MUC1-C oncoprotein as a target in breast cancer: activation of signaling pathways and therapeutic approaches

Update on Mucin-1 immunotherapy in cancer: a clinical perspective

INTRODUCTION

Mucin 1 (MUC1) is particularly well suited as a cancer immunotherapy target due to the elevated protein expression and aberrant forms associated with malignancy. A variety of therapeutic strategies have been explored, including antibodies intended to induce cancer cell destruction, and vaccinations with peptides, tumor extracts, and gene expression systems.

AREAS COVERED

MUC1 immunotherapeutic strategies have included vaccination with peptide sequences, glycan molecules, viruses, and dendritic cells, monoclonal antibodies and monoclonal antibody conjugates. Here we review the relevant clinical trials in each field of immunotherapy with particular focus on large and recently published trials.

EXPERT OPINION

Long clinical experience in the trial setting has reduced concerns of immunotherapy associated toxicities and inappropriate immune responses, with the main limitation (common to many experimental approaches) being a lack of clinical efficacy. However, there have been sufficient treatment-associated responses to justify continued pursuit of MUC1 targeted immunotherapies. The focus now should be on application to the relevant cancers under appropriate circumstances and combination with the emerging non-specific immunotherapy approaches such as the PD-1 pathway inhibitors.

Aberrant activation of NF-κB signaling in mammary epithelium leads to abnormal growth and ductal carcinoma in situ

BACKGROUND

Approximately 1 in 5 women diagnosed with breast cancer are considered to have in situ disease, most often termed ductal carcinoma in situ (DCIS). Though recognized as a risk factor for the development of more invasive cancer, it remains unclear what factors contribute to DCIS development. It has been shown that inflammation contributes to the progression of a variety of tumor types, and nuclear factor kappa B (NF-κB) is recognized as a master-regulator of inflammatory signaling. However, the contributions of NF-κB signaling to tumor initiation are less well understood. Aberrant up-regulation of NF-κB activity, either systemically or locally within the breast, could occur due to a variety of commonly experienced stimuli such as acute infection, obesity, or psychological stress. In this study, we seek to determine if activation of NF-κB in mammary epithelium could play a role in the formation of hyperplastic ductal lesions.

METHODS

Our studies utilize a doxycycline-inducible transgenic mouse model in which constitutively active IKKβ is expressed specifically in mammary epithelium. All previously published models of NF-κB modulation in the virgin mammary gland have been constitutive models, with transgene or knock-out present throughout the life and development of the animal. For the first time, we will induce activation at later time points after normal ducts have formed, thus being able to determine if NF-κB activation can promote pre-malignant changes in previously normal mammary epithelium.

RESULTS

We found that even a short pulse of NF-κB activation could induce profound remodeling of mammary ductal structures. Short-term activation created hyperproliferative, enlarged ducts with filled lumens. Increased expression of inflammatory markers was concurrent with the down-regulation of hormone receptors and markers of epithelial differentiation. Furthermore, the oncoprotein mucin 1, known to be up-regulated in human and mouse DCIS, was over-expressed and mislocalized in the activated ductal tissue.

CONCLUSIONS

These results indicate that aberrant NF-κB activation within mammary epithelium can lead to molecular and morphological changes consistent with the earliest stages of breast cancer. Thus, inhibition of NF-κB signaling following acute inflammation or the initial signs of hyperplastic ductal growth could represent an important opportunity for breast cancer prevention.

Muc-1 promotes migration and invasion of oral squamous cell carcinoma cells via PI3K-Akt signaling

Muc-1 is a member of the carbohydrate-binding protein family that contributes to neoplastic transformation, tumor survival, angiogenesis, and metastasis. The aim of this study is to investigate the role of muc-1 in human oral squamous cell carcinoma progression. In this study, we tested our hypothesis that muc-1 regulate oral squamous cell carcinoma cells (SCC-9) malignant biological behaviors, and silencing muc-1 reduced SCC-9 cellular colony forming ability, migration and invasion. Moreover, silenced cells present defects in phosphatidylinositol 3-kinase (PI3K)-serine/threonine kinase (Akt) signaling, and reduced expression/activity of matrix metallopeptidase (MMP)-2/9. Furthermore, in muc-1 siRNA-transfected cells, we detected a decrease in signal transducer and activator of transcription 3 (STAT3) phosphorylation and nuclear translocation. In vivo, muc-1 siRNA cells inoculated subcutaneously in nude mice demonstrated decreased tumor growth and PI3K-Akt signaling inhibition. These results indicate that muc-1 is a key factor in SCC-9 tumor migration, invasion, and suggesting that muc-1 can be a novel therapeutic target in oral squamous cell carcinoma.

Pathobiological implications of mucin glycans in cancer: Sweet poison and novel targets

Mucins are large glycoproteins expressed on the epithelia that provide a protective barrier against harsh insults from toxins and pathogenic microbes. These glycoproteins are classified primarily as being secreted and membrane-bound; both forms are involved in pathophysiological functions including inflammation and cancer. The high molecular weight of mucins is attributed to their large polypeptide backbone that is extensively covered by glycan moieties that modulate the function of mucins and, hence, play an important role in physiological functions. Deregulation of glycosylation machinery during malignant transformation results in altered mucin glycosylation. This review describes the functional implications and pathobiological significance of altered mucin glycosylation in cancer. Further, this review delineates various factors such as glycosyltransferases and tumor microenvironment that contribute to dysregulation of mucin glycosylation during cancer. Finally, this review discusses the scope of mucin glycan epitopes as potential diagnostic and therapeutic targets.

Muc1 promotes migration and lung metastasis of melanoma cells

Early stages of melanoma can be successfully treated by surgical resection of the tumor, but there is still no effective treatment once it is progressed to metastatic phases. Although growing family of both melanoma metastasis promoting and metastasis suppressor genes have been reported be related to metastasis, the molecular mechanisms governing melanoma metastatic cascade are still not completely understood. Therefore, defining the molecules that govern melanoma metastasis may aid the development of more effective therapeutic strategies for combating melanoma. In the present study, we found that muc1 is involved in the metastasis of melanoma cells and demonstrated that muc1 disruption impairs melanoma cells migration and metastasis. The requirement of muc1 in the migration of melanoma cells was further confirmed by gene silencing in vitro. In corresponding to this result, over-expression of muc1 significantly promoted the migratory of melanoma cells. Moreover, down-regulation of muc1 expression strikingly inhibits melanoma cellular metastasis in vivo. Finally, we found that muc1 promotes melanoma migration through the protein kinase B (Akt) signaling pathway. To conclude, our findings suggest a novel mechanism underlying the metastasis of melanoma cells which might serve as a new intervention target for the treatment of melanoma.

Characterization of the MUC1-C Cytoplasmic Domain as a Cancer Target

Mucin 1 (MUC1) is a heterodimeric protein that is aberrantly expressed in diverse human carcinomas and certain hematologic malignancies. The oncogenic MUC1 transmembrane C-terminal subunit (MUC1-C) functions in part by transducing growth and survival signals from cell surface receptors. However, little is known about the structure of the MUC1-C cytoplasmic domain as a potential drug target. Using methods for structural predictions, our results indicate that a highly conserved CQCRRK sequence, which is adjacent to the cell membrane, forms a small pocket that exposes the two cysteine residues for forming disulfide bonds. By contrast, the remainder of the MUC1-C cytoplasmic domain has no apparent structure, consistent with an intrinsically disordered protein. Our studies thus focused on targeting the MUC1 CQCRRK region. The results show that L- and D-amino acid CQCRRK-containing peptides bind directly to the CQC motif. We further show that the D-amino acid peptide, designated GO-203, blocks homodimerization of the MUC1-C cytoplasmic domain in vitro and in transfected cells. Moreover, GO-203 binds directly to endogenous MUC1-C in breast and lung cancer cells. Colocalization studies further demonstrate that GO-203 predominantly binds to MUC1-C at the cell membrane. These findings support the further development of agents that target the MUC1-C cytoplasmic domain CQC motif and thereby MUC1-C function in cancer cells.

MUC1-C confers EMT and KRAS independence in mutant KRAS lung cancer cells

Non-small cell lung cancers (NSCLCs) that harbor an oncogenic KRAS mutation are often associated with resistance to targeted therapies. The MUC1-C transmembrane protein is aberrantly overexpressed in NSCLCs and confers a poor outcome; however, the functional role for MUC1-C in mutant KRAS NSCLC cells has remained unclear. The present studies demonstrate that silencing MUC1-C in A549/KRAS(G12S) and H460/KRAS(Q61H) NSCLC cells is associated with downregulation of AKT signaling and inhibition of growth. Overexpression of a MUC1-C(CQC→AQA) mutant, which inhibits MUC1-C homodimerization and function, suppressed both AKT and MEK activation. Moreover, treatment with GO-203, an inhibitor of MUC1-C homodimerization, blocked AKT and MEK signaling and decreased cell survival. The results further demonstrate that targeting MUC1-C suppresses expression of the ZEB1 transcriptional repressor by an AKT-mediated mechanism, and in turn induces miR-200c. In concert with these effects on the ZEB1/miR-200c regulatory loop, targeting MUC1-C was associated with reversal of the epithelial-mesenchymal transition (EMT) and inhibition of self-renewal capacity. Loss of MUC1-C function also attenuated KRAS independence and inhibited growth of KRAS mutant NSCLC cells as tumors in mice. These findings support a model in which targeting MUC1-C inhibits mutant KRAS signaling in NSCLC cells and thereby reverses the EMT phenotype and decreases self-renewal.

Mucin1 promotes the migration and invasion of hepatocellular carcinoma cells via JNK-mediated phosphorylation of Smad2 at the C-terminal and linker regions

Mucin1 (MUC1), as an oncogene, plays a key role in the progression and tumorigenesis of many human adenocarcinomas. In this study, wound-healing, transwell migration and matrigel invasion assays showed that MUC1 promotes human hepatocellular carcinoma (HCC) cell migration and invasion by MUC1 gene silencing and overexpressing. Treatment with exogenous transforming growth factor beta (TGF-β)1, TGF-β type I receptor (TβRI) inhibitor, TGF-β1 siRNAs, or activator protein 1 (AP-1) inhibitor to MUC1-overexpressing HCC cells revealed that MUC1-induced autocrine TGF-β via JNK/AP-1 pathway promotes the cell migration and invasion. In addition, the migration and invasion of HCC cells were more significantly inhibited by JNK inhibitor compared with that by TβRI inhibitor or TGF-β1 siRNAs. Further studies demonstrated that MUC1-mediated JNK activation not only enhances the phosphorylation of Smad2 C-terminal at Ser-465/467 site (Smad2C) through TGF-β/TβRI, but also directly enhances the phosphorylation of Smad2 linker region at Ser-245/250/255 site (Smad2L), and then both of them collaborate to upregulate matrix metalloproteinase (MMP)-9-mediated cell migration and invasion of HCC. These results indicate that MUC1 is an attractive target in liver cancer therapy.

Loss of Core 1-derived O-Glycans Decreases Breast Cancer Development in Mice

Mucin-type core 1-derived O-glycans, one of the major types of O-glycans, are highly expressed in mammary gland epithelium. Abnormal O-glycans such as Tn antigen are found in over 90% of breast cancers; however, the in vivo role of these aberrant O-glycans in the etiology of breast cancer is unclear. We generated mice with mammary epithelial specific deletion of core 1-derived O-glycans. By crossing with two spontaneous mouse breast cancer models, we determined that loss of core 1-derived O-glycans delays the onset and progression of breast cancer development. Deficiency of core 1 O-glycosylation impaired the localization of Muc1, a major O-glycoprotein, on the apical surfaces of mammary epithelium. Signaling mediated by Muc1, which is critical for breast cancer development, was also defective in the absence of core 1 O-glycans. This study reveals an unexpected role of core 1-derived O-glycans in breast cancer development in mice.

The combined treatment with novel platinum(II) complex and anti-MUC1 increases apoptotic response in MDA-MB-231 breast cancer cells

New strategy of cancer’s targeting treatment is combining monoclonal antibodies with chemotherapeutic agents. An important goal of targeted therapy appears to be a transmembrane glycoprotein type I—mucin 1 (MUC1), which is overexpressed in tumors of epithelial origin, especially in breast cancer. The goal of the study was to check the effect of monoclonal antibody against MUC1 with novel platinum(II) complex (Pt12) on selected aspects of apoptosis in human MDA-MB-231 breast cancer cells. The number of apoptotic and necrotic cells was measured using annexin V binding assay. The decrease of mitochondrial membrane potential (MMP) and DNA fragmentation was analyzed. Finally, the influence of novel platinum(II) complex (Pt12) used with anti-MUC1 on the concentration of selected markers of apoptosis such as Bax, caspase-8, -9, and caspase-3 was performed using ELISA. The results from combined treatment were compared with those obtained using monotherapy. In our study, we proved that anti-MUC1 used in combination with Pt12 strongly induced apoptosis in MDA-MB-231 breast cancer cell line. The effect was stronger than treatment with Pt12, cisplatin, anti-MUC1, and anti-MUC1 used with cisplatin. We also observed the highest decrease of MMP and the strongest DNA fragmentation after such a combined treatment. The results obtained from ELISA showed increased concentration of Bax, caspases-8, -9, -3 compared to monotherapy. Our study proved that Pt12 together with anti-MUC1 strongly induced apoptosis in estrogen-negative breast cancer cell line (MDA-MB-231). The apoptosis may go through extrinsic pathway associated with caspase-8 as well as intrinsic pathway connected with caspase-9.

Oncogenic CXCL10 signalling drives metastasis development and poor clinical outcome

Background:

The CXCL10/CXCR3 signalling mediates paracrine interactions between tumour and stromal cells that govern leukocyte trafficking and angiogenesis. Emerging data implicate noncanonical CXCL10/CXCR3 signalling in tumourigenesis and metastasis. However, little is known regarding the role for autocrine CXCL10/CXCR3 signalling in regulating the metastatic potential of individual tumour clones.

Methods:

We performed transcriptomic and cytokine profiling to characterise the functions of CXCL10 and CXCR3 in tumour cells with different metastatic abilities. We modulated the expression of the CXCL10/CXCR3 pathway using shRNA-mediated silencing in both in vitro and in vivo models of B16F1 melanoma. In addition, we examined the expression of CXCL10 and CXCR3 and their associations with clinical outcomes in clinical data sets derived from over 670 patients with melanoma and colon and renal cell carcinomas.

Results:

We identified a critical role for autocrine CXCL10/CXCR3 signalling in promoting tumour cell growth, motility and metastasis. Analysis of publicly available clinical data sets demonstrated that coexpression of CXCL10 and CXCR3 predicted an increased metastatic potential and was associated with early metastatic disease progression and poor overall survival.

Conclusion:

These findings support the potential for CXCL10/CXCR3 coexpression as a predictor of metastatic recurrence and point towards a role for targeting of this oncogenic axis in the treatment of metastatic disease.

Micro-RNAs miR-29a and miR-330-5p function as tumor suppressors by targeting the MUC1 mucin in pancreatic cancer cells

MUC1 is an oncogenic mucin overexpressed in several epithelial cancers, including pancreatic ductal adenocarcinoma, and is considered as a potent target for cancer therapy. To control cancer progression, miRNAs became very recently, major targets and tools to inhibit oncogene expression. Inhibiting MUC1 using miRNAs appears thus as an attractive strategy to reduce cancer progression. However, potent miRNAs and associated mechanisms regulating MUC1 expression remain to be identified. To this aim, we undertook to study MUC1 regulation by miRNAs in pancreatic cancer cells and identify those with tumor suppressive activity. MiRNAs potentially targeting the 3'-UTR, the coding region, or the 5'-UTR of MUC1 were selected using an in silico approach. Our in vitro and in vivo experiments indicate that miR-29a and miR-330-5p are strong inhibitors of MUC1 expression in pancreatic cancer cells through direct binding to MUC1 3'-UTR. MUC1 regulation by the other selected miRNAs (miR-183, miR-200a, miR-876-3p and miR-939) was found to be indirect. MiR-29a and miR-330-5p are also deregulated in human pancreatic cancer cell lines and tissues and in pancreatic tissues of Kras(G12D) mice. In vitro, miR-29a and miR-330-5p inhibit cell proliferation, cell migration, cell invasion and sensitize pancreatic cancer cells to gemcitabine. In vivo intra-tumoral injection of these two miRNAs in xenografted pancreatic tumors led to reduced tumor growth. Altogether, we have identified miR-29a and miR-330-5p as two new tumor suppressive miRNAs that inhibit the expression of MUC1 oncogenic mucin in pancreatic cancer cells.

Combination of curcumin and bicalutamide enhanced the growth inhibition of androgen-independent prostate cancer cells through SAPK/JNK and MEK/ERK1/2-mediated targeting NF-κB/p65 and MUC1-C

Background

Prostate cancer is one of the most common malignancies in men. The mucin 1 (MUC1) heterodimeric oncoprotein is overexpressed in human prostate cancers with aggressive pathologic and clinical features, resulting in a poor outcome. However, the functional role for MUC1 C-terminal domain (MUC1-C) in androgen-independent prostate cancer occurrence and development has remained unclear.

Methods

Cell viability was measured by MTT assays. Western blot analysis was performed to measure the phosphorylation and protein expression of SAPK/JNK and ERK1/2, and MUC1-C, NF-κB subunit p65 and p50. Exogenous expression of MUC1-C, NF-κB subunit p65 was carried out by transient and electroporated transfection assays.

Results

We showed that curcumin inhibited the growth of androgen-independent prostate cancer cells and a synergy was observed in the presence of curcumin and bicalutamide, the androgen receptor antagonist. To further explore the potential mechanism underlining this, we found that curcumin increased the phosphorylation of ERK1/2 and SAPK/JNK, which was enhanced by bicalutamide. In addition, curcumin reduced the protein expression of MUC1-C and NF-κB subunit p65, which were abrogated in the presence of the inhibitors of MEK/ERK1/2 (PD98059) and SAPK/JNK (SP60015). A further reduction was observed in the combination of curcumin with bicalutamide. Moreover, while exogenous expression of MUC1-C had little effect on curcumin-reduced p65, the overexpression of p65 reversed the effect of curcumin on MUC1-C protein expression suggesting that p65 is upstream of MUC1-C. Intriguingly, we showed that exogenous expression of MUC1-C feedback diminished the effect of curcumin on phosphorylation of ERK1/2 and SAPK/JNK, and antagonized the effect of curcumin on cell growth.

Conclusion

Our results show that curcumin inhibits the growth of androgen-independent prostate cancer cells through ERK1/2- and SAPK/JNK-mediated inhibition of p65, followed by reducing expression of MUC1-C protein. More importantly, there are synergistic effects of curcumin and bicalutamide. The negative feedback regulatory loop of MUC1-C to ERK1/2 and SAPK/JNK further demonstrates the role of MUC1-C that contributes to the overall responses of curcumin. This study unveils the potential molecular mechanism by which combination of curcumin with bicalutamide enhances the growth inhibition of androgen-independent prostate cancer cells.

Targeted nanoparticles for image-guided treatment of triple-negative breast cancer: clinical significance and technological advances

Effective treatment of triple-negative breast cancer (TNBC) with its aggressive tumor biology, highly heterogeneous tumor cells, and poor prognosis requires an integrated therapeutic approach that addresses critical issues in cancer therapy. Multifunctional nanoparticles with the abilities of targeted drug delivery and noninvasive imaging for monitoring drug delivery and responses to therapy, such as theranostic nanoparticles, hold great promise toward the development of novel therapeutic approaches for the treatment of TNBC using a single therapeutic platform. The biological and pathological characteristics of TNBC provide insight into several potential molecular targets for current and future nanoparticle-based therapeutics. Extensive tumor stroma, highly proliferative cells, and a high rate of drug resistance are all barriers that must be appropriately addressed in order for these nanotherapeutic platforms to be effective. Utilization of the enhanced permeability and retention effect coupled with active targeting of cell surface receptors expressed by TNBC cells, and tumor-associated endothelial cells, stromal fibroblasts, and macrophages is likely to overcome such barriers to facilitate more effective drug delivery. An in-depth summary of current studies investigating targeted nanoparticles in preclinical TNBC mouse and human xenograft models is presented. This review aims to outline the current status of nanotherapeutic options for TNBC patients, identification of promising molecular targets, challenges associated with the development of targeted nanotherapeutics, the research done by our group as well as by others, and future perspectives on the nanomedicine field and ways to translate current preclinical studies into the clinic.

Autophagy is decreased in triple-negative breast carcinoma involving likely the MUC1-EGFR-NEU1 signalling pathway

Triple-negative breast carcinoma (TN) is a heterogeneous cancer type expressing EGFR in 75% of cases. MUC1 is a large type I sialylated glycoprotein comprising two subunits (α and β chains, also called respectively MUC1-VNTR and MUC1-CT), which was found to regulate EGFR activity through endocytic internalisation. Endocytosis and autophagy use the lysosome pathway involving NEU1. Recently, a molecular EGFR-MUC1-NEU1 complex was suggested to play a role in EGFR pathway. In the aim to understand the relationship between EGFR-MUC1-NEU1 complex and autophagy in breast carcinoma, we compared triple negative (TN) showing a high-EGFR expression with luminal (LUM) presenting low-EGFR level. We studied the expression of MUC1-VNTR, MUC1-CT and NEU1 in comparison with those of two molecular actors of autophagy, PI3K (p110β) and Beclin1. A total of 87 breast cancers were split in two groups following the immunohistochemical classification of breast carcinoma: 48 TN and 39 LUM. Our results showed that TN presented a high expression of EGFR and a low expression of MUC1-VNTR, MUC1-CT, NEU1, Beclin-1 and PI3Kp110β. Moreover, in TN, a positive statistical correlation was observed between Beclin-1 or PI3Kp110β and MUC1-VNTR or NEU1, but not with EGFR. In conclusion, our data suggest that autophagy is reduced in TN leading likely to the deregulation of EGFR-MUC1-NEU1 complex and its associated cellular pathways.

Robust meta-analysis of gene expression using the elastic net

Meta-analysis of gene expression has enabled numerous insights into biological systems, but current methods have several limitations. We developed a method to perform a meta-analysis using the elastic net, a powerful and versatile approach for classification and regression. To demonstrate the utility of our method, we conducted a meta-analysis of lung cancer gene expression based on publicly available data. Using 629 samples from five data sets, we trained a multinomial classifier to distinguish between four lung cancer subtypes. Our meta-analysis-derived classifier included 58 genes and achieved 91% accuracy on leave-one-study-out cross-validation and on three independent data sets. Our method makes meta-analysis of gene expression more systematic and expands the range of questions that a meta-analysis can be used to address. As the amount of publicly available gene expression data continues to grow, our method will be an effective tool to help distill these data into knowledge.

MUC1 as a potential target in anticancer therapies

MUC1 is a glycoprotein that is overexpressed in tumor cells. In normal cells it forms a protective layer against microbes and toxic chemicals, besides providing lubrication on ductal surfaces. Oversecretion of MUC1 provide cancer cells with invasiveness, metastasis, and resistance to death induced by reactive oxygen species. MUC1 is made up of 2 heterodimers, MUC1-N and MUC1-C. MUC1-N is heavily glycosylated at 5 regions of the variable N-tandem repeats. MUC1-C is divisible into extracellular, intracellular, and cytoplasmic domain (MUC1-C/CD). The extracellular domain serves as a docking site for epidermal growth factor receptors and other receptor kinases; the transmembrane domain serves to relay messages from extracellular to MUC1-C/CD. The MUC1-C/CD has 5 phosphorylating sites that on interacting with the SH2 domain of specific proteins can stimulate tumor growth. Therapies targeting MUC1 consists of monoclonal antibodies (MAb), vaccines, or small molecules (aptamers). MAb therapies are mainly aimed at MUC1-N with little success, however, new generation of MAb are being developed for MUC1-C. Vaccines (peptide, carbohydrate, glycopeptide, DNA, and dendritic cell) have been developed that recognizes the aberrant glycosylated region of the variable N-tandem repeats in MUC1-N, whereas new generation vaccines are aimed at the cytoplasmic region of MUC1-C. Aptamers (peptides that resemble DNA, RNA) have been used for blocking the dimerization of CQC region and the 5 phosphorylating region of MUC1-C. In addition, aptamers have been used as cytotoxic drug carriers. However, none of the therapies for MUC1 are currently in clinical application, as they need further refinement and evaluation.

MUC1-mediated motility in breast cancer: a review highlighting the role of the MUC1/ICAM-1/Src signaling triad

Breast cancer is the most common cancer in women with the leading cause of death being metastasis, the spread of cancer to distant organs. For those patients with high-risk estrogen receptor positive (ER+) breast cancer, an increased expression of the glycoprotein MUC1 is associated with resistance to anti-hormonal therapy, metastasis and death. Tumor cells may use MUC1 to metastasize by exploiting the vascular adhesion pathways used by leukocytes during the inflammatory response. MUC1 is a type 1 transmembrane protein whose cytoplasmic tail acts as a scaffold for several signaling pathways including the non-receptor kinase Src, a signaling molecule involved in cell differentiation, proliferation, adhesion and motility. This review will highlight our current knowledge of how MUC1/ICAM-1 binding can lead to the recruitment and activation of Src and propose a novel role for lipid raft microdomains in this promigratory signaling. Improved understanding of the mechanism of metastases and the underlying signaling cascade is a prerequisite to the discovery of therapeutic targets to prevent metastasis and death in ER+ breast cancer patients.

Intracellular Targeting of the Oncogenic MUC1-C Protein with a Novel GO-203 Nanoparticle Formulation

PURPOSE

The MUC1-C oncoprotein is an intracellular target that is druggable with cell-penetrating peptide inhibitors. However, development of peptidyl drugs for treating cancer has been a challenge because of unfavorable pharmacokinetic parameters and limited cell-penetrating capabilities.

EXPERIMENTAL DESIGN

Encapsulation of the MUC1-C inhibitor GO-203 in novel polymeric nanoparticles was studied for effects on intracellular targeting of MUC1-C signaling and function.

RESULTS

Our results show that loading GO-203 into tetrablock polylactic acid (PLA)-polyethylene glycol (PEG)-polypropylene glycol (PPG)-PEG copolymers is achievable and, notably, is enhanced by increasing PEG chain length. In addition, we found that release of GO-203 from these nanoparticles is controllable over at least 7 days. GO-203/nanoparticle treatment of MUC1-C-positive breast and lung cancer cells in vitro was more active with less frequent dosing than that achieved with nonencapsulated GO-203. Moreover, treatment with GO-203/nanoparticles blocked MUC1-C homodimerization, consistent with on-target effects. GO-203/nanoparticle treatment was also effective in downregulating TIGAR, disrupting redox balance, and inhibiting the self-renewal capacity of cancer cells. Significantly, weekly administration of GO-203/nanoparticles to mice bearing syngeneic or xenograft tumors was associated with regressions that were comparable with those found when dosing on a daily basis with GO-203.

CONCLUSIONS

These findings thus define an effective approach for (i) sustained administration of GO-203 in polymeric PLA-(PEG-PPG-PEG) nanoparticles to target MUC1-C in cancer cells and (ii) the potential delivery of other anticancer peptide drugs.

Targeting the MUC1-C oncoprotein inhibits self-renewal capacity of breast cancer cells

The capacity of breast cancer cells to form mammospheres in non-adherent serum-free culture is used as a functional characteristic of the self-renewing stem-like cell population. The present studies demonstrate that silencing expression of the MUC1-C oncoprotein inhibits growth of luminal MCF-7 and HER2-overexpressing SKBR3 breast cancer cells as mammospheres. We also show that triple-negative MDA-MB-468 breast cancer cells are dependent on MUC1-C for growth as mammospheres and tumor xenografts. Similar results were obtained when MUC1-C function was inhibited by expression of a MUC1-C(CQC→AQA) mutant. Moreover, treatment with the MUC1-C inhibitor GO-203, a cell penetrating peptide that binds to the MUC1-C cytoplasmic domain and blocks MUC1-C function, confirmed the importance of this target for self-renewal. The mechanistic basis for these findings is supported by the demonstration that MUC1-C activates NF-κB, occupies the IL-8 promoter with NF-κB, and induces IL-8 transcription. MUC1-C also induces NF-κB-dependent expression of the IL-8 receptor, CXCR1. In concert with these results, targeting MUC1-C with GO-203 suppresses IL-8/CXCR1 expression and disrupts the formation of established mammospheres. Our findings indicate that MUC1-C contributes to the self-renewal of breast cancer cells by activating the NF-κB→IL-8/CXCR1 pathway and that targeting MUC1-C represents a potential approach for the treatment of this population.

MUC1-C activates the TAK1 inflammatory pathway in colon cancer

The mucin 1 (MUC1) oncoprotein has been linked to the inflammatory response by promoting cytokine-mediated activation of the NF-κB pathway. The TGF-β-activated kinase 1 (TAK1) is an essential effector of proinflammatory NF-κB signaling that also regulates cancer cell survival. The present studies demonstrate that the MUC1-C transmembrane subunit induces TAK1 expression in colon cancer cells. MUC1 also induces TAK1 in a MUC1(+/-)/IL-10(-/-) mouse model of colitis and colon tumorigenesis. We show that MUC1-C promotes NF-κB-mediated activation of TAK1 transcription and, in a positive regulatory loop, MUC1-C contributes to TAK1-induced NF-κB signaling. In this way, MUC1-C binds directly to TAK1 and confers the association of TAK1 with TRAF6, which is necessary for TAK1-mediated activation of NF-κB. Targeting MUC1-C thus suppresses the TAK1NF-κB pathway, downregulates BCL-XL and in turn sensitizes colon cancer cells to MEK inhibition. Analysis of colon cancer databases further indicates that MUC1, TAK1 and TRAF6 are upregulated in tumors associated with decreased survival and that MUC1-C-induced gene expression patterns predict poor outcomes in patients. These results support a model in which MUC1-C-induced TAK1NF-κB signaling contributes to intestinal inflammation and colon cancer progression.

Role of the unfolded protein response in regulating the mucin-dependent filamentous-growth mitogen-activated protein kinase pathway

Signaling mucins are evolutionarily conserved regulators of signal transduction pathways. The signaling mucin Msb2p regulates the Cdc42p-dependent mitogen-activated protein kinase (MAPK) pathway that controls filamentous growth in yeast. The cleavage and release of the glycosylated inhibitory domain of Msb2p is required for MAPK activation. We show here that proteolytic processing of Msb2p was induced by underglycosylation of its extracellular domain. Cleavage of underglycosylated Msb2p required the unfolded protein response (UPR), a quality control (QC) pathway that operates in the endoplasmic reticulum (ER). The UPR regulator Ire1p, which detects misfolded/underglycosylated proteins in the ER, controlled Msb2p cleavage by regulating transcriptional induction of Yps1p, the major protease that processes Msb2p. Accordingly, the UPR was required for differentiation to the filamentous cell type. Cleavage of Msb2p occurred in conditional trafficking mutants that trap secretory cargo in the endomembrane system. Processed Msb2p was delivered to the plasma membrane, and its turnover by the ubiquitin ligase Rsp5p and ESCRT attenuated the filamentous-growth pathway. We speculate that the QC pathways broadly regulate signaling glycoproteins and their cognate pathways by recognizing altered glycosylation patterns that can occur in response to extrinsic cues.

MUC1-C nuclear localization drives invasiveness of renal cancer cells through a sheddase/gamma secretase dependent pathway

MUC1 is a membrane-anchored mucin and its cytoplasmic tail (CT) can interact with many signaling pathways and act as a co-transcription factor to activate genes involved in tumor progression and metastasis. MUC1 is overexpressed in renal cell carcinoma with correlation to prognosis and has been implicated in the hypoxic pathway, the main renal carcinogenetic pathway. In this context, we assessed the effects of MUC1 overexpression on renal cancer cells properties. Using shRNA strategy and/or different MUC1 constructs, we found that MUC1-extracellular domain and MUC1-CT are involved in increase of migration, cell viability, resistance to anoikis and in decrease of cell aggregation in cancer cells. Invasiveness depends only on MUC1-CT. Then, by using siRNA strategy and/or pharmacological inhibitors or peptides, we showed that sheddases ADAM10, ADAM17 and gamma-secretase are necessary for MUC1 C-terminal subunit (MUC1-C) nuclear location and in increase of invasion property. Finally, MUC1 overexpression increases ADAM10/17 protein expression suggesting a positive regulatory loop. In conclusion, we report that MUC1 acts in renal cancer progression and MUC1-C nuclear localization drives invasiveness of cancer cells through a sheddase/gamma secretase dependent pathway. MUC1 appears as a therapeutic target by blocking MUC1 cleavage or nuclear translocation by using pharmacological approach and peptide strategies.

Transmembrane Mucin Expression and Function in Embryo Implantation and Placentation

Transmembrane mucins (TMs) are extremely large, complex glycoproteins that line the apical surfaces of simple epithelia including those of the female reproductive tract. TMs provide a physical barrier consistent with their role as part of the innate immune system. This barrier function must be overcome in the context of embryo implantation to permit blastocyst attachment. Three major TMs have been identified in uterine epithelia of multiple species: MUC1, MUC4, and MUC16. MUC1 has been found in all species studied to date, whereas expression of MUC4 and MUC16 have been less well studied and may be species specific. The strategies for removing mucins to permit embryo attachment also vary in a species-specific way and include both hormonal suppression of TM gene expression and membrane clearance via cell surface proteases. Studies emerging from the cancer literature indicate that TMs can modulate a surprisingly wide variety of signal transduction processes. Furthermore, various cell surface proteins have been identified that bind either the oligosaccharide or protein motifs of TMs suggesting that these molecules may support cell attachment in some contexts, including trophoblast interactions with cells of the immune system. The intimate association of TMs at sites of embryo-maternal interaction and the varied functions these complex molecules can play make them key players in embryo implantation and placentation processes.

The role of the small GTPase Rab31 in cancer

Members of the small GTPase family Rab are emerging as potentially important factors in cancer development and progression. A good number of Rabs have been implicated or associated with various human cancers, and much recent excitement has been associated with the roles of the Rab11 subfamily member Rab25 and its effector, the Rab coupling protein (RCP), in tumourigenesis and metastasis. In this review, we focus on a Rab5 subfamily member, Rab31, and its implicated role in cancer. Well recognized as a breast cancer marker with good prognostic value, recent findings have provided some insights as to the mechanism underlying Rab31's influence on oncogenesis. Levels of Oestrogen Receptor α (ERα)- responsive Rab31 could be elevated through stabilization of its transcript by the RNA binding protein HuR, or though activation by the oncoprotein mucin1-C (MUC1-C), which forms a transcriptional complex with ERα. Elevated Rab31 stabilizes MUC1-C levels in an auto-inductive loop that could lead to aberrant signalling and gene expression associated with cancer progression. Rab31 and its guanine nucleotide exchange factor GAPex-5 have, however, also been shown to enhance early endosome-late endosome transport and degradation of the epidermal growth factor receptor (EGFR). The multifaceted action and influences of Rab31 in cancer is discussed in the light of its new interacting partners and pathways.

The HER2 Signaling Network in Breast Cancer--Like a Spider in its Web

The human epidermal growth factor receptor 2 (HER2) is a major player in the survival and proliferation of tumour cells and is overexpressed in up to 30 % of breast cancer cases. A considerable amount of work has been undertaken to unravel the activity and function of HER2 to try and develop effective therapies that impede its action in HER2 positive breast tumours. Research has focused on exploring the HER2 activated phosphoinositide-3-kinase (PI3K)/AKT and rat sarcoma/mitogen-activated protein kinase (RAS/MAPK) pathways for therapies. Despite the advances, cases of drug resistance and recurrence of disease still remain a challenge to overcome. An important aspect for drug resistance is the complexity of the HER2 signaling network. This includes the crosstalk between HER2 and hormone receptors; its function as a transcription factor; the regulation of HER2 by protein-tyrosine phosphatases and a complex network of positive and negative feedback-loops. This review summarises the current knowledge of many different HER2 interactions to illustrate the complexity of the HER2 network from the transcription of HER2 to the effect of its downstream targets. Exploring the novel avenues of the HER2 signaling could yield a better understanding of treatment resistance and give rise to developing new and more effective therapies.

Role of the interaction between galectin-3 and cell adhesion molecules in cancer metastasis

Galectin-3, a unique chimera-type member of the β-galactoside-binding soluble lectin family, is present in both normal and cancer cells and plays a crucial role in the regulation of cell adhesion. It is involved both in accelerating detachment of cells from primary tumor sites and promoting cancer cell adhesion and survival to anoikis in the blood stream. Cell adhesion molecules (CAMs) are membrane receptors that mediate cell-cell and cell-matrix interactions, and are essential for transducing intracellular signals responsible for adhesion, migration, invasion, angiogenesis, and organ-specific metastasis. This review will discuss the recent advances in our understanding the biological functions, mechanism and therapeutic implication of the interaction between galectin-3 and CAMs in cancer metastasis.

MUC1-C Induces the LIN28B→LET-7→HMGA2 Axis to Regulate Self-Renewal in NSCLC

The LIN28B→let-7 pathway contributes to regulation of the epithelial-mesenchymal transition (EMT) and stem cell self-renewal. The oncogenic MUC1-C transmembrane protein is aberrantly overexpressed in lung and other carcinomas; however, there is no known association between MUC1-C and the LIN28B→let-7 pathway. Here in non-small cell lung cancer (NSCLC), silencing MUC1-C downregulates the RNA-binding protein LIN28B and coordinately increases the miRNA let-7. Targeting MUC1-C function with a dominant-negative mutant or a peptide inhibitor provided confirming evidence that MUC1-C induces LIN28B→let-7 signaling. Mechanistically, MUC1-C promotes NF-κB p65 chromatin occupancy of the LIN28B first intron and activates LIN28B transcription, which is associated with suppression of let-7. Consistent with let-7-mediated inhibition of HMGA2 transcripts, targeting of MUC1-C also decreases HMGA2 expression. HMGA2 has been linked to stemness, and functions as a competing endogenous RNA (ceRNA) of let-7-mediated regulation of the TGFβ coreceptor TGFBR3. Accordingly, targeting MUC1-C suppresses HMGA2 mRNA and protein, which is associated with decreases in TGFBR3, reversal of the EMT phenotype, and inhibition of self-renewal capacity. These findings support a model in which MUC1-C activates the ⇑LIN28B→⇓let-7→⇑HMGA2 axis in NSCLC and thereby promotes EMT traits and stemness.

IMPLICATIONS

A novel pathway is defined in which MUC1-C drives LIN28B→let-7→HMGA2 signaling, EMT, and self-renewal in NSCLC.

Genetics of gastric cancer

Gastric cancer remains highly prevalent and accounts for a notable proportion of global cancer mortality. This cancer is also associated with poor survival rates. Understanding the genetic basis of gastric cancer will offer insights into its pathogenesis, help identify new biomarkers and novel treatment targets, aid prognostication and could be central to developing individualized treatment strategies in the future. An inherited component contributes to <3% of gastric cancers; the majority of genetic changes associated with gastric cancer are acquired. Over the past few decades, advances in technology and high-throughput analysis have improved understanding of the molecular aspects of the pathogenesis of gastric cancer. These aspects are multifaceted and heterogeneous and represent a wide spectrum of several key genetic influences, such as chromosomal instability, microsatellite instability, changes in microRNA profile, somatic gene mutations or functional single nucleotide polymorphisms. These genetic aspects of the pathogenesis of gastric cancer will be addressed in this Review.

Targeting the oncogenic MUC1-C protein inhibits mutant EGFR-mediated signaling and survival in non-small cell lung cancer cells

PURPOSE

Non-small cell lung cancers (NSCLC) that express EGF receptor with activating mutations frequently develop resistance to EGFR kinase inhibitors. The mucin 1 (MUC1) heterodimeric protein is aberrantly overexpressed in NSCLC cells and confers a poor prognosis; however, the functional involvement of MUC1 in mutant EGFR signaling is not known.

EXPERIMENTAL DESIGN

Targeting the oncogenic MUC1 C-terminal subunit (MUC1-C) in NSCLC cells harboring mutant EGFR was studied for effects on signaling, growth, clonogenic survival, and tumorigenicity.

RESULTS

Stable silencing of MUC1-C in H1975/EGFR(L858R/T790M) cells resulted in downregulation of AKT signaling and inhibition of growth, colony formation, and tumorigenicity. Similar findings were obtained when MUC1-C was silenced in gefitinib-resistant PC9GR cells expressing EGFR(delE746_A750/T790M). The results further show that expression of a MUC1-C(CQC → AQA) mutant, which blocks MUC1-C homodimerization, suppresses EGFR(T790M), AKT and MEK → ERK activation, colony formation, and tumorigenicity. In concert with these results, treatment of H1975 and PC9GR cells with GO-203, a cell-penetrating peptide that blocks MUC1-C homodimerization, resulted in inhibition of EGFR, AKT, and MEK → ERK signaling and in loss of survival. Combination studies of GO-203 and afatinib, an irreversible inhibitor of EGFR, further demonstrate that these agents are synergistic in inhibiting growth of NSCLC cells harboring the activating EGFR(T790M) or EGFR(delE746-A750) mutants.

CONCLUSIONS

These findings indicate that targeting MUC1-C inhibits mutant EGFR signaling and survival, and thus represents a potential approach alone and in combination for the treatment of NSCLCs resistant to EGFR kinase inhibitors.

Protein mislocalization: mechanisms, functions and clinical applications in cancer

The changes from normal cells to cancer cells are primarily regulated by genome instability, which foster hallmark functions of cancer through multiple mechanisms including protein mislocalization. Mislocalization of these proteins, including oncoproteins, tumor suppressors, and other cancer-related proteins, can interfere with normal cellular function and cooperatively drive tumor development and metastasis. This review describes the cancer-related effects of protein subcellular mislocalization, the related mislocalization mechanisms, and the potential application of this knowledge to cancer diagnosis, prognosis, and therapy.

A signaling pathway consisting of miR-551b, catalase and MUC1 contributes to acquired apoptosis resistance and chemoresistance

Acquired chemoresistance is a major challenge in cancer therapy. While the oncoprotein Mucin-1 (MUC1) performs multiple roles in the development of diverse human tumors, whether MUC1 is involved in acquired chemoresistance has not been determined. Using an acquired chemoresistance lung cancer cell model, we show that MUC1 expression was substantially increased in cells with acquired apoptosis resistance (AR). Knockdown of MUC1 expression effectively increased the sensitivity of these cells to the apoptotic cytotoxicity of anticancer therapeutics, suggesting that MUC1 contributes to acquired chemoresistance. Decreased catalase expression and increased cellular reactive oxygen species (ROS) accumulation were found to be associated with MUC1 overexpression. Scavenging ROS with butylated hydroxyanisole or supplying exogenous catalase dramatically suppressed MUC1 expression through destabilizing MUC1 protein, suggesting that reduced catalase expression mediated ROS accumulation is accounted for MUC1 overexpression. Further, we found that increased miR-551b expression in the AR cells inhibited the expression of catalase and potentiated ROS accumulation and MUC1 expression. Finally, by manipulating MUC1 expression, we found that MUC1 promotes EGFR-mediated activation of the cell survival cascade involving Akt/c-FLIP/COX-2 in order to protect cancer cells from responding to anticancer agents. Thus, our results establish a pathway consisting of miR-551b/catalase/ROS that results in MUC1 overexpression, and intervention against this pathway could be exploited to overcome acquired chemoresistance.

STAT3 Target Genes Relevant to Human Cancers

Since its discovery, the STAT3 transcription factor has been extensively studied for its function as a transcriptional regulator and its role as a mediator of development, normal physiology, and pathology of many diseases, including cancers. These efforts have uncovered an array of genes that can be positively and negatively regulated by STAT3, alone and in cooperation with other transcription factors. Through regulating gene expression, STAT3 has been demonstrated to play a pivotal role in many cellular processes including oncogenesis, tumor growth and progression, and stemness. Interestingly, recent studies suggest that STAT3 may behave as a tumor suppressor by activating expression of genes known to inhibit tumorigenesis. Additional evidence suggested that STAT3 may elicit opposing effects depending on cellular context and tumor types. These mixed results signify the need for a deeper understanding of STAT3, including its upstream regulators, parallel transcription co-regulators, and downstream target genes. To help facilitate fulfilling this unmet need, this review will be primarily focused on STAT3 downstream target genes that have been validated to associate with tumorigenesis and/or malignant biology of human cancers.

Genetic regulation of MUC1 expression by Helicobacter pylori in gastric cancer cells

Helicobacter pylori infection of the stomach is associated with the development of gastritis, peptic ulcers, and gastric adenocarcinomas, but the mechanisms are unknown. MUC1 is aberrantly overexpressed by more than 50% of stomach cancers, but its role in carcinogenesis remains to be defined. The current studies were undertaken to identify the genetic mechanisms regulating H. pylori-dependent MUC1 expression by gastric epithelial cells. Treatment of AGS cells with H. pylori increased MUC1 mRNA and protein levels, and augmented MUC1 gene promoter activity, compared with untreated cells. H. pylori increased binding of STAT3 and MUC1 itself to the MUC1 gene promoter within a region containing a STAT3 binding site, and decreased CpG methylation of the MUC1 promoter proximal to the STAT3 binding site, compared with untreated cells. These results suggest that H. pylori upregulates MUC1 expression in gastric cancer cells through STAT3 and CpG hypomethylation.

MUC1 in macrophage: contributions to cigarette smoke-induced lung cancer

Expression of the pro-oncogenic mucin MUC1 is elevated by inflammation in airway epithelial cells, but the contributions of MUC1 to the development of lung cancer are uncertain. In this study, we developed our finding that cigarette smoke increases Muc1 expression in mouse lung macrophages, where we hypothesized MUC1 may contribute to cigarette smoke-induced transformation of bronchial epithelial cells. In human macrophages, cigarette smoke extract (CSE) strongly induced MUC1 expression through a mechanism involving the nuclear receptor PPAR-γ. CSE-induced extracellular signal-regulated kinase (ERK) activation was also required for MUC1 expression, but it had little effect on MUC1 transcription. RNA interference-mediated attenuation of MUC1 suppressed CSE-induced secretion of TNF-α from macrophages, by suppressing the activity of the TNF-α-converting enzyme (TACE), arguing that MUC1 is required for CSE-induced and TACE-mediated TNF-α secretion. Similarly, MUC1 blockade after CSE induction through suppression of PPAR-γ or ERK inhibited TACE activity and TNF-α secretion. Conditioned media from CSE-treated macrophages induced MUC1 expression and potentiated CSE-induced transformation of human bronchial epithelial cells in a TNF-α-dependent manner. Together, our results identify a signaling pathway involving PPAR-γ, ERK, and MUC1 for TNF-α secretion induced by CSE from macrophages. Furthermore, our results show how MUC1 contributes to smoking-induced lung cancers that are driven by inflammatory signals from macrophages.

MUC1 drives epithelial-mesenchymal transition in renal carcinoma through Wnt/β-catenin pathway and interaction with SNAIL promoter

MUC1 is overexpressed in human carcinomas. The transcription factor SNAIL can activate epithelial-mesenchymal transition (EMT) in cancer cells. In this study, in renal carcinoma, we demonstrate that (i) MUC1 and SNAIL were overexpressed in human sarcomatoid carcinomas, (ii) SNAIL increased indirectly MUC1 expression, (iii) MUC1 overexpression induced EMT, (iv) MUC1 C-terminal domain (MUC1-C) and β-catenin increased SNAIL transcriptional activity by interaction with its promoter and (v) blocking MUC1-C nuclear localization decreased Wnt/β-catenin signaling pathway activation and SNAIL expression. Altogether, our findings demonstrate that MUC1 is an actor in EMT and appears as a new therapeutic target.

Overview of cancer stem cells (CSCs) and mechanisms of their regulation: implications for cancer therapy

The identification of small subpopulations of cancer stem cells (CSCs) from blood mononuclear cells in human acute myeloid leukemia (AML) in 1997 was a landmark observation that recognized the potential role of CSCs in tumor aggressiveness. Two critical properties contribute to the functional role of CSCs in the establishment and recurrence of cancerous tumors: their capacity for self-renewal and their potential to differentiate into unlimited heterogeneous populations of cancer cells. These findings suggest that CSCs may represent novel therapeutic targets for the treatment and/or prevention of tumor progression, since they appear to be involved in cell migration, invasion, metastasis, and treatment resistance-all of which lead to poor clinical outcomes. The identification of CSC-specific markers, the isolation and characterization of CSCs from malignant tissues, and targeting strategies for the destruction of CSCs provide a novel opportunity for cancer research. This overview describes the potential implications of several common CSC markers in the identification of CSC subpopulations that are restricted to common malignant diseases, e.g., leukemia, and breast, prostate, pancreatic, and lung cancers. The role of microRNAs (miRNAs) in the regulation of CSC function is also discussed, as are several methods commonly used in CSC research. The potential role of the antidiabetic drug metformin- which has been shown to have effects on CSCs, and is known to function as an antitumor agent-is discussed as an example of this new class of chemotherapeutics.

MUC1-C oncoprotein promotes FLT3 receptor activation in acute myeloid leukemia cells

Blasts from approximately one-third of patients with acute myeloid leukemia (AML) harbor activating mutations in the FMS-like tyrosine kinase 3 (FLT3) receptor tyrosine kinase that confer a poor prognosis. The Mucin 1-C-terminal subunit (MUC1-C) oncoprotein is aberrantly expressed in AML blasts and stem cells; however, there is no known interaction between MUC1-C and FLT3. The present studies demonstrate that MUC1-C associates with wild-type and mutant FLT3 in AML cells. Targeting MUC1-C with the cell-penetrating peptide inhibitor GO-203 disrupts MUC1-C/FLT3 complexes and downregulates FLT3 activation. GO-203 treatment of AML cells was also associated with inhibition of the FLT3 downstream effectors AKT, extracellular signal-regulated kinase, and STAT5. The results further show that AML cells with FLT3-activating mutations and resistant to the FLT3 inhibitor midostaurin/PKC412 are sensitive to GO-203-induced growth arrest and death. Moreover, GO-203 increases sensitivity of mutant FLT3 AML cells to FLT3 inhibitor treatment. These results indicate that MUC1-C contributes to FLT3 activation in AML cells and that targeting MUC1-C inhibits the FLT3 signaling pathway. Our findings support the development of MUC1-C inhibitors alone and in combination with agents that target FLT3 for the treatment of wild-type and mutant FLT3 AML.

Using a cell line breast cancer progression system to identify biomarker candidates

Secreted and plasma membrane glycoproteins are considered excellent candidates for disease biomarkers. Herein we describe the identification of secreted and plasma membrane glycoproteins that are differentially expressed among a family of three breast cancer cell lines that models the progression of breast cancer. Using two-dimensional liquid chromatography-tandem mass spectrometry we identified more than 40 glycoproteins that were differentially expressed in either the premalignant (MCF10AT) or the fully malignant (MCF10CA1a) cell lines of this model system. Comparative analysis revealed that the differentially expressed breast cancer progression-associated glycoproteins were among the most highly expressed in the malignant (MCF10CA1a) breast cancer cell line; a subset of these was detected only in the malignant line; and others were detected in the malignant line at levels 25 to 50 times greater than in the benign (MCF10A) line. Using the results from this model cell system as a guide, we then carried out glycoproteomic analyses of normal and cancerous breast tissue lysates. Eleven of the glycoproteins differentially expressed in the breast cell lines were identified in the tissue lysates. Among these glycoproteins, collagen alpha-1 (XII) chain was expressed at dramatically higher (~10-fold) levels in breast cancer than in normal tissue.

BIOLOGICAL SIGNIFICANCE

Identifying glycoproteins differentially expressed during cancer progression results in information on the biological processes and key pathways associated with cancer. In addition, new hypotheses and potential biomarkers result from these glycoproteomic studies. Our glycoproteomic analysis of this model of breast cancer provides a roadmap for future experimental interventions to further tease apart critical components of tumor progression.

Usefulness of traditional serum biomarkers for management of breast cancer patients

The measurement of serum tumor markers levels in breast cancer (BC) patients is an economic and noninvasive diagnostic assay frequently requested by clinical oncologists to get information about the presence or absence of disease as well as its evolution. Despite their wide use in clinical practice, there is still an intense debate between scientific organizations about the real usefulness for patient monitoring during followup as well as response to therapy evaluation in case of advanced BC. In this review, we want to highlight the current recommendations published by scientific organizations about the use of “established” BC serum markers (CEA, TPA, TPS, CIFRA-21, CA15-3, and s-HER2) in clinical oncology practice. Moreover, we will focus on recent papers evidencing the usefulness of tumor markers levels measurement as a guide for the prescription and diagnostic integration of molecular imaging exams such as those performed by hybrid 18-fluorofeoxyglucose-positron emission tomography with integrated computed tomography. This technology is nowadays able to detect early cancer lesions undetectable by conventional morphological imaging investigation and most likely responsible for increasing of serum tumor markers levels.

Tanshinone IIA inhibits lipopolysaccharide-induced MUC1 overexpression in alveolar epithelial cells

The anti-inflammatory function of tanshinone IIA (TIIA), an active natural compound from Chinese herbal medicine Danshen, has been well recognized, and therefore TIIA has been widely used to treat various inflammatory conditions associated with cardiac and lung diseases. Mucin 1 (Muc1) plays important anti-inflammatory roles in resolution of acute lung inflammation. In this study, we investigated the effects of TIIA on LPS-induced acute lung inflammation, as well as its relationship to Muc1 expression in mouse lung and MUC1 in human alveolar epithelial cells. TIIA pretreatment significantly inhibited LPS-induced pulmonary inflammation in both Muc1 wild-type (Muc1(+/+)) and knockout (Muc1(-/-)) mice, as manifested by reduced neutrophil infiltration and reduced TNF-α and keratinocyte chemoattractant levels in bronchoalveolar lavage fluid. The inhibitory effects of TIIA on airway inflammation were associated with reduced expression of Muc1 in Muc1(+/+) mouse lung. Moreover, pretreatment with TIIA significantly inhibited LPS-induced MUC1 expression and TNF-α release in A549 alveolar epithelial cells. TNF-α upregulated MUC1 mRNA and protein expression in A549 cells, which was inhibited by pretreatment with TIIA. The LPS-induced MUC1 expression was blocked when A549 cells were transfected with siRNA targeting for TNF-α receptor 1. Furthermore, TIIA inhibited LPS-induced nuclear translocation of NF-κB and upregulation of Toll-like receptor 4 in A549 cells. Taken together, these results demonstrate that TIIA suppressed LPS-induced acute lung inflammation regardless of the presence of Muc1, and TIIA inhibited LPS- and TNF-α-induced MUC1/Muc1 expression in airway epithelial cells, suggesting that MUC1/Muc1 does not account for the mechanisms of the anti-inflammatory effects of TIIA in the airway.

MUC1 has prognostic significance in malignant peritoneal mesothelioma

BACKGROUND

Overexpression of MUC1 predicts poor survival in most cancers. Routine immunohistochemical detection of MUC1 is performed for differential diagnosis in malignant peritoneal mesothelioma (MPM). However, the prognostic significance of MUC1 in MPM has not been determined. 


METHOD

We investigated MUC1 expression and other prognostic factors in relation to survival in 42 patients (20 males and 22 females) for whom archival samples were available, using immunohistochemistry. MUC1 was expressed in 38/42 (90%) patients. Its prognostic significance was statistically analyzed using the Kaplan-Meier method.


RESULTS

High expression of MUC1 (immunohistochemical score of 5-8), was correlated with poor survival in several categories: all subtypes of tumors (p=0.001), male gender (p=0.017), female gender (p=0.001), epitheloid tumors (p=0.001), epitheloid tumors in males (p=0.005), epitheloid tumors in females (p=0.003), and age at diagnosis (AAD) <60 years (p=0.001). Amongst the other clinicopathological variables, univariate analysis also showed that male gender (p=0.007), sarcomatoid histology (p=0.001), peritoneal cancer index (PCI) ≥20 (p=0.013) and AAD ≥60 (p=0.001), correlated with poor survival. Multivariate analysis showed that only AAD ≥60 (p=0.049) was an independent prognostic factor, and that high MUC1 expression significantly correlated with the following categories: all subtypes of tumors (p=0.001), male gender (p=0.002), female gender (p=0.031), epitheloid tumors (p=0.031), and AAD <60y (p=0.012).


CONCLUSION

AAD and high MUC1 expression in the tumor are indicators of poor prognosis. MUC1 evaluation by immunohistochemistry may serve as a useful prognostic tool in MPM, but may need further confirmation in a larger patients' cohort.

MUC1 activates JNK1 and inhibits apoptosis under genotoxic stress

The MUC1 transmembrane glycoprotein is aberrantly overexpressed in diverse human carcinomas and has been shown to inhibit apoptosis induced by genotoxic agents. In the present work, we report that MUC1 binds to and activates JNK1, an important member of the mitogen-activated protein kinases (MAPK) superfamily. The physical interaction between MUC1 cytoplasmic domain (MUC1-CD) and JNK1 was established by GST-pull-down assay in vitro and co-immunoprecipitation assay in vivo. We show that MUC1 activates JNK1 and inhibits cisplatin-induced apoptosis in human colon cancer HCT116 cells. Pharmacological inhibition of JNK or knockdown of JNK significantly reduces the ability of MUC1 to inhibit cisplatin-induced apoptosis. Together, our data indicate that MUC1 can inhibit apoptosis via activating JNK1 pathway in response to genotoxic anticancer agents.