Complement C1r/C1s, Uegf, Bmp1 (CUB) domain-containing protein 1 (CDCP1) is a transmembrane protein that regulates anchorage-independent growth and cancer cell migration and invasion. Expression of CDCP1 is detected in a number of cancer cell lines and tissues and is closely correlated with poor prognosis. Invadopodia are actin-based protrusions on the surface of invasive cancer cells that promote the degradation of the extracellular matrix (ECM) via localized proteolysis, which is mainly mediated by membrane type 1 matrix metalloproteinase (MT1-MMP). MT1-MMP is accumulated at invadopodia by targeted delivery via membrane trafficking. The present study shows that CDCP1 is required for ECM degradation by invadopodia in human breast cancer and melanoma cells. CDCP1 localized to caveolin-1-containing vesicular structures and lipid rafts and was detected in close proximity to invadopodia. Further biochemical analysis revealed that substantial amounts of CDCP1 existed in the Triton X-100 insoluble lipid raft fraction. CDCP1 was coimmunoprecipitated with MT1-MMP and colocalized with MT1-MMP at the vesicular structures. The siRNA-mediated knockdown of the CDCP1 expression markedly inhibited MT1-MMP-dependent ECM degradation and Matrigel invasion and reduced the accumulation of MT1-MMP at invadopodia, as shown by immunofluorescence analysis. These results indicate that CDCP1 is an essential regulator of the trafficking and function of MT1-MMP-and invadopodia-mediated invasion of cancer cells. Mol Cancer Res; 11(6); 628-37.

Scirrhous gastric carcinoma (SGC) has the worst prognosis of all gastric cancers, owing to its rapid expansion by invasion and frequent peritoneal dissemination. Due to the increased proliferation of stromal fibroblasts (SFs) that occurs within SGC lesions and the peritoneal metastatic sites, SFs have been proposed to support the progression of this disease. However, the biological and molecular basis and the pathological role of the intercellular interaction between SGC cells and SFs remain largely unknown. In this study, we investigated the role of SFs in the invasion of the extracellular matrix (ECM) by SGC cells. When SGC cells were cocultured with SFs derived from SGC tissue on three-dimensional (3D) Matrigel, they were attracted together to form large cellular aggregates that invaded within the Matrigel. Time-lapse imaging revealed that this process was associated with extensive contraction and remodeling of the ECM. Immunofluorescence and biochemical analysis showed that SGC cells stimulate phosphorylation of myosin light chain and actomyosin-mediated mechanical remodeling of the ECM by SFs. By utilizing this assay system for inhibitor library screening, we have identified several inhibitors that potently suppress the cooperation between SGC cells and SFs to form the invasive structures. Among them, a Src inhibitor dasatinib impaired the interaction between SGC cells and SFs both in vitro and in vivo and effectively blocked peritoneal dissemination of SGC cells. These results indicate that SFs mediate mechanical remodeling of the ECM by SGC cells, thereby promoting invasion and peritoneal dissemination of SGC.

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Diffuse-type gastric carcinomas (DGC) exhibit more aggressive progression and poorer prognosis than intestinal-type and other gastric carcinomas. To identify potential therapeutic targets, we examined protein tyrosine phosphorylation in a panel of DGC and other gastric cancer cell lines. Protein tyrosine phosphorylation was significantly enhanced or altered in DGC cell lines compared with that in other gastric cancer cell lines. Affinity purification and mass spectrometry analysis of tyrosine-phosphorylated proteins identified Met as a protein that is preferentially expressed and phosphorylated in DGC cell lines. Unexpectedly, Met inhibitors blocked cell growth, Met downstream signaling and peritoneal dissemination in vivo in only a subset of cell lines that exhibited remarkable overexpression of Met. Likewise, only cell lines with overexpression of fibroblast growth factor receptor 2 (FGFR2) or phosphorylation of FRS2 were sensitive to an FGFR2 inhibitor. A Src inhibitor saracatinib impaired growth in cell lines that are insensitive to both Met and FGFR2 inhibitors. Saracatinib also effectively impaired peritoneal dissemination of Met-independent and FGFR2-independent SGC cells. Moreover, DGC cell lines exhibited nearly mutually exclusive susceptibility to Met, FGFR and Src inhibitors. These results suggest that DGC have distinct sensitivities to molecular target drugs and that targeting Src is beneficial in the treatment of DGC insensitive to Met and FGFR inhibition.

<div>Abstract<p>Complement C1r/C1s, Uegf, Bmp1 (CUB) domain-containing protein 1 (CDCP1) is a transmembrane protein that regulates anchorage-independent growth and cancer cell migration and invasion. Expression of CDCP1 is detected in a number of cancer cell lines and tissues and is closely correlated with poor prognosis. Invadopodia are actin-based protrusions on the surface of invasive cancer cells that promote the degradation of the extracellular matrix (ECM) via localized proteolysis, which is mainly mediated by membrane type 1 matrix metalloproteinase (MT1-MMP). MT1-MMP is accumulated at invadopodia by targeted delivery via membrane trafficking. The present study shows that CDCP1 is required for ECM degradation by invadopodia in human breast cancer and melanoma cells. CDCP1 localized to caveolin-1–containing vesicular structures and lipid rafts and was detected in close proximity to invadopodia. Further biochemical analysis revealed that substantial amounts of CDCP1 existed in the Triton X-100 insoluble lipid raft fraction. CDCP1 was coimmunoprecipitated with MT1-MMP and colocalized with MT1-MMP at the vesicular structures. The siRNA-mediated knockdown of the CDCP1 expression markedly inhibited MT1-MMP–dependent ECM degradation and Matrigel invasion and reduced the accumulation of MT1-MMP at invadopodia, as shown by immunofluorescence analysis. These results indicate that CDCP1 is an essential regulator of the trafficking and function of MT1-MMP- and invadopodia-mediated invasion of cancer cells. <i>Mol Cancer Res; 11(6); 628–37. ©2013 AACR</i>.</p></div>

<p>PDF File-215K, CDCP1 is required for invadopodia-mediated ECM degradation by RPMI7951 human melanoma cells.</p>

<div>Abstract<p>Complement C1r/C1s, Uegf, Bmp1 (CUB) domain-containing protein 1 (CDCP1) is a transmembrane protein that regulates anchorage-independent growth and cancer cell migration and invasion. Expression of CDCP1 is detected in a number of cancer cell lines and tissues and is closely correlated with poor prognosis. Invadopodia are actin-based protrusions on the surface of invasive cancer cells that promote the degradation of the extracellular matrix (ECM) via localized proteolysis, which is mainly mediated by membrane type 1 matrix metalloproteinase (MT1-MMP). MT1-MMP is accumulated at invadopodia by targeted delivery via membrane trafficking. The present study shows that CDCP1 is required for ECM degradation by invadopodia in human breast cancer and melanoma cells. CDCP1 localized to caveolin-1–containing vesicular structures and lipid rafts and was detected in close proximity to invadopodia. Further biochemical analysis revealed that substantial amounts of CDCP1 existed in the Triton X-100 insoluble lipid raft fraction. CDCP1 was coimmunoprecipitated with MT1-MMP and colocalized with MT1-MMP at the vesicular structures. The siRNA-mediated knockdown of the CDCP1 expression markedly inhibited MT1-MMP–dependent ECM degradation and Matrigel invasion and reduced the accumulation of MT1-MMP at invadopodia, as shown by immunofluorescence analysis. These results indicate that CDCP1 is an essential regulator of the trafficking and function of MT1-MMP- and invadopodia-mediated invasion of cancer cells. <i>Mol Cancer Res; 11(6); 628–37. ©2013 AACR</i>.</p></div>

Invadopodia are ventral membrane protrusions that are formed by invasive cancer cells cultured on physiological substrates. They are actin-based structures and promote the degradation of the extracellular matrix by focally localizing matrix metalloproteinases. Accumulating evidence suggests that invadopodia play an important role in local invasion and distant metastasis of malignant tumors. Actinin is an actin-binding protein that forms dimers and crosslinks actin filaments. There are four isoforms of actinin in mammals and they are divided into the muscle type (actinin-2 and -3) and the non-muscle type (actinin-1 and -4). Actinin-1 is ubiquitously expressed and involved in the formation of focal adhesions, while actinin-4 is strongly expressed at the invading front of advanced cancers and its expression is correlated with poor prognosis. Although actinin-4 is thought to regulate cell motility and invasion, the detailed molecular mechanisms remain unclear. Moreover, functional differences between the two isoforms have yet to be fully defined. In this study, we studied the roles of and functional differences between actinin-1 and -4 in invadopodia formation to determine the impact of actinin-4 expression on cancer cells. Immunofluorescence analysis showed that both actinin-1 and -4 clearly localized at invadopodia in RPMI-7951 human melanoma cells and there was no obvious difference in their localization patterns. Likewise, invadopodia formation and degradation of fluorescent gelatin matrix were blocked by siRNA-mediated knockdown of either actinin-1 or -4. In contrast, only actinin-4, but not actinin-1, promoted invadopodia-mediated gelatin degradation activity when overexpressed in RPMI7951 cells. Similar results were obtained when MDA-MB-231 human breast cancer cells and SCC61 human head and neck squamous cell carcinoma cells were analyzed in the same manner. These results indicate that both actinin-1 and -4 are essential components of invadopodia, but only actinin-4 possesses an ability to promote invadopodia formation. Therefore, further analysis is conducted now to identify the unique functions actinin-4 in invadopodia formation. Citation Format: Yuumi Ito, Hideki Yamaguchi, Kiyoko Fukami, Kazufumi Honda, Nami Miura, Tesshi Yamada, Ryuichi Sakai. Functional differences of actinin isoforms in the formation of invadopodia by invasive cancer cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4070. doi:10.1158/1538-7445.AM2014-4070