Identification of AFAP1L1 as a prognostic marker for spindle cell sarcomas

Abstract

Spindle cell sarcomas consist of tumors with different biological features, of which distant metastasis is the most ominous sign for a poor prognosis. However, metastasis is difficult to predict on the basis of current histopathological analyses. We have identified actin filament-associated protein 1-like 1 (AFAP1L1) as a candidate for a metastasis-predicting marker from the gene expression profiles of 65 spindle cell sarcomas. A multivariate analysis determined that AFAP1L1 was an independent factor for predicting the occurrence of distant metastasis (P ¼ 0.0001), which was further confirmed in another set of 41 tumors by a quantitative mRNA expression analysis. Immunohistochemical staining using paraffin-embedded tumor tissues revealed that the metastasis-free rate was significantly better in tumors negative for AFAP1L1 (P ¼ 0.0093 by log-rank test). Knocking down the AFAP1L1 gene in sarcoma cells resulted in inhibition of the cell invasion, and forced expression of AFAP1L1 in immortalized human mesenchymal stem cells induced anchorage-independent growth and increased cell invasiveness with high activity levels of matrix metallopeptidase. Furthermore, tumor growth in vivo was accelerated in AFAP1L1-transduced sarcoma cell lines. These results suggest that AFAP1L1 has a role in the progression of spindle cell sarcomas and is a prognostic biomarker.

XB130—A Novel Adaptor Protein: Gene, Function, and Roles in Tumorigenesis

“…More interestingly, the adaptor proteins in the AFAP family, AFAP1 and AFAP1L1, are also involved in cancer. AFAP1, for instance, plays a significant role in breast cancer cell adhesion and in the tumorigenesis of prostate cancer [48, 49], whereas AFAP1L1 has been found to be involved in spindle cell sarcomas [50, 51]. Like these AFAP family members, several recent studies indicate that XB130 is also involved in tumorigenesis [36].…”

Regulation of sarcoma cell migration, invasion and invadopodia formation by AFAP1L1 through a phosphotyrosine-dependent pathway

“…27 These observations together with the ability of AFAP1L1 to directly bind the invadopodia/podosome marker cortactin 8 , associate with vinculin (found at focal adhesions as well as invadopodia) 26 and the fact that AFAP1L1 encompasses a homologous site to that which is phosphorylated by protein kinase C in AFAP1 (which regulates podosome and potentially invadopodia lifespan), 11 we now have significant evidence for placing AFAP1L1 as a crucial regulator of invadpodia in sarcoma cells, and that it directly intersects multiple critical invadopodia regulatory networks. The strongest evidence for the importance of AFAP1L1 for invadopodia regulation, from other investigators 8,9,26 and as we report here, relates to the U2OS cell line. This suggests there are important cell type-specific ancillary components that may be direct interacting partners of AFAP1L1, which help mediate this cell-specific phenotype.…”

“…1,[45][46][47] In addition, our data show that signaling from AFAP1L1 is modulated by a cell's contact with the extracellular matrix, which could explain the differential effects on cell growth in twodimensional monolayer cultures (which show no major effects on cell proliferation) compared with three-dimensional and in vivo cultures (which show significant effects on proliferation/survival) of cells over/underexpressing AFAP1L1. 8,26 Although high expression of total AFAP1L1 is associated with sarcomas (and colorectal cancer progression), 8,26 it will be important to determine whether the activation status (that is, phosphorylation of Y136 and Y566 sites, for which we have generated specific antibodies) also correlate with disease status and clinical outcomes. Important clinical applications of the molecular understanding we now have of the AFAP1L1 pathway need to be addressed through the use of both advanced cancer mouse models with altered AFAP1L1 (for example, sarcomas bearing wild-type or Y136/566F mutant AFAP1L1) and identifying therapeutic avenues to disrupt the AFAP1L1 pathway in sarcoma and potentially other (for example, colorectal cancer) patients.…”

“…7 Several actin-binding adaptor proteins are used in the initiation, assembly and maturation of invadopodia, including the recently characterized actin filament-associated protein (AFAP) family. 8,9 As with the actin-related protein complex-2/3 and cortactin, the neuronal Wiskott-Aldrich syndrome protein (N-WASp) binding adaptor, 10 AFAP family members are SFK substrates that localize to invadopodia. 9,11 SFK regulate invadopodia initiation and assembly downstream of receptor tyrosine kinases and integrins by stimulating GTPases such as Rac1 and cdc42, 12 as well as via phosphorylating substrates/ scaffolds such as tyrosine kinase substrate-5 (Tks5).…”

The Transcription Factor Sp3 Regulates the Expression of a Metastasis-Related Marker of Sarcoma, Actin Filament-Associated Protein 1-Like 1 (AFAP1L1)

“…AFAP1L1 was previously identified as a metastasis-predicting marker from the gene-expression profiles of 65 spindle cell sarcomas by our group [1]. In univariate and multivariate analyses, higher expression of AFAP1L1 was found to contribute to the occurrence of distant metastases, along with patient age and tumor grade.…”