Imaging, biodistribution and therapy potential of halogenated tamoxifen analogues.
Tamoxifen binds to estrogen receptors (ERs) and prevents breast cancer cell proliferation. This study is aimed at developing a ligand for imaging ER (+) breast tumors by positron emission tomography (PET) or single photon emission computed tomography (SPECT). [18F]-Labeled tamoxifen analogue ([18F]FTX) was prepared in 30-40% yield and [131I]-labeled tamoxifen analogue ([131I]ITX) was prepared in 20-25% yield. In mammary tumor-bearing rats, the biodistribution of [18F]FTX at 2 h showed a tumor uptake value (% injected dose/gram tissue) of 0.41 +/- 0.07; when rats were pretreated with diethylstilbestrol (DES), the value changed to 0.24 +/- 0.017. [131I]ITX at 6 h showed a tumor uptake value of 0.26 +/- 0.166; when rats were pretreated with DES, the value changed to 0.22 +/- 0.044. Priming tumor-bearing rats with estradiol, a tumor uptake value for [131I]ITX was increased to 0.48 +/- 0.107 at 6 h. In the [3H]estradiol receptor assay, tumors had a mean estrogen receptor density of 7.5 fmol/mg of protein. In gamma scintigraphic imaging studies with [131I]ITX, the rabbit uterus uptake can be blocked by pretreatment with DES. Both iodo-tamoxifen and tamoxifen reduced ER(+) breast tumor growth at the dose of 50 micrograms in tumor-bearing mice. The findings indicate that tamoxifen analogue uptake in tumors occurs via an ER-mediated process. Both analogues should have potential for diagnosing functioning ER(+) breast cancer.
Yang
D J
DJ
Division of Diagnostic Imaging, University of Texas M.D. Anderson Cancer Center, Houston 77030.
Li
C
C
Kuang
L R
LR
Price
J E
JE
Buzdar
A U
AU
Tansey
W
W
Cherif
A
A
Gretzer
M
M
Kim
E E
EE
Wallace
S
S
D000818:Animals; D001345:Autoradiography; D001943:Breast Neoplasms / Q000000981:diagnostic imaging; D005260:Female; D005462:Fluorine Radioisotopes; D006801:Humans; D007457:Iodine Radioisotopes; D008325:Mammary Neoplasms, Experimental / Q000000981:diagnostic imaging* / Q000188:drug therapy; D008875:Middle Aged; D051381:Rats; D011916:Rats, Inbred F344; D017207:Rats, Sprague-Dawley; D011960:Receptors, Estrogen / Q000032:analysis; D013629:Tamoxifen / Q000031:analogs & derivatives* / Q000493:pharmacokinetics / Q000627:therapeutic use; D014018:Tissue Distribution; D014055:Tomography, Emission-Computed; D015899:Tomography, Emission-Computed, Single-Photon; D014407:Tumor Cells, Cultured
D005462:Fluorine Radioisotopes; D007457:Iodine Radioisotopes; D011960:Receptors, Estrogen; D013629:Tamoxifen; C037726:4-fluorotamoxifen; C035179:iodotamoxifen