A genetic strategy for combined screening and localized imaging of breast cancer.
OBJECTIVE
Improvements are needed for the early detection of breast cancer, as current imaging methods lack sensitivity to detect small tumors and assess their disease phenotype.


METHODS
To address this issue, the dual reporter adenoviral vector (Ad5/3-Id1-SEAP-Id1-mCherry) was produced with a cancer-specific Id1 promoter driving expression of a blood-based screening reporter (secreted embryonic alkaline phosphatase, SEAP) and a fluorescent imaging reporter (mCherry). This diagnostic system was assessed for its screening potential on breast cancer cell lines of various aggressive phenotypes. Reporter expression was measured and correlated with promoter level expression using Western blot. Adenovirus receptor expression was normalized against reporter expression with luciferase infectivity assays. Ad5/3-Id1-SEAP-Id1-mCherry infected MDA-MB-231 cells combined with uninfected cells were implanted into the mammary fat pad of athymic nude mice to recapitulate low-dose tumor delivery. Id1 driven SEAP expression and mCherry imaging were monitored to validate diagnostic sensitivity and efficacy.


RESULTS
Infected breast cancer cell lines displayed SEAP levels in the media that were 10-fold above background by 2 days after infection. Ad5/3-Id1-SEAP-Id1-mCherry infected cells (multiplicity of infection = 10) implanted in athymic nude mice demonstrated a 14-fold increase in serum SEAP levels over baseline when as little as 2.5% of the tumor contained infected cells. This robust response was also found for the mCherry reporter, which was clearly visible in tumor xenografts on day 2 post implantation.


CONCLUSIONS
This diagnostic system that combines screening with imaging for early detection and monitoring of breast cancer can be easily extended to other reporters/modalities and cancer-targeting methods. Combining screening with imaging in a genetic, cancer-specific mechanism allows sensitive multi-modal detection and localization of breast cancer.
Warram
Jason M
JM
Department of Pathology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA.
Borovjagin
Anton V
AV
School of Dentistry, University of Alabama at Birmingham, Birmingham, AL, 35294, USA.
Zinn
Kurt R
KR
Department of Pathology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA. kurtzinn@uab.edu.|Department of Radiology, University of Alabama at Birmingham, Birmingham, AL, 35294, USA. kurtzinn@uab.edu.
D000256:Adenoviridae / Q000235:genetics; D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D001943:Breast Neoplasms / Q000175:diagnosis* / Q000235:genetics* / Q000473:pathology; D045744:Cell Line, Tumor; D003470:Culture Media; D003952:Diagnostic Imaging / Q000379:methods*; D005260:Female; D017930:Genes, Reporter / Q000235:genetics; D005821:Genetic Techniques; D006801:Humans; D051798:Inhibitor of Differentiation Protein 1 / Q000378:metabolism; D008403:Mass Screening / Q000379:methods*; D051379:Mice; D008819:Mice, Nude; D009361:Neoplasm Invasiveness; D010641:Phenotype; D044967:Serum; D013997:Time Factors; D023041:Xenograft Model Antitumor Assays
D003470:Culture Media; D051798:Inhibitor of Differentiation Protein 1; D000469:Alkaline Phosphatase