Synuclein-gamma targeting peptide inhibitor that enhances sensitivity of breast cancer cells to antimicrotubule drugs

Synuclein Proteins in Cancer Development and Progression

Synucleins are a family of small, soluble proteins mainly expressed in neural tissue and in certain tumors. Since their discovery, tens of thousands of scientific reports have been published about this family of proteins as they are associated with severe human diseases. Although the physiological function of these proteins is still elusive, their relationship with neurodegeneration and cancer has been clearly described over the years. In this review, we summarize data connecting synucleins and cancer, going from the structural description of these molecules to their involvement in tumor-related processes, and discuss the putative use of these proteins as cancer molecular biomarkers.

The role of peptides in reversing chemoresistance of breast cancer: current facts and future prospects

Breast cancer is the first malignant tumor in women, and its incidence is also increasing year by year. Chemotherapy is one of the standard therapies for breast cancer, but the resistance of breast cancer cells to chemotherapy drugs is a huge challenge for the effective treatment of breast cancer. At present, in the study of reversing the drug resistance of solid tumors such as breast cancer, peptides have the advantages of high selectivity, high tissue penetration, and good biocompatibility. Some of the peptides that have been studied can overcome the resistance of tumor cells to chemotherapeutic drugs in the experiment, and effectively control the growth and metastasis of breast cancer cells. Here, we describe the mechanism of different peptides in reversing breast cancer resistance, including promoting cancer cell apoptosis; promoting non-apoptotic regulatory cell death of cancer cells; inhibiting the DNA repair mechanism of cancer cells; improving the tumor microenvironment; inhibiting drug efflux mechanism; and enhancing drug uptake. This review focuses on the different mechanisms of peptides in reversing breast cancer drug resistance, and these peptides are also expected to create clinical breakthroughs in promoting the therapeutic effect of chemotherapy drugs in breast cancer patients and improving the survival rate of patients.

Gamma-synuclein is a novel prognostic marker that promotes tumor cell migration in biliary tract carcinoma

Gamma‐synuclein (SNCG) promotes invasive behavior and is reportedly a prognostic factor in a range of cancers. However, its role in biliary tract carcinoma (BTC) remains unknown. Consequently, we investigated the clinicopathological significance and function of SNCG in BTC. Using resected BTC specimens from 147 patients with adenocarcinoma (extrahepatic cholangiocarcinoma [ECC, n = 96]; intrahepatic cholangiocarcinoma [ICC, n = 51]), we immunohistochemically evaluated SNCG expression and investigated its correlation with clinicopathological factors and outcomes. Furthermore, cell lines with high SNCG expression were selected from 16 BTC cell lines and these underwent cell proliferation and migration assays by siRNAs. In the results, SNCG expression was present in 22 of 96 (22.9%) ECC patients and in 10 of 51 (19.6%) ICC patients. SNCG expression was significantly correlated with poorly differentiated tumor in both ECC and ICC (p = 0.01 and 0.03, respectively) and with perineural invasion and lymph node metastases in ECC (p = 0.04 and 0.003, respectively). Multivariate analyses revealed that SNCG expression was an independent poor prognostic factor in both OS and RFS in both ECC and ICC. In vitro analyses showed high SNCG expression in three BTC cell lines (NCC‐BD1, NCC‐BD3, and NCC‐CC6‐1). Functional analysis revealed that SNCG silencing could suppress cell migration in NCC‐BD1 and NCC‐CC6‐1 and downregulate cell proliferation in NCC‐CC6‐1 significantly. In conclusion, SNCG may promote tumor cell activity and is potentially a novel prognostic marker in BTC.

A Novel Ruthenium-Fluvastatin Complex Downregulates SNCG Expression to Modulate Breast Carcinoma Cell Proliferation and Apoptosis via Activating the PI3K/Akt/mTOR/VEGF/MMP9 Pathway

Breast cancer is the most common cause of malignancy and cancer-related morbidity and death worldwide that requests effective and safe chemotherapy. Evaluation of metallodrug-based anticancer agents and statins as chemotherapeutics with fewer side effects is a largely unexplored research field. Synthesis and characterization of the ruthenium-fluvastatin complex were achieved using multiple spectroscopic techniques and thus further examined to evaluate its chemotherapeutic prospects in both MDA-MB-231 and MCF-7 cancer lines and eventually in vivo models of DMBA-induced mammary carcinogenesis in rodents. Our studies indicate that the metal and ligand chelation was materialized by the ligand's functional groups of carbonyl (=O) oxygen and hydroxyl (-OH), and the complex has been observed to be crystalline and able to chelate with CT-DNA. The complex was able to reduce cell proliferation and activate apoptotic events in breast carcinoma cell lines MCF-7 and MDA-MB-231. In addition, the complex was able to modify p53 expressions to interfere with apoptosis in the carcinoma of the breast, stimulated by the intrinsic apoptotic path assisted by Bcl2 and Bax in vivo, yet at the same point, controlling the PI3K/Akt/mTOR/VEGF pathway, as obtained from western blotting, correlates with the MMP9-regulated tumor mechanisms. Our research reveals that ruthenium-fluvastatin chemotherapy may disrupt, rescind, or interrupt breast carcinoma progression by modifying intrinsic apoptosis as well as the antiangiogenic cascade, thereby taking the role of a potential candidate in cancer therapy for the immediate future.

Suppression of synuclein gamma inhibits the movability of endometrial carcinoma cells by PI3K/AKT/ERK signaling pathway

BACKGROUND

Although overexpression of synuclein gamma (SNCG) has been reported in several cancers, few studies have been performed onSNCG in endometrial carcinomas.

OBJECTIVE

This study aimed to investigate the role of SNCG in the progression of endometrial carcinoma.

METHODS

The expression pattern and function ofSNCG gene were analyzed using the Gene Expression Omnibus (GEO) and Gene Set Enrichment Analysis (GSEA) datasets. Two vector types, containing either SNCG or negative control shRNAs, were used to evaluate cell proliferation, apoptosis, and metastasis using Cell Counting Kit 8, colony formation, flow cytometry, wound-healing, transwell, and invasion assays. The relative protein levels of N-cadherin, E-cadherin, vimentin, p-PI3K, PI3K, p-AKT, AKT, p-ERK, and ERK were determined by western bloting.

RESULTS

Our results revealed thatSNCG mRNA expression and SNCG protein levels in shRNA-treated SPEC2 cells were lower than in the negative control cells. Furthermore, cell proliferation, migration, and invasion were significantly inhibited in SNCG shRNA-treated cells, but apoptosis was increased. The results of western blot analysis indicated that SNCG silencing reduced the protein levels of N-cadherin, vimentin, p-PI3K, p-AKT, and p-ERK, but not those of total PI3K, AKT, and ERK.

CONCLUSIONS

Therefore, shRNA-mediated suppression of SNCG inhibited SPEC2 cell proliferation, migration, and invasion, and promoted SPEC2 cell apoptosis, which was presumably accomplished via regulation of the PI3K/AKT/ERK signaling pathway.

Synuclein gamma expression enhances radiation resistance of breast cancer cells

Resistance to therapy is a major obstacle for the effective treatment of cancer. Expression of synuclein-gamma (SNCG) has been associated with poor prognosis and resistance to therapy. While reports on SNCG overexpression contributing to chemoresistance exist, limited information is available on the relationship between SNCG and radioresistance of cancer cells. Here we investigated the role of SNCG in radiation resistance in breast cancer cells. siRNA mediated knockdown of SNCG (siSNCG) markedly reduced SNCG protein level compared to scrambled siRNA (siScr) treatment. Furthermore, siSNCG treatment sensitized Estrogen Receptor-positive breast cancer cells (MCF7 and T47D) to ionizing radiation at 4 to 12 Gy as evidenced by the significant increase of apoptotic or senescent cells and reduction in clonogenic cell survival in siSNCG treated cells compared to siScr treated cells. On the other hand, we established an in vitro model of SNCG ectopic expression by using a triple-negative breast cancer cell line (SUM159PT) to further investigate the radioprotective effect of SNCG. We showed that ectopic expression of SNCG significantly decreased apoptosis of SUM159PT cells and enhanced clonogenic cell survival after radiation treatment. At the molecular level, after irradiation, the p53 pathway was less activated when SNCG was present. Conversely, p21^Waf1/Cip1 expression was upregulated in SNCG-expressing cells. When p21 was down-regulated by siRNA, radiosensitivity of SNCG-expressing SUM159PT cells was dramatically increased. This suggested a possible connection between p21 and SNCG in radioresistance in these cells. In conclusion, our data provide for the first time experimental evidence for the role of SNCG in the radioresistance of breast cancer cells.

BCSG1 siRNA delivered by lentiviral vector suppressed proliferation and migration of MDA-MB-231 cells

Breast cancer-specific gene 1 (BCSG1), also referred to as γ-synuclein (SNCG), is highly expressed in human infiltrating breast carcinomas, but not in normal or benign breast tissue. The present study aimed to evaluate the effects of BCSG1 siRNA delivered by lentiviral vector on breast cancer cells and investigate the underlying mechanisms. BCSG1 RNAi lentiviral vector was constructed and transfected into MDA-MB-231 cells. BCSG1 mRNA levels were determined by quantitative polymerase chain reaction analysis. Cell proliferation, migration and apoptosis were evaluated by using the cell counting kit‑8, Transwell assay and flow cytometry, respectively, followed by western blotting to determine the relative levels of AKT, extracellular signal‑regulated kinase (ERK), p-AKT and p-ERK expression. BCSG1 mRNA levels were significantly reduced in MDA-MB‑231 cells following transfection of BCSG1 siRNA delivered by lentiviral vector. Cell migration and proliferation were significantly decreased and the cell cycle was arrested. Western blot analysis indicated that the protein levels of p-AKT and p-ERK were significantly lower in the BCSG1 siRNA-treated groups compared with the control and negative control groups. Therefore, BCSG1 siRNA delivered by lentiviral vector was able to significantly reduce BCSG1 expression, suppress cell migration and proliferation, possibly through the reduction of the protein levels of p-AKT and p-ERK.

Preparation of chitosan‑silicon dioxide/BCSG1‑siRNA nanoparticles to enhance therapeutic efficacy in breast cancer cells

Breast cancer is one of the most serious diseases, posing threats to women's physical and mental health. Gene therapy has been gradually regarded as an important part of tumor therapeutics. In the present study, the breast cancer‑specific gene 1‑small interference RNA (BCSG1‑siRNA) plasmid was designed, then encapsulated by chitosan‑silicon dioxide nanometer carriers. The results demonstrated a successful encapsulation of BCSG1‑siRNA in chitosan‑silicon dioxide nanoparticles (encapsulation efficiency exceeded 90%). BCSG1‑siRNA was released slowly (the release rate was almost 30% after 24 h). The cytotoxic effect on MCF‑7 cells was enhanced by increasing the concentration of nanoparticle (the proliferation rate was reduced to 13.4±5.3% and apoptosis rate was increased to 71.5±6.8%). Therefore, the materials presented in the current study acted as successful gene carriers and exhibited significant antitumor effects in breast cancer cells.

Synuclein-γ in uterine serous carcinoma impacts survival: An NRG Oncology/Gynecologic Oncology Group study

BACKGROUND

Synuclein-γ (SNCG) is highly expressed in advanced solid tumors, including uterine serous carcinoma (USC). The objective of the current study was to determine whether SNCG protein was associated with survival and clinical covariates using the largest existing collection of USCs from the Gynecologic Oncology Group (GOG-8023).

METHODS

High-density tissue microarrays (TMAs) of tumor tissues from 313 patients with USC were stained by immunohistochemistry for SNCG, p53, p16, FOLR1, pERK, pAKT, ER, PR, and HER2/neu. Associations of SNCG and other tumor markers with overall and progression-free survival were assessed using log-rank tests and Cox proportional-hazards models, which also were adjusted for age, race, and stage.

RESULTS

The overall survival at 5 years was 46% for women with high SNCG expression and 62% for those with low SNCG expression (log-rank P = .021; hazard ratio [HR], 1.31; 95% confidence interval [CI], 0.91-1.9 in adjusted Cox model). The progression-free survival rate at 5 years was worse for women who had high SNCG expression, at 40%, compared with 56% for those who had low SNCG expression (log-rank P = .0081; HR, 1.36; 95% CI, 0.96-1.92 in adjusted Cox model). High levels of both p53 and p16 were significantly associated with worse overall survival (p53: HR, 4.20 [95% CI, 1.54-11.45]; p16: HR, 1.95 [95% CI, 1.01-3.75]) and progression-free survival (p53: HR, 2.16 [95% CI, 1.09-4.27]; p16: HR, 1.53 [95% CI, 0.87-2.69]) compared with low levels.

CONCLUSIONS

This largest collection of USCs to date demonstrates that SNCG was associated with poor survival in univariate analyses. SNCG does not predict survival outcome independent of p53 and p16 in models that jointly consider multiple markers. Cancer 2017;123:1144-1155. © 2016 American Cancer Society.

Alternative splicing of synuclein gamma in endometrial cancer: identification of a novel isoform

Synuclein gamma (SNCG) is under consideration as a potential biomarker in cancer biology. Up to date four different SNCG variants are described. Due to growing evidence suggesting correlations between aberrant alternative splicing processes and cancer progression, we investigated the effects of peritumoural conditions on expression pattern of SNCG in endometrial cancer (EC) in vitro. Compared to breast cancer cell lines, mRNA expression levels of all known SNCG isoforms 1–4 are significantly reduced in EC cell lines. We identified a novel alternatively spliced variant of isoform 2 (isoform 2 short) which is found highly expressed in EC cell lines. Hypoxia and acidosis trigger an up-regulation of isoform 2 short. EC cell lines are characterized by low SNCG protein levels under control conditions, but exhibit a significant increase triggered by hypoxia and acidosis. In addition we analysed the potential association between SNCG protein expression and clinico-pathological parameters in human EC samples. Our findings indicate a grade-dependent induction of SNCG protein expression in endometrial cancer.

We identified for the first time a novel isoform of SNCG that is found specifically expressed in EC. Our results also strongly indicate the existence of a corresponding protein of isoform 2 short that potentially plays a critical role in EC cancer progression.

Overexpression of synuclein-γ predicts lack of benefit from radiotherapy for breast cancer patients

Background

Although radiotherapy following mastectomy was demonstrated to reduce the recurring risk and improve the prognosis of patients with breast cancer, it is also notorious for comprehensive side effects, hence only a selected group of patients can benefit. Therefore, the screening of molecular markers capable of predicting the efficacy of radiotherapy is essential.

Methods

We have established a cohort of 454 breast cancer cases and selected 238 patients with indications for postoperative radiotherapy. Synuclein-γ (SNCG) protein levels were assessed by immunohistochemistry, and SNCG status was retrospectively correlated with clinical features and survival in patients treated or not treated with radiotherapy. Gene Set Enrichment Analysis (GSEA) and survival analysis for online datasets were also performed for further validation.

Results

Among patients that received radiotherapy (82/238), those demonstrating positive SNCG expression had a 55.0 month shorter median overall survival (OS) in comparison to those demonstrating negative SNCG expression (78.4 vs. 133.4 months, log rank χ² = 16.13; p < 0.001). Among the patients that received no radiotherapy (156/238), SNCG status was not correlated with OS (log rank χ² = 2.40; p = 0.121). A COX proportional hazard analysis confirmed SNCG as an independent predictor of OS, only for patients who have received radiotherapy. Similar results were also obtained for distant metastasis-free survival (DMFS). A GSEA analysis indicated that SNCG was strongly associated with genes related to a radiation stress response. A survival analysis was performed with online databases consisting of breast cancer, lung cancer, and glioblastoma and further confirmed SNCG’s significance in predicting the survival of patients that have received radiotherapy.

Conclusion

A positive SNCG may serve as a potential marker to identify breast cancer patients who are less likely to benefit from radiotherapy and may also be extended to other types of cancer. However, the role of SNCG in radiotherapy response still needs to be further validated in randomized controlled trials prior to being exploited in clinical practice.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2750-y) contains supplementary material, which is available to authorized users.

Intracellular Dynamics of Synucleins: "Here, There and Everywhere"

Synucleins are small, soluble proteins expressed primarily in neural tissue and in certain tumors. The synuclein family consists of three members: α-, β-, and γ-synucleins present only in vertebrates. Members of the synuclein family have high sequence identity, especially in the N-terminal regions. The synuclein gene family came into the spotlight, when one of its members, α-synuclein, was found to be associated with Parkinson's disease and other neurodegenerative disorders, whereas γ-synuclein was linked to several forms of cancer. There are a lot of controversy and exciting debates concerning members of the synuclein family, including their normal functions, toxicity, role in pathology, transmission between cells and intracellular localization. Important findings which remain undisputable for many years are synuclein localization in synapses and their role in the regulation of synaptic vesicle trafficking, whereas their presence and function in mitochondria and nucleus is a debated topic. In this review, we present the data on the localization of synucleins in two intracellular organelles: the nucleus and mitochondria.

Combined expression of metastasis related markers Naa10p, SNCG and PRL-3 and its prognostic value in breast cancer patients

Combinations of multiple biomarkers representing distinct aspects of metastasis may have better prognostic value for breast cancer patients, especially those in late stages. In this study, we evaluated the protein levels of N-α-acetyltransferase 10 protein (Naa10p), synuclein-γ (SNCG), and phosphatase of regenerating liver-3 (PRL-3) in 365 patients with breast cancer by immunohistochemistry. Distinct prognostic subgroups of breast cancer were identified by combination of the three biomarkers. The Naa10p+SNCG-PRL-3- subgroup showed best prognosis with a median distant metastasis-free survival (DMFS) of 140 months, while the Naa10p-SNCG+PRL-3+ subgroup had the worst prognosis with a median DMFS of 60.5 months. Multivariate analysis indicated Naa10p, SNCG, PRL-3, and the TNM classification were all independent prognostic factors for both DMFS and overall survival (OS). The three biomarker combination of Naa10p, SNCG and PRL-3 performed better in patients with lymph node metastasis, especially those with more advanced tumors than other subgroups. In conclusion, the combined expression profile of Naa10p, SNCG and PRL-3, alone or in combination with the TNM classification system, may provide a precise estimate of prognosis of breast cancer patients.

siRNA-Mediated Suppression of Synuclein γ Inhibits MDA-MB-231 Cell Migration and Proliferation by Downregulating the Phosphorylation of AKT and ERK

Purpose

Synuclein-γ (SNCG), which was initially identified as breast cancer specific gene 1, is highly expressed in advanced breast cancers, but not in normal or benign breast tissue. This study aimed to evaluate the effects of SNCG siRNA-treatment on breast cancer cells and elucidate the associated mechanisms.

Methods

Vectors containing SNCG and negative control (NC) siRNAs were transfected into MDA-MB-231 cells; mRNA levels were determined by real-time polymerase chain reaction. Cell proliferation was evaluated using the MTT assay, cell migration was assessed by the Transwell assay, apoptosis and cell cycle analyses were conducted with the flow cytometer, and Western blot analysis was performed to determine the relative levels of AKT, ERK, p-AKT, and p-ERK expression.

Results

SNCG mRNA levels were significantly reduced in MDA-MB-231 cells transfected with SNCG siRNA. Our results indicate that in SNCG siRNA-treated cells, cell migration and proliferation decreased significantly, apoptosis was induced, and the cell cycle was arrested. Western blot analysis indicated that the protein levels of p-AKT and p-ERK were much lower in the SNCG siRNA-treated groups, than in the control and NC groups.

Conclusion

SNCG siRNA could decrease the migration and proliferation of breast cancer cells by downregulating the phosphorylation of AKT and ERK.

A peptide inhibitor of synuclein-γ reduces neovascularization of human endometriotic lesions

Endometriosis is a chronic painful gynecological condition characterized by adherence and growth of endometrium outside of the uterine cavity. Neovascularization is essential to the developing endometriosis lesion to support its growth. Synuclein-γ (SNCG), a protein implicated in cellular proliferation, is associated with a broad range of malignancies as well as endometriosis. We hypothesized that SNCG plays an important role in the neovascularization and growth of endometriosis and blocking of SNCG will interfere with survival of endometriotic lesions in a mouse model. We developed SP012, a novel 12 amino acid peptide inhibitor of SNCG. SP012 inhibited three-dimensional endothelial cell tube formation in a dose-dependent manner. Using intravital microscopy, SP012 was shown to be successfully delivered to human endometriotic lesions in a xenograft mouse model in vivo. Alymphoid (BALB/c-Rag2-/-Il2rγ-/- lacking T, B and NK cells) mice were surgically induced with human endometriotic lesions and treated with SP012 or phosphate-buffered saline control. SP012 treated endometriotic lesions had decreased growth, development and vascularization at the time of necroscopy. Endometriotic lesions treated with SP012 also had fewer isolectin (+) microvessels. These results, using a mouse model, indicate that SNCG plays a role in the neovascularization and subsequent growth of human endometriotic lesions. Targeting SNCG function using peptide inhibitor might provide a potential therapeutic option for the treatment of endometriosis in the future.

Investigation of intramolecular dynamics and conformations of α-, β- and γ-synuclein

The synucleins are a family of natively unstructured proteins consisting of α-, β-, and γ-synuclein which are primarily expressed in neurons. They have been linked to a wide variety of pathologies, including neurological disorders, such as Parkinson's disease (α-synuclein) and dementia with Lewy bodies (α- and β-synuclein), as well as various types of cancers (γ-synuclein). Self-association is a key pathological feature of many of these disorders, with α-synuclein having the highest propensity to form aggregates, while β-synuclein is the least prone. Here, we used a combination of fluorescence correlation spectroscopy and single molecule Förster resonance energy transfer to compare the intrinsic dynamics of different regions of all three synuclein proteins to investigate any correlation with putative functional or dysfunctional interactions. Despite a relatively high degree of sequence homology, we find that individual regions sample a broad range of diffusion coefficients, differing by almost a factor of four. At low pH, a condition that accelerates aggregation of α-synuclein, on average smaller diffusion coefficients are measured, supporting a hypothesis that slower intrachain dynamics may be correlated with self-association. Moreover, there is a surprising inverse correlation between dynamics and bulkiness of the segments. Aside from this observation, we could not discern any clear relationship between the physico-chemical properties of the constructs and their intrinsic dynamics. This work suggests that while protein dynamics may play a role in modulating self-association or interactions with other binding partners, other factors, particularly the local cellular environment, may be more important.

Clinical study of the relationship between γ-synuclein and the response of neoadjuvant chemotherapy in breast cancer

OBJECTIVES

To investigate relationships between several protein biomarkers and clinical responses to neoadjuvant chemotherapy (NAC) in breast cancer.

METHODS

Tumour tissue samples from female patients with locally advanced breast carcinoma (stages IIA to IIIC), treated with NAC regimens (including 5-fluorouracil, epirubicin, cyclophosphamide and docetaxel, epirubicin, cyclophosphamide) were analysed retrospectively. Immunohistochemical analysis was used to test for protein levels of oestrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor (HER)-2, protein 53 (p53) and γ-synuclein. Relationships between protein biomarkers and responses to NAC were analysed by multivariate logistic regression analysis.

RESULTS

Data from 154 patients (median age, 51 years; range 27-75 years) were included. Multivariate logistic regression analysis showed that γ-synuclein was an independent predictor of NAC objective response rate, and a statistically significant relationship was observed between NAC regimen, γ-synuclein levels and pathological complete response rate.

CONCLUSIONS

These study findings suggest that γ-synuclein - in combination with other markers such as ER, PR and HER-2 - may serve as a biomarker for response to NAC in breast cancer and warrants further study.

Synuclein-γ suppression mediated by RNA interference inhibits the clonogenicity and invasiveness of MCF-7 cells

The aim of the present study was to investigate the effects of synuclein-γ (SNCG) downregulation by RNA interference (RNAi) on the clonogenicity and invasiveness of MCF-7 breast cancer cells. This study used four pairs of SNCG-specific siRNAs which were designed and cloned into the pGPU6 plasmid for introduction into an MCF-7 cell line. The SNCG knockdown efficacies of the four siRNAs were compared using the reverse transcription polymerase chain reaction (RT-PCR) and immunocytochemistry. The cells' clonogenic and invasive phenotypes were examined with clonogenic and Boyden chamber assays. In comparison with the non-specific siRNA and empty vector controls, all four SNCG siRNAs were observed to significantly inhibit SNCG expression at the mRNA and protein levels (F=481.06, P<0.001; F=147.42, P<0.0001). SNCG suppression mediated by RNAi successfully inhibited the clonogenicity (P=0.002) and invasiveness (P<0.001) of transfected MCF-7 cells. According to the results of the present study, we concluded that SNCG suppression mediated by RNAi significantly suppressed SNCG expression at the mRNA and protein levels, suggesting that SNCG suppression mediated by an RNAi strategy may become a novel approach for treating advanced breast cancer.

Neural protein gamma-synuclein interacting with androgen receptor promotes human prostate cancer progression

Background

Gamma-synuclein (SNCG) has previously been demonstrated to be significantly correlated with metastatic malignancies; however, in-depth investigation of SNCG in prostate cancer is still lacking. In the present study, we evaluated the role of SNCG in prostate cancer progression and explored the underlying mechanisms.

Methods

First, alteration of SNCG expression in LNCaP cell line to test the ability of SNCG on cellular properties in vitro and vivo whenever exposing with androgen or not. Subsequently, the Dual-luciferase reporter assays were performed to evaluate whether the role of SNCG in LNCaP is through AR signaling. Last, the association between SNCG and prostate cancer progression was assessed immunohistochemically using a series of human prostate tissues.

Results

Silencing SNCG by siRNA in LNCaP cells contributes to the inhibition of cellular proliferation, the induction of cell-cycle arrest at the G1 phase, the suppression of cellular migration and invasion in vitro, as well as the decrease of tumor growth in vivo with the notable exception of castrated mice. Subsequently, mechanistic studies indicated that SNCG is a novel androgen receptor (AR) coactivator. It interacts with AR and promotes prostate cancer cellular growth and proliferation by activating AR transcription in an androgen-dependent manner. Finally, immunohistochemical analysis revealed that SNCG was almost undetectable in benign or androgen-independent tissues prostate lesions. The high expression of SNCG is correlated with peripheral and lymph node invasion.

Conclusions

Our data suggest that SNCG may serve as a biomarker for predicting human prostate cancer progression and metastasis. It also may become as a novel target for biomedical therapy in advanced prostate cancer.

Quantifying interactions of β-synuclein and γ-synuclein with model membranes

The synucleins are a family of proteins involved in numerous neurodegenerative pathologies [α-synuclein and β-synuclein (βS)], as well as in various types of cancers [γ-synuclein (γS)]. While the connection between α-synuclein and Parkinson's disease is well established, recent evidence links point mutants of βS to dementia with Lewy bodies. Overexpression of γS has been associated with enhanced metastasis and cancer drug resistance. Despite their prevalence in such a variety of diseases, the native functions of the synucleins remain unclear. They have a lipid-binding motif in their N-terminal region, which suggests interactions with biological membranes in vivo. In this study, we used fluorescence correlation spectroscopy to monitor the binding properties of βS and γS to model membranes and to determine the free energy of the interactions. Our results show that the interactions are most strongly affected by the presence of both anionic lipids and bilayer curvature, while membrane fluidity plays a very minor role. Quantifying the lipid-binding properties of βS and γS provides additional insights into the underlying factors governing the protein-membrane interactions. Such insights not only are relevant to the native functions of these proteins but also highlight their contributions to pathological conditions that are either mediated or characterized by perturbations of these interactions.

γ-Synuclein interacts with phospholipase Cβ2 to modulate G protein activation

Phospholipase Cβ2 (PLC β2) is activated by G proteins and generates calcium signals in cells. PLCβ2 is absent in normal breast tissue, but is highly expressed in breast tumors where its expression is correlated with the progression and migration of the tumor. This pattern of expression parallels the expression of the breast cancer specific gene protein 1 which is also known as γ-synuclein. The cellular function of γ-synuclein and the role it plays in proliferation are unknown. Here, we determined whether γ-synuclein can interact with PLCβ2 and affect its activity. Using co-immunprecitation and co-immunofluorescence, we find that in both benign and aggressive breast cancer cell lines γ-synuclein and PLCβ2 are associated. In solution, purified γ-synuclein binds to PLCβ2 with high affinity as measured by fluorescence methods. Protease digestion and mass spectrometry studies show that γ-synuclein binds to a site on the C-terminus of PLCβ2 that overlaps with the Gαq binding site. Additionally, γ-synuclein competes for Gαq association, but not for activators that bind to the N-terminus (i.e. Rac1 and Gβγ). Binding of γ-synuclein reduces the catalytic activity of PLCβ2 by mechanism that involves inhibition of product release without affecting membrane interactions. Since activated Gαq binds more strongly to PLCβ2 than γ-synuclein, addition of Gαq(GTPγS) to the γ-synuclein -PLCβ2 complex allows for relief of enzyme inhibition along with concomitant activation. We also find that Gβγ can reverse γ-synuclein inhibition without dissociating the γ-synuclein- PLCβ2- complex. These studies point to a role of γ-synuclein in promoting a more robust G protein activation of PLCβ2.

A novel calmodulin-β-PIX interaction and its implication in receptor tyrosine kinase regulation

Calmodulin (CaM), a ubiquitous calcium-binding protein, regulates numerous cellular processes, primarily in response to calcium flux. We have identified and characterized a novel interaction between CaM and β-p21-activated kinase interacting exchange factor (β-PIX), a putative guanine exchange factor implicated in cell signaling, using affinity pull-down assays, co-immunoprecipitation, co-localization and circular dichroism studies. Fluorescence-based titration and isothermal titration calorimetry experiments revealed a Ca(2+)-dependent binding mechanism (K(D)≤10μM). Further, we show that CaM participates in a multi-protein complex involving β-PIX and E3 ubiquitin ligase c-Cbl (casitas B-cell lymphoma), which may play a critical role in receptor tyrosine kinase regulation and downstream signaling.

Combined phenotype of 4 markers improves prognostic value of patients with colon cancer

INTRODUCTION

Combination of multiple biomarkers representing distinct aspects of tumor biology will have a better prognostic value. This study was to identify prognostic subgroups of colon adenocarcinoma by combined analysis of synuclein-gamma (SNCG), a human homologue of piwi (Hiwi), phosphatase of regenerating liver-3 (PRL-3), arrest-defective protein 1, homolog A (ARD1) and clinicopathologic features in 225 colon adenocarcinoma specimens.

METHODS

Immunohistochemistry for 4 tumor markers was performed in whole tissue sections from 225 colon adenocarcinoma patients with complete clinicopathologic data and up to 10-year follow-up. The immunohistochemical expression patterns were examined individually and in multimarker combinations. Univariate and multivariate analyses were performed to identify independent predictive markers of poor outcome.

RESULTS

With the tumor marker positive rate [32.0% (62/225) for SNCG; 76.9% (173/225) for combined SNCG/Hiwi/PRL-3/ARD1] and the detecting accuracy [61.9% (252/407) for SNCG; 82.6% (336/407) for combined SNCG/Hiwi/PRL-3/ARD1] increasing, incremental value of combined SNCG/Hiwi/PRL-3/ARD1 (P < 0.001; hazard ratios (HR), 3.2) to poor outcome was found. Stratified by lymph node, Hiwi alone (P = 0.004; HR, 3.2) led to poor outcome in patients without lymph node metastasis (LN-), and SNCG (P < 0.001; HR, 2.5) had independently poor prognostic value for patients with lymph node metastasis (LN+).

CONCLUSIONS

Multimarker phenotypes improved tumor positive rate, detecting accuracy and prognostic value. In addition, a subgroup of more aggressive tumors can be identified by evaluating Hiwi level in LN- cancer, and SNCG level in LN+ cancer.

Synuclein-γ (SNCG) protein expression is associated with poor outcome in endometrial adenocarcinoma

OBJECTIVE

Synuclein-γ (SNCG) is a marker for adverse and aggressive disease in breast cancer. In previous study, we found SNCG mRNA to be overexpressed in uterine serous carcinoma compared to uterine endometrioid adenocarcinoma. The aim of this study is to explore the prognostic value of SNCG in patients with endometrial cancer.

METHODS

279 endometrial cancer patients were retrieved from the archives. The tissue paraffin blocks were stained for SNCG antibody and its expression was correlated with clinicopathological prognostic factors.

RESULTS

There was a positive association between SNCG(+) immunoexpression and tumor grade, tumor stage, type II carcinomas, deep myometrial invasion and lymphovascular invasion. A correlation between SNCG(+) and adverse outcomes, such as shorter overall survival (OS) and disease free survival (DFS), was also detected. Following adjuvant therapy (radiation and chemotherapy or chemotherapy alone), we observed a difference in 5years DFS rate between SNCG(+) (41.6%) and SNCG(-) patients (59.5%).

CONCLUSION

Overexpression of SNCG seemed to be a predictor biomarker for aggressive tumor behavior and adverse outcome in patients with endometrial cancer. Future exploration of SNCG as a potential therapeutic target for selected patients could be of interest.

Novel molecular markers of malignancy in histologically normal and benign breast

To detect the molecular changes of malignancy in histologically normal breast (HNB) tissues, we recently developed a novel 117-gene-malignancy-signature. Here we report validation of our leading malignancy-risk-genes, topoisomerase-2-alpha (TOP2A), minichromosome-maintenance-protein-2 (MCM2) and “budding-uninhibited-by-benzimidazoles-1-homolog-beta” (BUB1B) at the protein level. Using our 117-gene malignancy-signature, we classified 18 fresh-frozen HNB tissues from 18 adult female breast cancer patients into HNB-tissues with low-grade (HNB-LGMA; N = 9) and high-grade molecular abnormality (HNB-HGMA; N = 9). Archival sections of additional HNB tissues from these patients, and invasive ductal carcinoma (IDC) tissues from six other patients were immunostained for these biomarkers. TOP2A/MCM2 expression was assessed as staining index (%) and BUB1B expression as H-scores (0–300). Increasing TOP2A, MCM2, and BUB1B protein expression from HNB-LGMA to HNB-HGMA tissues to IDCs validated our microarray-based molecular classification of HNB tissues by immunohistochemistry. We also demonstrated an increasing expression of TOP2A protein on an independent test set of HNB/benign/reductionmammoplasties, atypical-ductal-hyperplasia with and without synchronous breast cancer, DCIS and IDC tissues using a custom tissue microarray (TMA). In conclusion, TOP2A, MCM2, and BUB1B proteins are potential molecular biomarkers of malignancy in histologically normal and benign breast tissues. Larger-scale clinical validation studies are needed to further evaluate the clinical utility of these molecular biomarkers.

Evolution of structurally disordered proteins promotes neostructuralization

Protein structure is generally more conserved than sequence, but for regions that can adopt different structures in different environments, does this hold true? Understanding how structurally disordered regions evolve altered secondary structure element propensities as well as conformational flexibility among paralogs are fundamental questions for our understanding of protein structural evolution. We have investigated the evolutionary dynamics of structural disorder in protein families containing both orthologs and paralogs using phylogenetic tree reconstruction, protein structure disorder prediction, and secondary structure prediction in order to shed light upon these questions. Our results indicate that the extent and location of structurally disordered regions are not universally conserved. As structurally disordered regions often have high conformational flexibility, this is likely to have an effect on how protein structure evolves as spatially altered conformational flexibility can also change the secondary structure propensities for homologous regions in a protein family.

Synuclein gamma predicts poor clinical outcome in colon cancer with normal levels of carcinoembryonic antigen

Background

Synuclein gamma (SNCG), initially identified as a breast cancer specific gene, is aberrantly expressed in many different malignant tumors but rarely expressed in matched nonneoplastic adjacent tissues. In this study, we investigated the prognostic potential of SNCG in colon cancer particularly in the patients with normal carcinoembryonic antigen (CEA) levels.

Methods

SNCG levels were assessed immunohistochemically in cancer tissues from 229 colon adenocarcinoma patients with a mean follow-up of 44 months. Correlations between SNCG levels and clinicopathologic features, preoperative serum CEA level, and clinical outcome were analyzed statistically using SPSS.

Results

SNCG levels in colon adenocarcinoma were closely associated with intravascular embolus and tumor recurrence but independent of preoperative serum CEA levels. SNCG expression was an independent prognostic factor of a shorter disease-free survival (DFS) and overall survival (OS) (P < 0.0001). Multivariate analysis revealed that both tissue SNCG and serum CEA were independent prognostic factors of DFS (P = 0.001, <0.0001, respectively) for 170 patients with colon adenocarcinomas. Importantly, SNCG remained a prognostic determinant of DFS and OS (P = 0.001, 0.002) for 97 patients with normal preoperative serum CEA level.

Conclusions

Our results suggest for the first time that SNCG is a new independent predicator for poor prognosis in patients with colon adenocarcinoma, including those with normal CEA levels. Combination of CEA with SNCG improves prognostic evaluation for patients with colon adenocarcinoma.

Expression of γ-synuclein in colorectal cancer tissues and its role on colorectal cancer cell line HCT116

AIM: To investigate the expression pattern of γ-synuclein in colorectal cancer (CRC) tissues, and to study the effects of γ-synuclein on CRC cell line HCT116 biological features in vitro.

METHODS: The expression pattern of γ-synuclein was determined in 54 CRC tissues and 30 tumor-matched nonneoplastic adjacent tissues (NNAT) 5 cm away from the tumor via real-time quantitative reverse transcription PCR (RT-PCR) and immunohistochemistry. The relationship between γ-synuclein protein expression and clinicopathological factors of CRC tissues was analyzed. Three small interfering RNA (siRNA) targeting γ-synuclein mRNA plasmids were constructed and transfected into the CRC cell line HCT116. The stable cell lines were selected with G-418 for 28 d, and the biological features of these cells were examined by cell growth curve, soft agar assay, and cell migration and invasion assays in vitro.

RESULTS: The expression of γ-synuclein mRNA and protein was much higher in CRC tissue samples than in NNAT samples (P = 0.02, P = 0.036). There was a significant correlation between the γ-synuclein protein expression and clinical stage and lymph node involvement of CRC (P = 0.02, P = 0.033). In functional analysis we found that down-regulation of γ-synuclein expression in HCT116 cells could inhibit the growth, colony formation rate, and migration and invasion ability of HCT116 cells.

CONCLUSION: Increased expression of γ-synuclein in CRC tissues and the biological effects of reduced γ-synuclein expression on HCT116 cells suggest that γ-synuclein may play a positive role in the progression of CRC.

Friend or foe? Resolving the impact of glial responses in glaucoma

Glaucomatous vision loss results from the progressive degeneration of optic nerve axons and the death of retinal ganglion cells. This process is accompanied by dramatic alterations in the functional properties and distribution of glial cells in both the retina and the optic nerve head in a reaction commonly referred to as glial activation. The recent availability of rodent and cell culture glaucoma models has substantially contributed to our knowledge of glial activation under glaucomatous conditions. Conclusions drawn from these studies have led to the refinement of existing hypotheses and the generation of new ones. Because these hypotheses encompass both protective and injurious roles for glia, the impact of specific aspects of glial activation are current topics of intensive research, speculation, and debate in the field. With these unresolved issues in mind, this review will summarize recent progress in our understanding of the process of glial activation in the glaucomatous optic nerve head and retina.

Tumor cell-microenvironment interaction models coupled with clinical validation reveal CCL2 and SNCG as two predictors of colorectal cancer hepatic metastasis

PURPOSE

This study aimed to identify novel biological markers for the prediction of colorectal cancer liver metastasis.

EXPERIMENTAL DESIGN

We established two models that mimicked the interactions between colorectal tumor cells and the liver microenvironment. From these models we established subcell lines that had an enhanced ability to metastasize to the liver. Genes that related to hepatic metastasis were screened by microarray. The candidate markers were tested by immunohistochemistry, and their predictive accuracy was assessed by the cross-validation method and an independent test set.

RESULTS

Highly metastatic colon cancer cell sublines SW1116p21 and SW1116v3 were established from the tumor cell-microenvironment interaction models. Seven of the up-regulated genes in the sublines were selected as candidate markers for predicting metastatic potential. A total of 245 colorectal cancer samples were divided into a training set containing 117 cases and a test set containing 128 cases. In the training set, immunohistochemical analysis showed CCL2 and SNCG expression was higher in the hepatic metastasis group than in the nonmetastasis group, and was correlated with poor survival. Logistic regression analysis revealed that CCL2 and SNCG levels in primary tumors, serum carcinoembryonic antigen level, and lymph node metastasis status were the only significant (P < 0.05) parameters for detecting liver metastasis. In leave-one-out-cross-validation, the two markers, when combined with clinicopathologic features, resulted in 90.5% sensitivity and 90.7% specificity for hepatic metastasis detection. In an independent test set, the combination achieved 87.5% sensitivity and 82% specificity for predicting the future hepatic metastasis of colorectal cancer.

CONCLUSION

Our results suggest that these models are able to mimic the interactions between colorectal cancer cells and the liver microenvironment, and may represent a promising strategy to identify metastasis-related genes. CCL2 and SNCG, combined with clinicopathologic features, may be used as accurate predictors of liver metastasis in colorectal cancer.

Synuclein-gamma (SNCG) may be a novel prognostic biomarker in uterine papillary serous carcinoma

OBJECTIVES

SNCG in breast cancer is a marker for advanced and aggressive disease thereby correlating with a poor prognosis in patients. We set out to determine if SNCG expression in UPSC correlates with aggressive cellular properties, poor prognosis, and chemoresistance, and if silencing SNCG can reverse these attributes in vitro.

METHODS

A focused, real time PCR array was performed comparing a papillary serous (SPEC2) and an endometrioid (Ishikawa) endometrial cancer cell line. SNCG was the most differentially expressed gene. SNCG expression was confirmed by real time PCR, Western blot, and immunohistochemistry (IHC) and correlated with outcomes in a pilot set of 20 UPSC patients. A stably transfected SPEC2 cell line was created using shSNCG oligonucleotides. The effect of SNCG knockdown in SPEC2 cells on cell proliferation and sensitivity to paclitaxel-induced apoptosis was measured using a cell viability assay, BrdU incorporation assay, as well as cleaved PARP analyses.

RESULTS

SNCG mRNA as well as protein was highly expressed in SPEC2 cells while minimally to undetectable in several endometrioid endometrial cancer and normal endometrial cell lines. IHC also confirmed unique SNCG expression in UPSC tumors compared to low grade endometrial cancers. In UPSC patients, SNCG expression by IHC correlated with advanced stage and decreased progression-free survival. Knockdown of SNCG in SPEC2 cells caused a significant decrease in cell proliferation and increased sensitivity to paclitaxel-induced apoptosis.

CONCLUSIONS

SNCG is a novel biomarker for aggressive disease and chemoresistance in UPSC and merits further investigation both as a prognostic tool and as a therapeutic target.

A survey of the year 2007 literature on applications of isothermal titration calorimetry

Elucidation of the energetic principles of binding affinity and specificity is a central task in many branches of current sciences: biology, medicine, pharmacology, chemistry, material sciences, etc. In biomedical research, integral approaches combining structural information with in-solution biophysical data have proved to be a powerful way toward understanding the physical basis of vital cellular phenomena. Isothermal titration calorimetry (ITC) is a valuable experimental tool facilitating quantification of the thermodynamic parameters that characterize recognition processes involving biomacromolecules. The method provides access to all relevant thermodynamic information by performing a few experiments. In particular, ITC experiments allow to by-pass tedious and (rarely precise) procedures aimed at determining the changes in enthalpy and entropy upon binding by van't Hoff analysis. Notwithstanding limitations, ITC has now the reputation of being the "gold standard" and ITC data are widely used to validate theoretical predictions of thermodynamic parameters, as well as to benchmark the results of novel binding assays. In this paper, we discuss several publications from 2007 reporting ITC results. The focus is on applications in biologically oriented fields. We do not intend a comprehensive coverage of all newly accumulated information. Rather, we emphasize work which has captured our attention with originality and far-reaching analysis, or else has provided ideas for expanding the potential of the method.

Applications of novel monoclonal antibodies specific for synuclein-gamma in evaluating its levels in sera and cancer tissues from colorectal cancer patients

Overexpressions of synuclein-gamma (SNCG) in different cancers display stage-specific patterns. At present, appropriate anti-SNCG monoclonal antibodies (mAbs) with high specificity and affinity are unavailable for different immunoassays in clinical applications. In this study, we generated 10 mAbs against endogenous SNCG and evaluated SNCG levels in several colorectal cancer cell lines, serum samples and tumor tissues from colorectal cancer (CRC) patients. Elevated SNCG levels in cancer cell lines evaluated by a novel sandwich ELISA were consistent with data obtained from Western blot. Secreted SNCG protein levels in sera from CRC patients could be detected by the sandwich ELISA and were further confirmed by Western blot analysis following SNCG enrichment. Immunohistochemical results showed that SNCG was highly expressed in tumor cells of CRC patients, but was undetectable in the adjacent normal epithelium. Taken together, these novel anti-SNCG mAbs specifically recognized endogenous SNCG and were suitable for measuring SNCG levels in cell lysates, human serum samples, and tumor tissues. Elevated serum SNCG and overexpressed SNCG in tumor tissue from CRC patients suggest SNCG is a potential biomarker for CRC.

Hyaluronan-CD44 interaction activates stem cell marker Nanog, Stat-3-mediated MDR1 gene expression, and ankyrin-regulated multidrug efflux in breast and ovarian tumor cells

Hyaluronan (HA) is a major glycosaminoglycan in the extracellular matrix whose expression is tightly linked to multidrug resistance and tumor progression. In this study we investigated HA-induced interaction between CD44 (a HA receptor) and Nanog (an embryonic stem cell transcription factor) in both human breast tumor cells (MCF-7 cells) and human ovarian tumor cells (SK-OV-3.ipl cells). Using a specific primer pair to amplify Nanog by reverse transcriptase-PCR, we detected the expression of Nanog transcript in both tumor cell lines. In addition, our results reveal that HA binding to these tumor cells promotes Nanog protein association with CD44 followed by Nanog activation and the expression of pluripotent stem cell regulators (e.g. Rex1 and Sox2). Nanog also forms a complex with the "signal transducer and activator of transcription protein 3" (Stat-3) in the nucleus leading to Stat-3-specific transcriptional activation and multidrug transporter, MDR1 (P-glycoprotein) gene expression. Furthermore, we observed that HA-CD44 interaction induces ankyrin (a cytoskeletal protein) binding to MDR1 resulting in the efflux of chemotherapeutic drugs (e.g. doxorubicin and paclitaxel (Taxol)) and chemoresistance in these tumor cells. Overexpression of Nanog by transfecting tumor cells with Nanog cDNA stimulates Stat-3 transcriptional activation, MDR1 overexpression, and multidrug resistance. Down regulation of Nanog signaling or ankyrin function (by transfecting tumor cells with Nanog small interfering RNA or ankyrin repeat domain cDNA) not only blocks HA/CD44-mediated tumor cell behaviors but also enhances chemosensitivity. Taken together, these findings suggest that targeting HA/CD44-mediated Nanog-Stat-3 signaling pathways and ankyrin/cytoskeleton function may represent a novel approach to overcome chemotherapy resistance in some breast and ovarian tumor cells displaying stem cell marker properties during tumor progression.

Flexible nets: disorder and induced fit in the associations of p53 and 14-3-3 with their partners

Background

Proteins are involved in many interactions with other proteins leading to networks that regulate and control a wide variety of physiological processes. Some of these proteins, called hub proteins or hubs, bind to many different protein partners. Protein intrinsic disorder, via diversity arising from structural plasticity or flexibility, provide a means for hubs to associate with many partners (Dunker AK, Cortese MS, Romero P, Iakoucheva LM, Uversky VN: Flexible Nets: The roles of intrinsic disorder in protein interaction networks. FEBS J 2005, 272:5129-5148).

Results

Here we present a detailed examination of two divergent examples: 1) p53, which uses different disordered regions to bind to different partners and which also has several individual disordered regions that each bind to multiple partners, and 2) 14-3-3, which is a structured protein that associates with many different intrinsically disordered partners. For both examples, three-dimensional structures of multiple complexes reveal that the flexibility and plasticity of intrinsically disordered protein regions as well as induced-fit changes in the structured regions are both important for binding diversity.

Conclusions

These data support the conjecture that hub proteins often utilize intrinsic disorder to bind to multiple partners and provide detailed information about induced fit in structured regions.

Advances in γ-Synuclein and progression of tumors

γ-Synuclein with strong tissue specificity, a member of the synuclein family, is mainly located in nervous system. Recently, elevated levels of γ-Synuclein was detected in various types of cancers, such as breast, ovarian, liver, gastric cancers, etc., especially in their advanced stages, which indicated loss of tissue specificity in cancer development and also suggested that γ-Synuclein might serve as a new tumor marker. Additionally, multiple pathways influence the regulation of γ-Synuclein expression. γ-Synuclein has also been shown to promote invasion and metastasis of breast and ovarian cancers and enhance caners' tolerance to some chemotherapies . Overexpression of γ-synuclein also interferes with drug-induced apoptotic responses, which makes it a potential target for treatment.

Targeting synuclein-gamma to counteract drug resistance in cancer

BACKGROUND

Expression of synuclein-gamma (SNCG) protein is elevated in the advanced stages of many types of cancers, including ovarian, lung, liver, esophagus, colon, prostate and, in particular, breast. In breast carcinoma, SNCG is causatively linked to stimulated proliferation, metastasis and drug resistance.

OBJECTIVE

To establish SNCG as a potential therapeutic target and to discuss clinical use of SNCG inhibiting peptide.

METHODS

This review focuses on the plausible mechanisms of SNCG activity, SNCG mediated drug resistance and its inhibition.

RESULTS/CONCLUSION

Evidence based research shows that the aberrant expression of SNCG has a strong correlation with breast cancer progression and poor clinical outcome. A peptide based inhibitor counters activity of SNCG, which may be developed as an adjuvant therapy.

Taxanes, microtubules and chemoresistant breast cancer

The taxanes, paclitaxel and docetaxel are microtubule-stabilizing agents that function primarily by interfering with spindle microtubule dynamics causing cell cycle arrest and apoptosis. However, the mechanisms underlying their action have yet to be fully elucidated. These agents have become widely recognized as active chemotherapeutic agents in the treatment of metastatic breast cancer and early-stage breast cancer with benefits gained in terms of overall survival (OS) and disease-free survival (DFS). However, even with response to taxane treatment the time to progression (TTP) is relatively short, prolonging life for a matter of months, with studies showing that patients treated with taxanes eventually relapse. This review focuses on chemoresistance to taxane treatment particularly in relation to the spindle assembly checkpoint (SAC) and dysfunctional regulation of apoptotic signaling. Since spindle microtubules are the primary drug targets for taxanes, important SAC proteins such as MAD2, BUBR1, Synuclein-gamma and Aurora A have emerged as potentially important predictive markers of taxane resistance, as have specific checkpoint proteins such as BRCA1. Moreover, overexpression of the drug efflux pump MDR-1/P-gp, altered expression of microtubule-associated proteins (MAPs) including tau, stathmin and MAP4 may help to identify those patients who are most at risk of recurrence and those patients most likely to benefit from taxane treatment.