Background: The transcription factor Nanog is crucial for the self-renewal of cancer stem-like cells (CSCs). Nanog expression in colorectal cancer (CRC) tissue correlates with lymph node metastasis and poor prognosis. Since Nanog is not expressed in most tissues, including normal adult stem-cells, it represents a therapeutic target specific to cancer cells. Curcumin inhibits proliferation and expansion of CSCs derived from CRC and adenomas. In NOD/SCID mice bearing xenografts from patient-derived CRC CSCs, curcumin significantly inhibited tumour growth and improved survival. In addition, curcumin binds directly to Nanog recombinant protein (quantified using microscale thermophoresis). We have developed 3D in-vitro primary human explant models to further characterise the effects of curcumin on Nanog. In this work the hypothesis is tested that Nanog may be an early marker of response for CRC prevention agents.

Methods: Patient-derived CRC and adenoma tissue was cubed (2x2x2mm) and treated for 24 hours with curcumin. Following treatment, explant tissues were processed for analysis by immunohistochemistry (IHC) (n=6) and flow cytometry (n=17). The effect of curcumin on CSCs (defined by expression of aldehyde dehydrogenase (ALDH) or Nanog) and differentiation (via Mucin 2 expression) was analysed using IHC. Additionally, cells expressing Nanog (Nanog+) or Nanog plus proliferation marker Ki67 (Nanog+Ki67+) were assessed using flow cytometry.

Results: A range of adenoma (n=5) and Dukes stage A-C CRC (n=18) samples were studied. Following exposure to curcumin, a 30% reduction was observed in Nanog+ and Nanog+Ki67+ cells. Nanog+ cell number was decreased in a curcumin concentration-dependent fashion in 6 samples and concentration-independently in a further 8. No response was observed in 3 samples. A reduction in Nanog and ALDH with concurrent increase in differentiation was observed via IHC in one sample.

Conclusion: Our data suggest Nanog is targeted by curcumin in adenoma and CRC tissues. Nanog may serve as a biomarker in clinical trials to identify individuals most amenable to treatment with curcumin alone or in combination treatment. Crucially, this will help select those who are likely to benefit from curcumin as a cancer prevention agent. Ultimately, this concept may be applicable to the evaluation of novel CRC prevention agents.

Citation Format: Sam Khan, Ankur Karmokar, Zahirah Sidat, Nalini Foreman, David Moore, Jennifer Higgins, Emma Parrott, Despoina Theofanous, Dominic Hobbs, Lynne Howells, Anne Thomas, Karen Brown. Targeting Nanog in 3D explant models for the evaluation of cancer prevention agents [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 258.