Native human autoantibodies targeting GIPC1 identify differential expression in malignant tumors of the breast and ovary

GIPC1 regulates MACC1-driven metastasis

Background

Identification of cancer metastasis-relevant molecular networks is desired to provide the basis for understanding and developing intervention strategies. Here we address the role of GIPC1 in the process of MACC1-driven metastasis. MACC1 is a prognostic indicator for patient metastasis formation and metastasis-free survival. MACC1 controls gene transcription, promotes motility, invasion and proliferation of colon cancer cells in vitro, and causes tumor growth and metastasis in mice.

Methods

By using yeast-two-hybrid assay, mass spectrometry, co-immunoprecipitation and peptide array we analyzed GIPC1 protein binding partners, by using the MACC1 gene promoter and chromatin immunoprecipitation and electrophoretic mobility shift assay we probed for GIPC1 as transcription factor. We employed GIPC1/MACC1-manipulated cell lines for in vitro and in vivo analyses, and we probed the GIPC1/MACC1 impact using human primary colorectal cancer (CRC) tissue.

Results

We identified MACC1 and its paralogue SH3BP4 as protein binding partners of the protein GIPC1, and we also demonstrated the binding of GIPC1 as transcription factor to the MACC1 promoter (TSS to -60 bp). GIPC1 knockdown reduced endogenous, but not CMV promoter-driven MACC1 expression, and diminished MACC1-induced cell migration and invasion. GIPC1 suppression reduced tumor growth and metastasis in mice intrasplenically transplanted with MACC1-overexpressing CRC cells. In human primary CRC specimens, GIPC1 correlates with MACC1 expression and is of prognostic value for metastasis formation and metastasis-free survival. Combination of MACC1 and GIPC1 expression improved patient survival prognosis, whereas SH3BP4 expression did not show any prognostic value.

Conclusions

We identified an important, dual function of GIPC1 - as protein interaction partner and as transcription factor of MACC1 - for tumor progression and cancer metastasis.

GIPC2 interacts with Fzd7 to promote prostate cancer metastasis by activating WNT signaling

Prostate cancer (PCa) causes significant mortality and morbidity, with advanced metastasis. WNT signaling is a promising therapeutic target for metastatic PCa. GIPC2 is a GIPC1 paralog involved in WNT signaling pathways associated with tumor progression, but its role in PCa metastasis remains unclear. Herein, we demonstrated that high GIPC2 expression in PCa tissues was significantly associated with distant metastasis and poor prognosis. Functional studies demonstrated that high GIPC2 expression due to CpG-island demethylation promoted increased metastatic capabilities of PCa cells. Conversely, silencing GIPC2 expression significantly inhibited PCa metastasis in vitro and in vivo. Furthermore, GIPC2 directly bound the WNT co-receptor Fzd7 through its PDZ domain, which enabled activation of WNT-β-catenin cascades, thereby stimulating PCa metastasis. Interestingly, GIPC2 protein was also identified as a component of exosomes and that it robustly stimulated PCa adhesion, invasion, and migration. The presence of GIPC2 in tumor-derived exosomes and ability to impact the behavior of tumor cells suggest that GIPC2 is a novel epigenetic oncogene involved in PCa metastasis. Our findings identified GIPC2 as a novel exosomal molecule associated with WNT signaling and may represent a potential therapeutic target and biomarker for metastatic PCa.

Neuropilin-1 (NRP-1)/GIPC1 pathway mediates glioma progression

Glioma occurs due to multi-gene abnormalities. Neuropilin-1 (NRP-1), as a transmembrane protein, involves in glioma proliferation, invasion, and migration, as well as tumor angiogenesis. The cytoplasmic protein, GAIP/RGS19-interacting protein (GIPC1), could regulate the clathrin-vesicles trafficking and recycling. Here, we show that NRP-1 co-localizes and co-immunoprecipitates with GIPC1, and the C-terminal SEA-COOH motif of NRP-1 interacts specially with the named from three proteins: PSD-95 (a 95 kDa protein involved in signaling at the post-synaptic density), DLG (the Drosophila melanogaster Discs Large protein) and ZO-1 (the zonula occludens 1 protein involved in maintenance of epithelial polarity) (PDZ) domain of GIPC1 in glioma cells. Knockdown of GIPC1 by small interfering RNA (siRNA) significantly reduces the proliferation and invasion of glioma cells in vitro and increases its apoptosis. Furthermore, si-GIPC1 prevents the action of adaptor proteins adaptor protein, phosphotyrosine interaction, PH domain and leucine zipper containing 1 (APPL1) and p130Cas and inhibits the downstream kirsten rat sarcoma viral oncogene homolog (KRAS)-ERK signaling pathway. This study demonstrated that NRP-1/GIPC1 pathway plays a vital role in glioma progression, and it is a potential important target for multi-gene combined therapeutics.

CAPG and GIPC1: Breast Cancer Biomarkers for Bone Metastasis Development and Treatment

Background:

Bone is the predominant site of metastasis from breast cancer, and recent trials have demonstrated that adjuvant bisphosphonate therapy can reduce bone metastasis development and improve survival. There is an unmet need for prognostic and predictive biomarkers so that therapy can be appropriately targeted.

Methods:

Potential biomarkers for bone metastasis were identified using proteomic comparison of bone-metastatic, lung-metastatic, and nonmetastatic variants of human breast cancer MDA-MB-231 cells. Clinical validation was performed using immunohistochemical staining of tumor tissue microarrays from patients in a large randomized trial of adjuvant zoledronic acid (zoledronate) (AZURE-ISRCTN79831382). We used Cox proportional hazards regression, the Kaplan-Meier estimate of the survival function, and the log-rank test to investigate associations between protein expression, clinical variables, and time to distant recurrence events. All statistical tests were two-sided.

Results:

Two novel biomarker candidates, macrophage-capping protein (CAPG) and PDZ domain–containing protein GIPC1 (GIPC1), were identified for clinical validation. Cox regression analysis of AZURE training and validation sets showed that control patients (no zoledronate) were more likely to develop first distant recurrence in bone (hazard ratio [HR] = 4.5, 95% confidence interval [CI] = 2.1 to 9.8, P < .001) and die (HR for overall survival = 1.8, 95% CI = 1.01 to 3.24, P = .045) if both proteins were highly expressed in the primary tumor. In patients with high expression of both proteins, zoledronate had a substantial effect, leading to 10-fold hazard ratio reduction (compared with control) for first distant recurrence in bone (P = .008).

Conclusions:

The composite biomarker, CAPG and GIPC1 in primary breast tumors, predicted disease outcomes and benefit from zoledronate and may facilitate patient selection for adjuvant bisphosphonate treatment.

Integrin traffic - the update

Integrins are a family of transmembrane cell surface molecules that constitute the principal adhesion receptors for the extracellular matrix (ECM) and are indispensable for the existence of multicellular organisms. In vertebrates, 24 different integrin heterodimers exist with differing substrate specificity and tissue expression. Integrin–extracellular-ligand interaction provides a physical anchor for the cell and triggers a vast array of intracellular signalling events that determine cell fate. Dynamic remodelling of adhesions, through rapid endocytic and exocytic trafficking of integrin receptors, is an important mechanism employed by cells to regulate integrin–ECM interactions, and thus cellular signalling, during processes such as cell migration, invasion and cytokinesis. The initial concept of integrin traffic as a means to translocate adhesion receptors within the cell has now been expanded with the growing appreciation that traffic is intimately linked to the cell signalling apparatus. Furthermore, endosomal pathways are emerging as crucial regulators of integrin stability and expression in cells. Thus, integrin traffic is relevant in a number of pathological conditions, especially in cancer. Nearly a decade ago we wrote a Commentary in Journal of Cell Science entitled ‘Integrin traffic’. With the advances in the field, we felt it would be appropriate to provide the growing number of researchers interested in integrin traffic with an update.

GAIP interacting protein C-terminus regulates autophagy and exosome biogenesis of pancreatic cancer through metabolic pathways

GAIP interacting protein C terminus (GIPC) is known to play an important role in a variety of physiological and disease states. In the present study, we have identified a novel role for GIPC as a master regulator of autophagy and the exocytotic pathways in cancer. We show that depletion of GIPC-induced autophagy in pancreatic cancer cells, as evident from the upregulation of the autophagy marker LC3II. We further report that GIPC regulates cellular trafficking pathways by modulating the secretion, biogenesis, and molecular composition of exosomes. We also identified the involvement of GIPC on metabolic stress pathways regulating autophagy and microvesicular shedding, and observed that GIPC status determines the loading of cellular cargo in the exosome. Furthermore, we have shown the overexpression of the drug resistance gene ABCG2 in exosomes from GIPC-depleted pancreatic cancer cells. We also demonstrated that depletion of GIPC from cancer cells sensitized them to gemcitabine treatment, an avenue that can be explored as a potential therapeutic strategy to overcome drug resistance in cancer.

Functional proteomics, human genetics and cancer biology of GIPC family members

GIPC1, GIPC2 and GIPC3 consist of GIPC homology 1 (GH1) domain, PDZ domain and GH2 domain. The regions around the GH1 and GH2 domains of GIPC1 are involved in dimerization and interaction with myosin VI (MYO6), respectively. The PDZ domain of GIPC1 is involved in interactions with transmembrane proteins [IGF1R, NTRK1, ADRB1, DRD2, TGFβR3 (transforming growth factorβ receptor type III), SDC4, SEMA4C, LRP1, NRP1, GLUT1, integrin α5 and VANGL2], cytosolic signaling regulators (APPL1 and RGS19) and viral proteins (HBc and HPV-18 E6). GIPC1 is an adaptor protein with dimerizing ability that loads PDZ ligands as cargoes for MYO6-dependent endosomal trafficking. GIPC1 is required for cell-surface expression of IGF1R and TGFβR3. GIPC1 is also required for integrin recycling during cell migration, angiogenesis and cytokinesis. On early endosomes, GIPC1 assembles receptor tyrosine kinases (RTKs) and APPL1 for activation of PI3K-AKT signaling, and G protein-coupled receptors (GPCRs) and RGS19 for attenuation of inhibitory Gα signaling. GIPC1 upregulation in breast, ovarian and pancreatic cancers promotes tumor proliferation and invasion, whereas GIPC1 downregulation in cervical cancer with human papillomavirus type 18 infection leads to resistance to cytostatic transforming growth factorβ signaling. GIPC2 is downregulated in acute lymphocytic leukemia owing to epigenetic silencing, while Gipc2 is upregulated in estrogen-induced mammary tumors. Somatic mutations of GIPC2 occur in malignant melanoma, and colorectal and ovarian cancers. Germ-line mutations of the GIPC3 or MYO6 gene cause nonsyndromic hearing loss. As GIPC proteins are involved in trafficking, signaling and recycling of RTKs, GPCRs, integrins and other transmembrane proteins, dysregulation of GIPCs results in human pathologies, such as cancer and hereditary deafness.

Immunohistochemical analysis of medullary breast carcinoma autoantigens in different histological types of breast carcinomas

BACKGROUND

On the past decade a plethora of investigations were directed on identification of molecules involved in breast tumorogenesis, which could represent a powerful tool for monitoring, diagnostics and treatment of this disease. In current study we analyzed six previously identified medullary breast carcinoma autoantigens including LGALS3BP, RAD50, FAM50A, RBPJ, PABPC4, LRRFIP1 with cancer restricted serological profile in different histological types of breast cancer.

METHODS

Semi-quantitative immunohistochemical analysis of 20 tissue samples including medullary breast carcinoma, invasive ductal carcinoma, invasive lobular carcinoma and non-cancerous tissues obtained from patients with fibrocystic disease (each of five) was performed using specifically generated polyclonal antibodies. Differences in expression patterns were evaluated considering percent of positively stained cells, insensitivity of staining and subcellular localization in cells of all tissue samples.

RESULTS

All 6 antigens predominantly expressed in the most cells of all histological types of breast tumors and non-cancerous tissues with slight differences in intensity of staining and subcellular localization. The most significant differences in expression pattern were revealed for RAD50 and LGALS3BP in different histological types of breast cancer and for PABPC4 and FAM50A antigens in immune cells infiltrating breast tumors.

CONCLUSIONS

This pilot study made possible to select 4 antigens LGALS3BP, RAD50, PABPC4, and FAM50A as promising candidates for more comprehensive research as potential molecular markers for breast cancer diagnostics and therapy.

VIRTUAL SLIDES

The virtual slides' for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1860649350796892.

Impact of the adaptor protein GIPC1/Synectin on radioresistance and survival after irradiation of prostate cancer

PURPOSE

Studies have shown that GIPC1/Synectin is an essential adaptor protein of receptors that play an important role in cancer progression and therapy resistance. This is the first study to explore the role of GIPC1/Synectin in radioresistance of prostate cancer and as a possible predictive marker for outcome of primary radiation therapy.

MATERIALS AND METHODS

The effect of RNA interference-mediated GIPC1/Synectin depletion on clonogenic cell survival after irradiation with 0, 2, 4, or 6 Gy was assayed in two different GIPC1/Synectin-expressing human prostate cancer cell lines. The clinical outcome data of 358 men who underwent radiotherapy of prostate cancer with a curative intention were analyzed retrospectively. Uni- and multivariate analysis was performed of prostate-specific antigen recurrence-free survival and overall survival in correlation with protein expression in pretreatment biopsy specimens. Protein expression was evaluated by standard immunohistochemistry methods.

RESULTS

In cell culture experiments, no change was detected in radiosensitivity after depletion of GIPC1/Synectin in GIPC1/Synectin-expressing prostate cancer cell lines. Furthermore, there was no correlation between GIPC1/Synectin expression in human pretreatment biopsy samples and overall or biochemical recurrence-free survival after radiotherapy in a retrospective analysis of the study cohort.

CONCLUSION

Our results do not show a predictive or prognostic function of GIPC1/Synectin expression for the outcome of radiotherapy in prostate cancer. Furthermore, our in vitro results do not support a role of GIPC1 in the cellular radiation response. However, the role of GIPC1 in the progression of prostate cancer and its precursors should be subject to further research.

Therapeutic implications of GIPC1 silencing in cancer

GIPC1 is a cytoplasmic scaffold protein that interacts with numerous receptor signaling complexes, and emerging evidence suggests that it plays a role in tumorigenesis. GIPC1 is highly expressed in a number of human malignancies, including breast, ovarian, gastric, and pancreatic cancers. Suppression of GIPC1 in human pancreatic cancer cells inhibits in vivo tumor growth in immunodeficient mice. To better understand GIPC1 function, we suppressed its expression in human breast and colorectal cancer cell lines and human mammary epithelial cells (HMECs) and assayed both gene expression and cellular phenotype. Suppression of GIPC1 promotes apoptosis in MCF-7, MDA-MD231, SKBR-3, SW480, and SW620 cells and impairs anchorage-independent colony formation of HMECs. These observations indicate GIPC1 plays an essential role in oncogenic transformation, and its expression is necessary for the survival of human breast and colorectal cancer cells. Additionally, a GIPC1 knock-down gene signature was used to interrogate publically available breast and ovarian cancer microarray datasets. This GIPC1 signature statistically correlates with a number of breast and ovarian cancer phenotypes and clinical outcomes, including patient survival. Taken together, these data indicate that GIPC1 inhibition may represent a new target for therapeutic development for the treatment of human cancers.

Autoantibodies to tumor-associated antigens in breast carcinoma

Autoantibodies (AAbs) to tumor-associated antigens (TAAs) have been identified in the circulation of patients with cancer. This paper will focus on recent knowledge related to circulating AAbs to TAAs in breast carcinoma. So far, the following TAAs have been identified to elicit circulating AAbs in breast carcinoma: p53, MUC-1, heat shock proteins (HSP-27, HSP-60, and HSP-90), HER2/neu/c-erb B2, GIPC-1, c-myc, c-myb, cancer-testis antigens (NY-ESO-1), BRCA1, BRCA2, endostatin, lipophilin B, cyclin B1, cyclin D1, fibulin, insulin-like growth factor binding protein 2 (IGFBP-2), topoisomerase II alpha (TOPO2α), and cathepsin D. Measurement of serum AAbs to one specific TAA only is of little value for screening and early diagnosis of breast carcinoma; however, assessment of AAbs to a panel of TAAs may have promising diagnostic potential.

Autoantibodies to tumor-associated antigens in epithelial ovarian carcinoma

This review will focus on recent knowledge related to circulating autoantibodies (AAbs) to tumor-associated antigens (TAAs) in epithelial ovarian carcinoma. So far, the following TAAs have been identified to elicit circulating AAbs in epithelial ovarian carcinoma: p53, homeobox proteins (HOXA7, HOXB7), heat shock proteins (HSP-27, HSP-90), cathepsin D, cancer-testis antigens (NY-ESO-1/LAGE-1), MUC1, GIPC-1, IL-8, Ep-CAM, and S100A7. Since AAbs to TAAs have been identified in the circulation of patients with early-stage cancer, it has been speculated that the assessment of a panel of AAbs specific for epithelial ovarian carcinoma TAAs might hold great potential as a novel tool for early diagnosis of epithelial ovarian carcinoma.