Abstract 3380: Direct contact with perivascular tumor cells enhances integrin αvβ3 signaling and migration of endothelial cells

The secretion of soluble pro-angiogenic factors by tumor cells and stromal cells in the perivascular niche promotes the aggressive angiogenesis that is typical of glioblastoma (GBM), which requires endothelial cell (EC) migration. Here, we show that angiogenesis can also be promoted by a direct interaction between brain tumor cells, including tumor cells with cancer stem-like properties (CSCs), and ECs. The direct interaction between CSCs and ECs was mediated by binding of integrin αvβ3 expressed on ECs to the RGD-peptide in L1CAM expressed on CSCs. Using in vitro assays, we found that this interaction increased network formation and migration-associated signaling events in ECs, including activation of integrin αvβ3, FAK, bone marrow tyrosine kinase on chromosome X (BMX), p130CAS, ERK and JNK. Comparison of the effects of co-culturing CSCs with ECs versus the effects of conditioned media from CSCs co-cultured with ECs indicated that upstream and downstream effector activation was not attributed to a secreted factor(s). Activation of αvβ3 and BMX was required for migration stimulated by direct binding but not for migration stimulated by soluble factors. RGD-peptide treatment of mice with established intracerebral GBM xenografts significantly reduced the percentage of Sox2-positive tumor cells (consistent with CSCs) in close proximity to ECs, decreased integrin αvβ3 and BMX activation and p130CAS phosphorylation in the ECs, and reduced the vessel surface area. These results show that direct interactions between CSCs and ECs have potent effects on EC migration and reveal a previously unrecognized aspect of the regulation of angiogenesis in GBM that can impact therapeutic anti-angiogenic targeting.

Citation Format: Monica Burgett, Justin Lathia, Patrick Roth, Amy Nowacki, Elena Pugacheva, Ping Huang, Amit Vasanji, Li Meizhang, Tatiana Byzova, Tom Mikkelsen, Shideng Bao, Jeremy Rich, Michael Weller, Candece Gladson. Direct contact with perivascular tumor cells enhances integrin αvβ3 signaling and migration of endothelial cells. [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 3380.

FIP200 and Rb1 expression in CNS metastasis from breast cancer (CNS met): Potential predictors of patient outcome

2014

Background: Patients with CNS met have a poor outcome with significant variation in overall survival. No marker to predict survival exists. Rb1 is a negative regulator of the cell cycle, and FiP200 is an upstream signaling node that is distributed between the nucleus and cytoplasm. Nuclear FIP200 inhibits cell proliferation by promoting expression of Rb1, whereas cytoplasmic FIP200 promotes cell survival through autophagy. Previously FIP200 deletion/mutation has been reported in 20% of primary invasive breast cancer [BR ca] patients. FIP200 cellular localization and genetic alterations have not been examined in CNS met. Methods: A retrospective analysis of BR ca and CNS met was performed based on tissue availability from 2 institutions. FIP200 and Rb1 expression and localization was evaluated by immunohistochemistry. Genetic alterations were evaluated by DNA array analysis. Results: 80 patients (42 BR ca and 38 CNS met) were identified. Overall CNS met samples had significantly higher levels of cytoplasmic FIP200 as compared to BR ca (52% vs 24% respectively, p=0.0002) and increased expression of FIP200 around areas of hypoxia/necrosis, consistent with increased autophagy. There was also a significant increase in expression of nuclear FIP200 and Rb1 in the CNS met compared to BR ca (p=0.0007 and p=0.0055 respectively). Median survival from development of CNS met was longer in the group with high levels of nuclear Rb1; 14 (3-27) vs 20 (12-33) months (low expression < 20% vs high ≥ 20%, p=0.1). The same finding was observed with FIP200, longer survival was observed with high nuclear expression; 16 (7-33) vs 19 (0.4-27) months (low expression <20% vs high ≥ 20%, p=0.2). Our DNA analysis for copy number variation and LOH in CNS met revealed no deletion in Rb1 or FIP200. Conclusions: The pattern of expression of Rb1 and FIP200 in CNS met is different from BR ca. Notably, cytoplasmic FIP200 which promotes cell survival is highly expressed in CNS mets vs BR ca. This suggests metastatic breast cancer cells utilize autophagy as a survival mechanism. In addition, there is a trend to better survival of those patients with CNS met who express high nuclear FIP200 and Rb1, both of which have anti-proliferative roles in the nucleus.

Expression (Exp) of FIP200 and Rb in breast cancer (BreastCA) metastasis (met) to the brain

222

Background: BreastCA is the 2nd leading cause of cancer deaths in women in the US. Although the outcome for BreastCA with brain met remains poor, there is significant variation in overall survival (OS). Yet, there are no markers or models to predict OS. FIP200 regulates several pathways. In the nucleus, it inhibits cell proliferation by promoting Rb-1 and p21, and in the cytoplasm it promotes cell survival by inhibiting Pyk2 and regulating autophagy. It has been reported that FIP200 gene is deleted or mutated in 20% of primary BreastCAs, and its Exp is correlated with Rb1 levels. FIP200 Exp, its cellular localization, and gene alterations have not been examined in brain met of any cancer.

Methods: Brain met tissues of 21 BreastCA patients (pts) biopsied in our institution between 8/2000 and 3/2010 were obtained and Exp of FIP200 and Rb1 were analyzed. Biopsies were selected based on tissue adequacy and prior diagnosis (Dx) of invasive intra-ductal BreastCA. Immunohistochemistry (IHC) was used to evaluate the localization and Exp levels of FIP200 and Rb1 which in turn were tested as predictors of OS. Genetic alterations in FIP200 and Rb1 were examined after DNA extraction.

Results: Median time from Dx to met was 23 (range 0-245) months (mos), and median OS from Dx was 43 (range 6-264) mos. Nuclear Exp of Rb1 in < 30% vs. ≥ 30% of cells were seen in 11 vs. 10 pts. Median OS was 39 (range 6-264) mos for Rb1 Exp < 30% and 47 (range 20-190) mo for Rb1 Exp ≥ 30%. Nuclear Exp of FIP200 in <20% vs. ≥ 20% of cells were seen in 13 vs. 8 pts. Median OS was 39 (range 6-264) mo for FIP200 nuclear Exp <20% and 45 (range 43-122) mo for FIP200 Exp ≥ 20%. DNA analysis of 11 pts for copy number variations and loss of heterozygocity (LOH) showed no deletion mutations in FIP200 or Rb1, loss of p53 in 4 of 11, ErbB2 (Her-2) amplification in 4 of 11, and no EGFR gene mutations.

Conclusions: The nuclear Exp of Rb1 in brain met from invasive intra-ductal BreastCA may be linked OS. An expanded study is underway to define whether nuclear FIP200 in >20% of cells correlates with nuclear Rb and OS in BreastCA.

Elevated expression of TGF-beta1 in head and neck cancer-associated fibroblasts

Head and neck cancers are characterized by a vigorous desmoplastic response, but the contribution of stromal-derived growth factors to the tumor microenvironment is poorly understood. We evaluated the expression of stromal growth factor expression in head and neck squamous cell carcinoma (HNSCC) in normal and tumor-associated stromal cells. Stromal tissue was isolated from epithelial cells with laser capture microdissection (LCMD) and analyzed by cDNA array for the expression of TGFalpha, TGF-beta1, HGF, PDGF-alpha, IGFII, bFGF, aFGF, VEGFC, and VEGF. Primary fibroblasts were isolated in vitro from HNSCC tumors, adjacent histologically normal mucosa, and skin in vitro. Fibroblast populations were assessed for TGF-beta1 expression by ELISA and luciferase reporter assay to assess protein expression. We identified TGF-beta1 and IGFII overexpression in normal and tumor-associated stromal cells; however, only TGF-beta1 was significantly overexpressed (3.4-fold) in tumor-associated stroma. Assessment of carcinoma-associated fibroblasts (CAFs), normal dermal fibroblasts (NDFs), and normal mucosal fibroblasts (NMFs) in propagated fibroblasts demonstrated persistently elevated levels of TGF-beta1 in CAFs compared to NMF and NDF populations. Elevated levels of TGF-beta1 were identified in the stromal compartment of HNSCC tumors compared to normal mucosa by immunohistochemical analysis. These results suggest that TGF-beta1 mRNA and protein is specifically upregulated in CAFs in vitro and in vivo.

Paradoxical labeling of radiosurgically treated quiescent tumors with Ki67, a marker of cellular proliferation

Ki67 (also known as MIB) is a monoclonal antibody staining agent, which is routinely used as a marker of cellular proliferation. It is used to evaluate the proliferative potential of malignant tumors, since it is thought to stain only those cells undergoing active division. The paradoxical elevation of the Ki67 labeling index observed in radiosurgically treated benign and malignant tumors is reported. Ten patients, who had previously undergone either linac or Gamma Knife radiosurgery, underwent surgical resection for a radiographically quiescent tumor. One patient underwent autopsy after dying from complications of radiosurgery. All were thought to be suffering from adverse radiation effect (ARE) and were refractory to conservative management. None were thought to have a recurrent tumor. All of the resected tumors were subjected to analysis with Ki67 staining. Despite the radiographic stability of the tumors, all manifested significantly elevated populations of cells exhibiting positivity for Ki67 antigen. This staining pattern would suggest a significant proliferative potential, which did not match the observed clinical course. The literature is reviewed and possible mechanisms to explain the paradoxical findings are presented.