosis of lesions, ease of coregistration with high resolution proton magnetic resonance imaging, and absence of costly or toxic reagents.
authors.affiliation: Department of Medicine, Columbia University, New York, New York 10032, USA. rpk1@Columbia.edu
authors.forename: R P
authors.initials: RP
authors.lastname: Kline
authors.forename: E X
authors.initials: EX
authors.lastname: Wu
authors.forename: D P
authors.initials: DP
authors.lastname: Petrylak
authors.forename: M
authors.initials: M
authors.lastname: Szabolcs
authors.forename: P O
authors.initials: PO
authors.lastname: Alderson
authors.forename: M L
authors.initials: ML
authors.lastname: Weisfeldt
authors.forename: P
authors.initials: P
authors.lastname: Cannon
authors.forename: J
authors.initials: J
authors.lastname: Katz
mesh_terms: D000818:Animals; D017304:Annexin A5 / Q000378:metabolism; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D017209:Apoptosis; D002467:Cell Nucleus / Q000378:metabolism; D000077143:Docetaxel; D005047:Etoposide / Q000494:pharmacology; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D005456:Fluorescent Dyes / Q000494:pharmacology; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D051379:Mice; D009368:Neoplasm Transplantation / Q000473:pathology; D017239:Paclitaxel / Q000031:analogs & derivatives* / Q000494:pharmacology; D019047:Phantoms, Imaging; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000473:pathology; D012964:Sodium; D012965:Sodium Chloride / Q000737:chemistry; D043823:Taxoids; D013997:Time Factors; D016896:Treatment Outcome; D014407:Tumor Cells, Cultured
chemical_list: D017304:Annexin A5; D000972:Antineoplastic Agents, Phytogenic; D005456:Fluorescent Dyes; D043823:Taxoids; D000077143:Docetaxel; D012965:Sodium Chloride; D005047:Etoposide; D012964:Sodium; D017239:Paclitaxel