Targeting collagen XVIII improves the efficiency of ErbB inhibitors in breast cancer models
Raman Devarajan, Valerio Izzi, Hellevi Peltoketo, Gunilla Rask, Saila Kauppila, Marja-Riitta Väisänen, Heli Ruotsalainen, Guillermo Martínez-Nieto, Sanna-Maria Karppinen, Timo Väisänen, Inderjeet Kaur, Jussi Koivunen, Takako Sasaki, Robert Winqvist, Aki Manninen, Fredrik Wärnberg, Malin Sund, Taina Pihlajaniemi, Ritva Heljasvaara
Raman Devarajan, Valerio Izzi, Hellevi Peltoketo, Gunilla Rask, Saila Kauppila, Marja-Riitta Väisänen, Heli Ruotsalainen, Guillermo Martínez-Nieto, Sanna-Maria Karppinen, Timo Väisänen, Inderjeet Kaur, Jussi Koivunen, Takako Sasaki, Robert Winqvist, Aki Manninen, Fredrik Wärnberg, Malin Sund, Taina Pihlajaniemi, Ritva Heljasvaara
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Research Article Oncology

Targeting collagen XVIII improves the efficiency of ErbB inhibitors in breast cancer models

Abstract

The tumor extracellular matrix (ECM) critically regulates cancer progression and treatment response. Expression of the basement membrane component collagen XVIII (ColXVIII) is induced in solid tumors, but its involvement in tumorigenesis has remained elusive. We show here that ColXVIII was markedly upregulated in human breast cancer (BC) and was closely associated with a poor prognosis in high-grade BCs. We discovered a role for ColXVIII as a modulator of epidermal growth factor receptor tyrosine kinase (ErbB) signaling and show that it forms a complex with ErbB1 and -2 (also known as EGFR and human epidermal growth factor receptor 2 [HER2]) and α6-integrin to promote cancer cell proliferation in a pathway involving its N-terminal portion and the MAPK/ERK1/2 and PI3K/AKT cascades. Studies using Col18a1 mouse models crossed with the mouse mammary tumor virus–polyoma virus middle T antigen (MMTV-PyMT) mammary carcinogenesis model showed that ColXVIII promoted BC growth and metastasis in a tumor cell–autonomous manner. Moreover, the number of mammary cancer stem cells was significantly reduced in the MMTV-PyMT and human cell models upon ColXVIII inhibition. Finally, ablation of ColXVIII substantially improved the efficacy of ErbB-targeting therapies in both preclinical models. In summary, ColXVIII was found to sustain the stemness properties of BC cells and tumor progression and metastasis through ErbB signaling, suggesting that targeting ColXVIII in the tumor milieu may have important therapeutic potential.

Authors

Raman Devarajan, Valerio Izzi, Hellevi Peltoketo, Gunilla Rask, Saila Kauppila, Marja-Riitta Väisänen, Heli Ruotsalainen, Guillermo Martínez-Nieto, Sanna-Maria Karppinen, Timo Väisänen, Inderjeet Kaur, Jussi Koivunen, Takako Sasaki, Robert Winqvist, Aki Manninen, Fredrik Wärnberg, Malin Sund, Taina Pihlajaniemi, Ritva Heljasvaara

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Figure 5

Expression of cytokeratins in PyMT tumors and orthotopic allograft transplantation experiments.

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Expression of cytokeratins in PyMT tumors and orthotopic allograft trans...
(A) Representative images of immunostaining of CK8 and CK14 in WT-PyMT, 18–/–-PyMT, P1-PyMT, and P2-PyMT tumors. (B) Quantification of CK8+ luminal cells in WT-PyMT and 18–/–-PyMT tumors. (C) Quantification of CK14+ basal cells in WT-PyMT, 18–/–-PyMT, P1-PyMT, and P2-PyMT tumors. In B and C, n = 6/genotype; n = 4 random fields/tumor at ×20. (D) Growth rates of transplanted WT-PyMT and 18–/–-PyMT tumors in WT and Col18a1–/– hosts. Number of mice (N) and allograft tumors (n): WT-PyMT cells in WT hosts and 18–/–-PyMT cells in WT hosts (N = 12, n = 24), WT-PyMT cells in Col18a1–/– hosts and 18–/–-PyMT cells in Col18a1–/– hosts (N = 6, n = 12). (E) Representative images of Ki67 immunostaining in WT-PyMT and 18–/–-PyMT allografts. (F) Quantification of the Ki67+ cell counts in transplanted tumors (n = 6/group, n = 4 random fields/tumor at ×20). (G) Representative images of ColXVIII (green) and αSMA (red) expression in allograft tumors. Arrowheads indicate ColXVIII+ structures or cells at tumor borders; open arrowheads show αSMA+ cells; yellow arrows point to αSMA and ColXVIII double-positive structures and cells; white arrows indicate αSMA+ blood vessels. Scale bars: 200 μm (A, E, and G). DAPI, blue. *P < 0.05, **P < 0.01, and ***P < 0.01, by 2-tailed Student’s t test (B and D) and 2-way ANOVA with Dunnett’s multiple-comparison test (C and F). Error bars indicate the SEM.