Abstract | UNLABELLED: Early assessment of the efficacy of treatment is important in patients with breast cancer, whose routine adjuvant regimen frequently includes chemotherapy. Irrespective of the exact mechanisms involved in induction, the common early phenotypic marker of apoptosis is the expression on the outer cell membrane surface of phosphatidylserine, which avidly binds annexin V. (99m)Tc-labeled annexin V has been proposed for in vivo scintigraphic detection of apoptosis, albeit with contradicting results. This study was performed to define the time course of apoptosis induced by the chemotherapeutic agent paclitaxel in a model of virus-induced murine breast cancer. METHODS: RESULTS: Baseline uptake of (99m)Tc-annexin V in breast tumors was about 2-fold higher than the uptake in normal breast tissue (demonstrating some ongoing apoptosis); tracer uptake increased at 1 and 3 h after paclitaxel administration (to almost double the baseline value) and then declined to levels even lower than baseline. Although no activation of the apoptosis-inducing factor mechanism was detected, a peak in TUNEL-positive tumor cells was reached 3 h after paclitaxel administration (to more than 6-fold the baseline level). The antiapoptotic marker Bcl-2 exhibited a biphasic pattern, with a maximum drop at 3 h, followed by return toward baseline levels at 6 h. CONCLUSION: These results define the time course of various biologic events taking place in this model of murine breast cancer after a proapoptotic insult (single-dose paclitaxel). Although confirming that in vivo uptake of (99m)Tc-annexin V reflects the degree of apoptosis, the study also suggests that the apoptotic response to antitumor therapy may differ from tumor type to tumor type. Therefore, contradicting results previously reported may depend on an inadequate time window chosen for imaging with (99m)Tc-annexin V.
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Authors | Paola A Erba, Chiara Manfredi, Elena Lazzeri, Fabrizio Minichilli, Ernest K J Pauwels, Alberto Sbrana, H William Strauss, Giuliano Mariani |
Journal | Journal of nuclear medicine : official publication, Society of Nuclear Medicine
(J Nucl Med)
Vol. 51
Issue 5
Pg. 775-81
(May 2010)
ISSN: 1535-5667 [Electronic] United States |
PMID | 20395330
(Publication Type: Journal Article)
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Chemical References |
- Annexin A5
- Antineoplastic Agents, Phytogenic
- Apoptosis Inducing Factor
- Organotechnetium Compounds
- Proto-Oncogene Proteins c-bcl-2
- Radiopharmaceuticals
- technetium Tc 99m annexin V
- Caspase 3
- Paclitaxel
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Topics |
- Animals
- Annexin A5
(pharmacokinetics)
- Antineoplastic Agents, Phytogenic
(therapeutic use)
- Apoptosis
(drug effects)
- Apoptosis Inducing Factor
(metabolism)
- Blotting, Western
- Caspase 3
(metabolism)
- Female
- In Situ Nick-End Labeling
- Mammary Neoplasms, Experimental
(diagnostic imaging, drug therapy, virology)
- Mammary Tumor Virus, Mouse
- Mice
- Mice, Inbred BALB C
- Neoplasm Transplantation
- Organotechnetium Compounds
(pharmacokinetics)
- Paclitaxel
(therapeutic use)
- Proto-Oncogene Proteins c-bcl-2
(metabolism)
- Radionuclide Imaging
- Radiopharmaceuticals
(pharmacokinetics)
- Tissue Distribution
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