Novel oncoprotein EPS8: a new target for anticancer therapy

Loss of EPS8 sensitizes non-small-cell lung carcinoma to chemotherapy-induced DNA damage

Epidermal growth factor receptor pathway substrate number 8 (EPS8) has been reported to be critical in mediating tumor progression. However, the molecular and biological consequences of EPS8 overexpression remain unclear. Here we evaluated whether EPS8 increased DNA damage repair in non-small-cell lung carcinoma (NSCLC) cells and the mechanism of EPS8-mediated DNA damage repair which influenced chemosensitivity. Serial studies of functional experiments revealed that EPS8 knockdown inhibited cell growth, induced cell-cycle arrest and increased cisplatin therapeutic effects on NSCLC. EPS8 was found to induce DNA damage repair via upregulation of phosphorylated-ATM and downregulation of the tumor suppressor p53 and G1 cell kinase inhibitor p21. Moreover, in conjunction with cisplatin, decreasing EPS8 protein levels further increased p53 protein level and inhibited ATM signaling. Transplanted tumor studies were also performed to demonstrate that EPS8 knockdown inhibited tumor growth and sensitized tumors to cisplatin treatment. In conclusion, we have described a novel molecular mechanism through which EPS8 is likely to be involved in cancer progression and chemoresistance via DNA damage repair, indicating that EPS8 expression may influence the response to chemotherapy. Therefore, targeting EPS8 may be a potential therapeutic approach for patients with NSCLC.

EPS8L3 promotes pancreatic cancer proliferation and metastasis by activating GSK3B

Background

We intended to investigate the role and regulatory mechanism of EPS8L3 in increase the development of pancreatic cancer (PC).

Methods

In order to analyze the relationship between EPS8L3 level and clinicopathological indicators of PC patients, qRT-PCR was used to detect the expression of EPS8L3 in tumor specimens of 40 PC patients. EPS8L3 knockdown models were then constructed in PC cell lines. Furthermore, the effect of EPS8L3 on PC cell function was analyzed by CCK-8 and Transwell assay. Dual luciferase reporter gene assay and recovery assay were used to further investigate the underlying mechanism.

Results

qRT-PCR results indicated that EPS8L3 was highly expressed in PC tissues compared with adjacent ones. At the same time, the incidence of distant metastasis was higher in PC patients with high EPS8L3 level. In vitro analysis such as CCK-8 and Transwell experimentations indicated that knockdown of EPS8L3 markedly inhibited the proliferative and metastatic ability. Bio-informatics together with luciferase report assay proposing that EPS8L3 can target GSK3B. Western Blot results revealed that knockdown of EPS8L3 markedly reduced the GSK3B expression in PC cells, and there was a positively associated between the two in PC cells. In addition, the recovery experimentation proved that EPS8L3 and GSK3B have a mutual regulation effect. Overexpression of GSK3B can reversal the prohibitive effect of EPS8L3 knockdown on the malignant development of PC cells, thereby jointly regulating the occurrence and development of PC.

Conclusions

EPS8L3 promotes the development of PC by regulating GSK3B, suggesting that EPS8L3 can be used as a biomarker for early diagnosis and treatment of PC.

Dexmedetomidine suppresses the progression of esophageal cancer via miR-143-3p/epidermal growth factor receptor pathway substrate 8 axis

Esophageal cancer is one of the fatal cancers around the world. Dexmedetomidine (DEX) is widely used during anesthesia of esophageal cancer surgery. Nevertheless, the role of DEX in the progression of esophageal cancer remains barely known. The proliferation, apoptosis and metastasis of esophageal cancer cells were detected by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, flow cytometry, transwell migration and invasion assays and Western blot assay. The expression of miR-143-3p was measured by quantitative real-time PCR in esophageal cancer tissues and cells. The binding sites between miR-143-3p and epidermal growth factor receptor pathway substrate 8 (EPS8) were predicted by Starbase online software, and the combination was verified by dual-luciferase reporter assay. The murine xenograft model was established using KYSE150 cells to verify the function of DEX in vivo. DEX inhibited the proliferation and metastasis while accelerated the apoptosis of esophageal cancer cells. The abundance of miR-143-3p was lower in esophageal cancer tissues and cells than that in paring normal tissues and normal esophageal mucosal cells Het-1A. MiR-143-3p could be induced by DEX treatment in esophageal cancer cells, and miR-143-3p also suppressed the development of esophageal cancer. EPS8 was a functional target of miR-143-3p, and it played an oncogenic role in esophageal cancer. DEX inhibited the growth of tumor via miR-143-3p/EPS8 in vivo. DEX suppressed the growth and metastasis while facilitated the apoptosis of esophageal cancer cells through upregulating the abundance of miR-143-3p and reducing the level of EPS8 in vivo and in vitro, providing promising target for the treatment of esophageal cancer.

miR-345 inhibits migration and stem-like cell phenotype in gastric cancer via inactivation of Rac1 by targeting EPS8

Tumor metastasis is the main cause of treatment failure and death in patients with late stage of gastric cancer (GC). Studies showed that microRNAs (miRNAs) are important regulators in the process of tumor metastasis. In this study, we used miRNA array analysis to search for metastasis-associated miRNAs in primary and matched metastasis tissues of patients with GC and found that miR-345-5p (miR-345) was significantly higher in primary sites. Decreased expression of miR-345 was observed in GC tissues and cell lines, which was correlated with aggressive stage and grade. Patients with a higher level of miR-345 had a better prognosis. miR-345 could inhibit the migration and spheroid formation abilities in GC cell lines in transwell assay and spheroid formation assay. RNA sequencing and bioinformatics analysis revealed that miR-345 downregulated the epidermal growth factor receptor pathway substrate 8 (EPS8) and its downstream Rac1 signaling. Mechanistically, we confirmed that miR-345 could target EPS8 by directly binding to its 3' untranslated region by luciferase reporter assay. Further rescue assay showed that the ability of miR-345 in inhibiting the migration, stem-like cell phenotype, and epithelial-mesenchymal transition (EMT) in GC was partly dependent on targeting EPS8. In conclusion, miR-345 plays an inhibitory role in GC metastasis through inhibiting cell migration, EMT, and cancer stem cell phenotype via inactivation of Rac1 signaling by targeting EPS8, which provides the potential therapeutic and predictive value of miR-345 in GC.

Inhibitory short peptides targeting EPS8/ABI1/SOS1 tri-complex suppress invasion and metastasis of ovarian cancer cells

Background

We aimed to develop inhibitory short peptides that can prevent protein interactions of SOS1/EPS8/ABI1 tri-complex, a key component essential for ovarian cancer metastasis.

Methods

Plasmids containing various regions of HA-tagged ABI1 were co-transfected into ovarian cancer cells with Flag-tagged SOS1 or Myc-tagged EPS8. Co-immunoprecipitation and GST-pulldown assay were used to identify the regions of ABI1 responsible for SOS1 and EPS8 binding. Inhibitory short peptides of these binding regions were synthesized and modified with HIV-TAT sequence. The blocking effects of the peptides on ABI1-SOS1 or ABI1-EPS8 interactions in vitro and in vivo were determined by GST-pulldown assay. The capability of these short peptides in inhibiting invasion and metastasis of ovarian cancer cell was tested by Matrigel invasion assay and peritoneal metastatic colonization assay.

Results

The formation of endogenous SOS1/EPS8/ABI1 tri-complex was detected in the event of LPA-induced ovarian cancer cell invasion. In the tri-complex, ABI1 acted as a scaffold protein holding together SOS1 and EPS8. The SH3 and poly-proline+PxxDY regions of ABI1 were responsible for SOS1 and EPS8 binding, respectively. Inhibitory short peptides p + p-8 (ppppppppvdyedee) and SH3–3 (ekvvaiydytkdkddelsfmegaii) could block ABI1-SOS1 and ABI1-EPS8 interaction in vitro. TAT-p + p-8 peptide could disrupt ABI1-EPS8 interaction and suppress the invasion and metastasis of ovarian cancer cells in vivo.

Conclusions

TAT-p + p-8 peptide could efficiently disrupt the ABI1-EPS8 interaction, tri-complex formation, and block the invasion and metastasis of ovarian cancer cells.

Upregulation of EPS8L3 is associated with tumorigenesis and poor prognosis in patients with liver cancer

Epidermal growth factor receptor kinase substrate 8 (EPS8) plays critical roles in a variety of solid tumors. However, the biologic functions and clinical significance of EPS8‑like 3 (EPS8L3), an EPS8‑related protein, in liver cancer remain unclear. To measure EPS8L3 expression in liver cancer cell lines, reverse transcription‑quantitative PCR and western blot analyses were performed. The correlation between 338 patients with liver cancer and various clinicopathological factors obtained from the Oncomine database were evaluated using the χ2 test. Survival of patients with different expression of EPS8L3 was determined using Kaplan‑Meier survival analysis with a log rank test, and Cox regression analysis was performed to estimate the prognostic significance of EPS8L3 expression. Additionally, cell proliferation and migration were determined using Cell Counting Kit‑8 and wound healing assays. The results revealed that EPS8L3 expression was significantly upregulated in liver cancer tissues and cell lines (P<0.01), and that the expression of EPS8L3 was closely associated with grade (P=0.024) and mortality (P=0.011). Furthermore, survival analysis suggested patients with high EPS8L3 expression exhibited shorter survival compared with those with low EPS8L3 expression. Cox regression analysis indicated that EPS8L3 could be regarded as a prognostic biomarker in patients with liver cancer (hazard ratio, 1.58; 95% confidence interval, 1.085‑2.301; P=0.017). Additionally, in vitro assays revealed that EPS8L3 depletion significantly inhibited liver cancer cell proliferation and migration, and reduced the levels of phosphorylated PI3K and AKT in the PI3K/AKT signaling pathway. Collectively, the results of the present study, for the first time to the best of our knowledge, demonstrated that EPS8L3 serves as an oncogene in liver cancer development; therefore, EPS8L3 may be a valuable prognostic predictor for patients with liver cancer.

Hnrnpab regulates neural cell motility through transcription of Eps8

Cell migration requires a complicated network of structural and regulatory proteins. Changes in cellular motility can impact migration as a result of cell-type or developmental stage regulated expression of critical motility genes. Hnrnpab is a conserved RNA-binding protein found as two isoforms produced by alternative splicing. Its expression is enriched in the subventricular zone (SVZ) and the rostral migratory stream within the brain, suggesting possible support of the migration of neural progenitor cells in this region. Here we show that the migration of cells from the SVZ of developing Hnrnpab^-/- mouse brains is impaired. An RNA-seq analysis to identify Hnrnpab-dependent cell motility genes led us to Eps8, and in agreement with the change in cell motility, we show that Eps8 is decreased in Hnrnpab^-/- SVZ tissue. We scrutinized the motility of Hnrnpab^-/- cells and confirmed that the decreases in both cell motility and Eps8 are restored by ectopically coexpressing both alternatively spliced Hnrnpab isoforms, therefore these variants are surprisingly nonredundant for cell motility. Our results support a model where both Hnrnpab isoforms work in concert to regulate Eps8 transcription in the mouse SVZ to promote the normal migration of neural cells during CNS development.

A hypoxic signature marks tumors formed by disseminated tumor cells in the BALB-neuT mammary cancer model

Metastasis is the final stage of cancer progression. Some evidence indicates that tumor cell dissemination occurs early in the natural history of cancer progression. Disseminated tumor cells (DTC) have been described in the bone marrow (BM) of cancer patients as well as in experimental models, where they correlate with later development of metastasis. However, little is known about the tumorigenic features of DTC obtained at different time points along tumor progression. Here, we found that early DTC isolated from BM of 15-17 week-old Her2/neu transgenic (BALB-neuT) mice were not tumorigenic in immunodeficient mice. In contrast, DTC-derived tumors were easily detectable when late DTC obtained from 19-22 week-old BALB-neuT mice were injected. Angiogenesis, which contributes to regulate tumor dormancy, appeared dispensable to reactivate late DTC, although it accelerated growth of secondary DTC tumors. Compared with parental mammary tumors, gene expression profiling disclosed a distinctive transcriptional signature of late DTC tumors which was enriched for hypoxia-related transcripts and was maintained in ex-vivo cell culture. Altogether, these findings highlight a different tumorigenic potential of early and late DTC in the BALB-neuT model and describe a HIF-1α-related transcriptional signature in DTC tumors, which may render DTC angiogenesis-competent, when placed in a favourable environment.

A synthetic cell-penetrating peptide derived from nuclear localization signal of EPS8 exerts anticancer activity against acute myeloid leukemia

Background

Oncogenic roles of epidermal growth factor receptor pathway substrate no.8 (EPS8) have been widely reported in various tumors, making targeting of EPS8 an appealing prospect. Here, we describe the role of EPS8 in acute myeloid leukemia (AML) and consider the potential of EPS8 as an anti-AML target. Nuclear localization signal (NLS) residues of tumor-associated proteins are crucial for cell cycle progression, and specific inhibitors derived from the NLS have inhibitory effect on cancer cells. The NLS in EPS8 has potential as a specific anti-AML target.

Methods

Gene Expression Omnibus expression profiles of AML patients were used to test associations between EPS8 expression and AML patient outcome. The biological characteristics of AML cells after EPS8 knockdown were analyzed in vitro and in vivo. A specific peptide (CP-EPS8-NLS) derived from the NLS of EPS8 (amino acids 298–310) was synthesized, and the anti-AML effects of CP-EPS8-NLS were analyzed in cancer cells and in xenograft models. Mutated CP-EPS8-NLS and penetratin served as controls.

Results

We observed that elevated EPS8 expression in AML patients is associated with poor outcome. Knockdown of EPS8 significantly suppressed the survival of AML cells in vitro and in vivo. CP-EPS8-NLS interfered with EPS8-associated signaling and consequently exerted anti-AML activity. Importantly, CP-EPS8-NLS displayed anti-AML activity in various AML cell types, with diminished activity in PBMCs. CP-ESP8-NLS suppressed U937 cell proliferation, and injection of CP-EPS8-NLS exerted potent antitumor activity in the xenograft tumor models. A synergistic effect of CP-EPS8-NLS and chemotherapeutic agents was also observed in vitro and in vivo. Mechanistically, treatment of various AML cells with CP-EPS8-NLS downregulated the expression of EPS8 and its downstream pathways.

Conclusions

The function of CP-EPS8-NLS is explained by the presence of a NLS in EPS8, which has been shown to induce nuclear translocation, consequently resulting in EPS8 overexpression. These results indicate that EPS8 is a potential target for AML treatment.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0682-x) contains supplementary material, which is available to authorized users.

EPS8 regulates proliferation, apoptosis and chemosensitivity in BCR-ABL positive cells via the BCR-ABL/PI3K/AKT/mTOR pathway

Although the introduction of tyrosine kinase inhibitors greatly improved the survival of patients with chronic myeloid leukemia (CML), drug resistance remains a problem. Thus, mechanism-based novel therapeutic targets warrant exploration. Recently, epidermal growth factor receptor kinase substrate 8 (EPS8), which has been identified as an oncogene and plays an important role in a broad spectrum of solid tumours, was reported to be related to poor prognosis or chemoresistance in acute leukemia patients. However, its role in CML remains unclear. In the present study, using q-RT-PCR, we demonstrated that CML patients expressed a higher level of EPS8 mRNA in bone marrow mononuclear cells than healthy controls. Then, to determine the effect of EPS8 on the biological functions of CML cells, EPS8 expression was knocked down in the human CML cell line K562. Reduced proliferation, increased apoptosis, impaired adhesion and migration were observed in K562 cells after EPS8 silencing. Notably, attenuation of EPS8 increased chemosensitivity both in imatinib-sensitive K562 cells and in the imatinib-resistant murine BCR-ABL⁺ 32D-p210^{BCR/ABL-T315I} cells. Mechanistically, knockdown of EPS8 downregulated p-BCR/ABL and its downstream AKT/mTOR signalling pathway. Finally, knockdown of EPS8 attenuated K562 cell proliferation in BALB/c nude mice. These data indicated that EPS8 regulated the proliferation, apoptosis and chemosensitivity in BCR-ABL positive cells via the BCR-ABL/PI3K/AKT/mTOR pathway. Targeting EPS8 alone or combined with a tyrosine kinase inhibitor may be a promising alternative therapeutic strategy.

PTK6 Localized at the Plasma Membrane Promotes Cell Proliferation and MigratiOn Through Phosphorylation of Eps8

Protein tyrosine kinase 6 (PTK6; also known as Brk) is closely related to the Src family kinases, but lacks a membrane-targeting myristoylation signal. Sublocalization of PTK6 at the plasma membrane enhances its oncogenic potential. To understand the mechanism(s) underlying the oncogenic property of plasma---membrane-associated PTK6, proteins phosphorylated by membrane-targeted myristoylated PTK6 (Myr-PTK6) were enriched and analyzed using a proteomics approach. Eps8 which was identified by this method is phosphorylated by Myr-PTK6 in HEK293 cells. Mouse Eps8 expressed in HEK293 cells is phosphorylated by Myr-PTK6 at residues Tyr497, Tyr524, and Tyr534. Compared to wild-type Eps8 (Eps8 WT), the phosphorylation-defective 3YF mutant (Eps8 3YF) reverts the increased proliferation, migration, and phosphorylation of ERK and FAK mediated by Eps8 WT in HEK293 cells overexpressing PTK6. PTK6 knockdown in T-47D breast cancer cells decreased EGF-induced phosphorylation of Eps8. Endogenous PTK6 phosphorylates ectopically expressed Eps8 WT, but not Eps8 3YF mutant, in EGF-stimulated T-47D cells. The EGF-induced Eps8 phosphorylation enhances activation of ERK and FAK, cell adhesion, and anchorage-independent colony formation in T-47D cells, but not in the PTK6-knokdown T-47D cells. These results indicate that plasma-membrane-associated PTK6 phosphorylates Eps8, which promotes cell proliferation, adhesion, and migration and, thus, tumorigenesis. J. Cell. Biochem. 118: 2887-2895, 2017. © 2017 Wiley Periodicals, Inc.

Actin binding proteins in blood-testis barrier function

PURPOSE OF REVIEW

The present review examines the role of actin binding proteins (ABPs) on blood-testis barrier (BTB), an androgen-dependent ultrastructure in the testis, in particular their involvement on BTB remodeling during spermatogenesis.

RECENT FINDINGS

The BTB divides the seminiferous epithelium into the basal and the adluminal compartments. The BTB is constituted by coexisting actin-based tight junction, basal ectoplasmic specialization, and gap junction, and also intermediate filament-based desmosome between Sertoli cells near the basement membrane. Junctions at the BTB undergo continuous remodeling to facilitate the transport of preleptotene spermatocytes residing in the basal compartment across the immunological barrier during spermatogenesis. Thus, meiosis I/II and postmeiotic spermatid development take place in the adluminal compartment behind the BTB. BTB remodeling also regulates exchanges of biomolecules between the two compartments. As tight junction, basal ectoplasmic specialization, and gap junction use F-actin for attachment, actin microfilaments rapidly convert between their bundled and unbundled/branched configuration to confer BTB plasticity. The events of actin reorganization are regulated by two major classes of ABPs that convert actin microfilaments between their bundled and branched/unbundled configuration.

SUMMARY

We provide a model on how ABPs regulate BTB remodeling, shedding new light on unexplained male infertility, such as environmental toxicant-induced reproductive dysfunction since the testis, in particular the BTB, is sensitive to environmental toxicants, such as cadmium, bisphenol A, phthalates, and PFOS (perfluorooctanesulfonic acid or perfluorooctane sulfonate).

Identification of human leukemia antigen A*0201-restricted epitopes derived from epidermal growth factor pathway substrate number 8

T-cell-mediated immunotherapy of hematological malignancies requires selection of targeted tumor-associated antigens and T-cell epitopes contained in these tumor proteins. Epidermal growth factor receptor pathway substrate 8 (EPS8), whose function is pivotal for tumor proliferation, progression and metastasis, has been found to be overexpressed in most human tumor types, while its expression in normal tissue is low. The aim of the present study was to identify human leukemia antigen (HLA)-A*0201-restricted epitopes of EPS8 by using a reverse immunology approach. To achieve this, computer algorithms were used to predict HLA-A*0201 molecular binding, proteasome cleavage patterns as well as translocation of transporters associated with antigen processing. Candidate peptides were experimentally validated by T2 binding affinity assay and brefeldin-A decay assay. The functional avidity of peptide-specific cytotoxic T lymphocytes (CTLs) induced from peripheral blood mononuclear cells of healthy volunteers were evaluated by using an enzyme-linked immunosorbent spot assay and a cytotoxicity assay. Four peptides, designated as P455, P92, P276 and P360, had high affinity and stability of binding towards the HLA-A*0201 molecule, and specific CTLs induced by them significantly responded to the corresponding peptides and secreted IFN-γ. At the same time, the CTLs were able to specifically lyse EPS8-expressing cell lines in an HLA-A*0201-restricted manner. The present study demon-strated that P455, P92, P276 and P360 were CTL epitopes of EPS8, and were able to be used for epitope-defined adoptive T-cell transfer and multi-epitope-based vaccine design.

Re-positioning protein-kinase inhibitors against schistosomiasis

For decades, Praziquantel (PZQ) is the drug of choice against one of the most afflicting helminthic diseases worldwide, schistosomiasis. With respect to the fear of upcoming PZQ resistance, efforts are needed to find new chemotherapeutic options. Protein kinases (PKs) are essential molecules in signaling processes and indispensable to life. Aberrant PK functions take distinctive roles in human diseases and represent targets in chemotherapies. In schistosomes, conserved PKs were found to possess similar pivotal roles contributing not only to reproduction processes, but also to the pathology of schistosomiasis, which is closely associated to egg production. Exploiting the similarity of PKs of humans and schistosomes, PK inhibitors designed to treat human diseases may serve as lead compounds for new drugs against schistosomiasis.

Generation of cytotoxic T lymphocytes specific for native or modified peptides derived from the epidermal growth factor receptor pathway substrate 8 antigen

The ideal tumor antigen for the development of a cancer immunotherapy is one that is expressed only in tumor cells. The epidermal growth factor receptor pathway substrate 8 gene (Eps8) might be an effective antigen for cancer immunotherapy as it is overexpressed in a variety of cancer cells but not in normal tissues. In this study, the potential utility of an Eps8-derived immunotherapy was tested in vitro and in vivo. Three computer-based algorithms were used to design eight Eps8 native epitopes with potentially high binding affinity to the HLA-A2.1 molecule, which is found at a high frequency in the Chinese population. Of these eight, three peptides with a moderate affinity to the HLA-A2.1 molecule were modified at anchor residue positions to achieve stronger immunogenicity. These four modified peptides displayed stronger binding affinity to HLA-A2.1 molecules on T2 cells and a lower dissociation rate. In functional assays with human PBMCs in vitro and in HLA-A2.1/K(b) transgenic mice in vivo, CTLs primed by each native and modified peptide secreted IFN-γ and were toxic to cancer cells from a variety of tissue types in an HLA-A2.1-restricted and Eps8-specific manner. p101-109-2L and p276-284-1Y9V were superior to other modified and native epitopes both in vitro and in vivo. These results indicate that employing the native and modified epitopes identified here in Eps8-based immunotherapy for HLA-A2.1 positive cancer patients may result in efficient anticancer immune responses for diverse tumor types.

Eps8 regulates cellular proliferation and migration of breast cancer

The role of Eps8 in human breast cancer was studied, and we found that Eps8 was overexpressed in >60% of human breast cancer samples compared with adjacent normal breast tissues by immunohistochemical analysis. Eps8 was highly expressed in the highly invasive breast cancer cell line MDA-MB‑231 compared with the weakly invasive breast cancer cell lines MCF7 and MDA-MB‑468. MCF7 cell line stably expressing Eps8 was established by G418 screening, and the ectopic expression of Eps8 enhanced MCF7 breast cancer cell growth and survival as assessed by MTT analysis, cell viability and liquid colony formation, whereas the lentiviral expression of Eps8 shRNA in MDA-MB‑231 cells resulted in a significant reduction in cellular growth and proliferation in vitro and in vivo. Furthermore, Eps8 knockdown inhibited breast cancer cell migration in wound healing assays, decreased the number and size of EGF-induced filopodia and increased the sensitivity of breast cancer cells to cisplatin analyzed by MTT assays. Eps8 knockdown decreased the levels of phosphorylated extracellular signal-regulated protein kinase (ERK) and MMP9 but increased p53. Moreover, Eps8 knockdown suppressed a partial EMT-like transition and showed a significant increase in E-cadherin and decrease in N-cadherin and vimentin. These results suggest that Eps8 is overexpressed in human breast cancers, possibly by regulating ERK signaling, MMP9, p53 and EMT-like transition to affect breast cancer cell growth, migration and invasion. Therefore, Eps8 might represent a novel potential target in human breast cancer therapy.

Actin binding proteins, spermatid transport and spermiation

The transport of germ cells across the seminiferous epithelium is composed of a series of cellular events during the epithelial cycle essential to the completion of spermatogenesis. Without the timely transport of spermatids during spermiogenesis, spermatozoa that are transformed from step 19 spermatids in the rat testis fail to reach the luminal edge of the apical compartment and enter the tubule lumen at spermiation, thereby arriving the epididymis for further maturation. Step 19 spermatids and/or sperms that remain in the epithelium beyond stage VIII of the epithelial cycle will be removed by the Sertoli cell via phagocytosis to form phagosomes and be degraded by lysosomes, leading to subfertility and/or infertility. However, the biology of spermatid transport, in particular the final events that lead to spermiation remain elusive. Based on recent data in the field, we critically evaluate the biology of spermiation herein by focusing on the actin binding proteins (ABPs) that regulate the organization of actin microfilaments at the Sertoli-spermatid interface, which is crucial for spermatid transport during this event. The hypothesis we put forth herein also highlights some specific areas of research that can be pursued by investigators in the years to come.