Early detection of squamous cell carcinoma in carcinogen induced oral cancer rodent model by ratiometric activatable cell penetrating peptides

Oral Oncol. 2017 Aug;71:156-162. doi: 10.1016/j.oraloncology.2017.06.009. Epub 2017 Jun 27.


Objectives: Ratiometric cell-penetrating-peptides (RACPP) are hairpin-shaped molecules that undergo cleavage by tumor-associated proteases resulting in measurable Cy5:Cy7 fluorescence ratiometric change to label cancer in vivo. We evaluated an MMP cleavable RACPP for use in the early detection of malignant lesions in a carcinogen-induced rodent tumor model.

Methods: Wild-type immune-competent mice were given 4-nitroquinoline-oxide (4NQO) for 16weeks. Oral cavities from live mice that had been intravenously administered MMP cleavable PLGC(Me)AG-RACPP were serially imaged from week 11 through week 21 using white-light reflectance and Cy5:Cy7 ratiometric fluorescence.

Results: In an initial study we found that at week 21 nearly all mice (13/14) had oral cavity lesions, of which 90% were high-grade dysplasia or invasive carcinoma. These high-grade lesions were identifiable with white light reflectance and RACPP Cy5:Cy7 ratiometric fluorescence with similar detectability, Area Under Curve (AUC) for RACPP detection was 0.97 (95% Confidence interval (CI)=0.92-1.02, p<0.001), sensitivity=89%, specificity=100%. In a follow up study, oral cavity lesions generated by 4NQO were imaged and histologically analyzed at weeks 16, 18 and 21. In this study we showed that RACPP-fluorescence detection positively identified 15 squamous cell carcinomas (in 6 separate mice) that were poorly visible or undetectable by white light reflectance.

Conclusions: RACPP ratiometric fluorescence can be used to accurately detect carcinogen-induced carcinoma in immunocompetent mice that are poorly visible or undetectable by white light reflectance.

Keywords: Carcinogen-induced head and neck squamous cell carcinoma; Enzyme responsive; In vivo; Matrix metalloproteinase; Ratiometricfluorescence imaging.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • 4-Nitroquinoline-1-oxide / toxicity*
  • Animals
  • Carcinogens / toxicity*
  • Carcinoma, Squamous Cell / chemically induced
  • Carcinoma, Squamous Cell / diagnosis*
  • Cell-Penetrating Peptides / metabolism*
  • Disease Models, Animal*
  • Female
  • Fluorescence
  • Mice
  • Mice, Inbred C57BL
  • Mouth Neoplasms / chemically induced
  • Mouth Neoplasms / diagnosis*
  • Sensitivity and Specificity


  • Carcinogens
  • Cell-Penetrating Peptides
  • 4-Nitroquinoline-1-oxide