Abstract 43: The role of discoidin domain receptor 2 (DDR2) and its relationship with procollagen alpha 1 type 1(Col1A1) in malignant glioma

We have previously shown that Col1A1 expression is found more frequently in low to intermediate grade glioma than high grade glioma(Cancer invest. 23:577,2005). On the other hand, its receptor DDR1 is found in high grade glioma and often signifies poor prognosis. We hypothesize that DDR2 which also binds to Col1A1 may play a role in mediating this complex relationship. We have investigated this relationship using 3 cell lines (2 cell lines, Glioma 1 and U-118, both express both Col1A1 and DDR1&2, A-172 which does not express Col1A1 but does express both DDR1&2). All cell lines were maintained in EMEM with 10% FCS. Treatment with Befeldin A (BFA), which blocks Col1a1 to the cell surface, results in ER stress with increase in GRP78 and growth inhibition in all three cell lines. U-118 was the most sensitive (ID50 of 9 ng/ml for U- 118, Glioma 1 (13ng/ml), and A-172 (24ng/ml)). Silencing Col1A1 resulted in decreased DDR1 & 2 in Glioma 1 and U-118 and decreased sensitivity to BFA by 20% for Glioma 1 and 10% in U-118. Silencing Col1 A1 resulted in G2M arrest and decrease in ERK1/2, JNK, and c-Jun, but increase in PDGF, CREB and P70 by protein array analysis and confirmed by Western blot. We further investigated the biological effect of silencing either DDR1 (primary DDR1a which is the major isoform found in Glioma 1 and DDR2). We found that silencing DDR 1 had no effect on DDR2 expression and vice versa. Interestingly, in contrast to silencing Col1A1, silencing either DDR1 or 2 had no effect on Col1A1 expression in Glioma 1 and U-118 and also no effect on cell cycle or cellular proliferation. In addition, silencing DDR1 or 2 led to decreased sensitivity to BFA for both Glioma and U-118 with increase in ID50 by 35-50% respectively. Furthermore, we have also found an increase in p-AKT, p-38, JNK and p-Jun after 48-hr post silencing of DDR2 while silencing DDR1 had minor effect. However, these proteins decreased after BFA treatment. In contrast, silencing DDR1 or DDR2 led to increased sensitivity to BFA in A-172 cells with reduction of ID50 by 20%. In addition, a decrease in p-AKT, p-38 and ERK were also seen. Silencing DDR1 or DDR2 also showed significant reduction in invasion in A-172 cell line, while minimal changes were seen in Glioma 1 and U-118. Since DDR1 has multiple subfamilies, while DDR1a is the most common one in brain tumor, it is possible that silencing one subfamily may upregulate the other subfamily. However, DDR2 has only one family and may explain the more profound effect in silencing DDR2. Taken together, our data suggest that the function of DDR2 is different among cell lines, and may be dictated by the presence of Col1A1 which is present in certain malignant glioma. We are currently investigating the possible mechanism(s) involved. Future targeted therapy in malignant glioma will need to take into consideration the different functions of DDR2. (Supported by Wanfang Hospital-Taipei medical university fellowship award and VA research grant) Citation Format: Shumei Chen, Chunjing Wu, Ying Ying Li, Medhi Wangpaichitr, Lynn G. Feun, Ronald Benveniste, Vy Dinh, Niramol Savaraj. The role of discoidin domain receptor 2 (DDR2) and its relationship with procollagen alpha 1 type 1(Col1A1) in malignant glioma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 43. doi:10.1158/1538-7445.AM2015-43