Abstract 4107: CD44 expressing cancer associated fibroblasts guide collagen 1 fibers in breast cancer

Cluster of differentiation 44 (CD44) has been identified as a cancer stem cell marker in breast [1], pancreatic, prostate, ovarian, and colon cancer [2] making it a significantly important molecule for investigating and targeting. CD44 is abundant in triple negative breast cancer (TNBC), and its expression is a poor prognosticator for outcome [3]. Stromal cells play a critical role in tumor progression [4]. Amongst these, cancer associated fibroblasts (CAFs) significantly influence the proliferation, invasion, and metastasis of cancer cells [5]. CAFs are a major source of collagen 1 (Col1) fibers in the tumor stroma, play a role in cancer cell dissemination, and contribute to the reactive desmoplastic tumor stroma, and the high density and stiffness of the tumor extracellular matrix (ECM) [6]. Here we investigated the relationship between CD44 expression and Col1 fibers in a human breast cancer tissue microarray (TMA). We found that CD44 was expressed by cancer cells and CAFs in the TMA. CD44 expressing CAFs were seen guiding Col1 fibers. A breast tissue microarray containing stage I-IV human breast cancers and normal adjacent biopsy samples was used in this study. CD44 immunostaining was performed on 5μm thick sections following which Col1 fiber distribution was obtained from the same section using second harmonic generation (SHG) microscopy. Z-stacks of SHG tile images were acquired on Olympus FV1000MPE multiphoton microscope using a 25x lens. A high-resolution digital scan of the CD44 stained slide was acquired. CD44 and Col1 fiber images were co-registered and overlaid to evaluate co-localization patterns. 8/12 stage I cancers showed high (3+) CD44 staining intensities, 45/62 stage II cancers showed high (3+) staining intensities, 14/16 stage III cancers showed high (3+) staining intensities and 1/1 stage IV cancer showed high (3+) staining intensities. Col1 fibers patterns changed from short and thick in normal adjacent tissue to long, thin and straight fibers in malignant tissue. We observed strong expression of CD44 in breast cancer cells and in CAFs that were closely associated with straight long Col1 fibers that are typical of an invasive metastatic ECM phenotype. CD44 expressing CAFs were found attached to the Col1 fibers and appeared to guide fibers through the cancer cells. We are currently performing advanced texture analysis to characterize the differences in distribution patterns. Our data highlight the importance of CD44 as a target in TNBC to eliminate cancer cells and CAFs. CD44 targeting may also change Col1 fiber patterns to a less aggressive ECM phenotype. 1. Al-Hajj M et al., PNAS 2003; 2. Kim GR et al., Oncology letters. 2015; 3. Idowu MO et al., Hum Pathol. 2012; 4. Quail DF et al., Nat Med. 2013; 5. Kalluri R et al., Nature reviews Cancer. 2006; 6. Byun JS et al., Am J Pathol. 2013. Citation Format: Samata Kakkad, Desmond Jacob, Balaji Krishnamachary, Zaver M. Bhujwalla. CD44 expressing cancer associated fibroblasts guide collagen 1 fibers in breast cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4107.