Comprehensive molecular profiling of UV-induced metastatic melanoma in Nme1/Nme2-deficient mice reveals novel markers of survival in human patients.

Hepatocyte growth factor-overexpressing mice that harbor a deletion of the Ink4a/p16 locus (HP mice) form melanomas with low metastatic potential in response to UV irradiation. Here we report that these tumors become highly metastatic following hemizygous deletion of the Nme1 and Nme2 metastasis suppressor genes (HPN mice). Whole-genome sequencing of melanomas from HPN mice revealed a striking increase in lung metastatic activity that is associated with missense mutations in eight signature genes (Arhgap35, Atp8b4, Brca1, Ift172, Kif21b, Nckap5, Pcdha2, and Zfp869). RNA-seq analysis of transcriptomes from HP and HPN primary melanomas identified a 32-gene signature (HPN lung metastasis signature) for which decreased expression is strongly associated with lung metastatic potential. Analysis of transcriptome data from The Cancer Genome Atlas revealed expression profiles of these genes that predict improved survival of patients with cutaneous or uveal melanoma. Silencing of three representative HPN lung metastasis signature genes (ARRDC3, NYNRIN, RND3) in human melanoma cells resulted in increased invasive activity, consistent with roles for these genes as mediators of the metastasis suppressor function of NME1 and NME2. In conclusion, our studies have identified a family of genes that mediate suppression of melanoma lung metastasis, and which may serve as prognostic markers and/or therapeutic targets for clinical management of metastatic melanoma.

Nme1 and Nme2 genes exert metastasis-suppressor activities in a genetically engineered mouse model of UV-induced melanoma.

NME1 is a metastasis-suppressor gene (MSG), capable of suppressing metastatic activity in cell lines of melanoma, breast carcinoma and other cancer origins without affecting their growth in culture or as primary tumours. Herein, we selectively ablated the tandemly arranged Nme1 and Nme2 genes to assess their individual impacts on metastatic activity in a mouse model (HGF:p16-/-) of ultraviolet radiation (UVR)-induced melanoma. Metastatic activity was strongly enhanced in both genders of Nme1- and Nme2-null mice, with stronger activity in females across all genotypes. The study ascribes MSG activity to Nme2 for the first time in an in vivo model of spontaneous cancer, as well as a novel metastasis-suppressor function to Nme1 in the specific context of UVR-induced melanoma.

A rare subpopulation of melanoma cells with low expression of metastasis suppressor NME1 is highly metastatic in vivo.

Despite recent advances in melanoma treatment, metastasis and resistance to therapy remain serious clinical challenges. NME1 is a metastasis suppressor, a class of proteins which inhibits metastatic spread of cancer cells without impact on growth of the primary tumor. We have identified a rare subpopulation of cells with markedly reduced expression of NME1 (NME1LOW) in human melanoma cell lines. To enable isolation of viable NME1LOW cells for phenotypic analysis by fluorescence-activated cell sorting (FACS), a CRISPR-Cas9-mediated approach was used to attach an EGFP coding module to the C-terminus of the endogenous NME1 gene in melanoma cell lines. NME1LOW cells displayed enhanced collective invasion in vitro when implanted as 3D aggregates in Matrigel. NME1LOW cells were also highly metastatic to lung and liver when xenografted subcutaneously in immune-deficient NSG mice. RNA-seq analysis revealed that NME1LOW cells express elevated levels of genes associated with tumor aggressiveness, as well as with morphogenesis of tissues of neural crest-like origin (melanocytes and neurons, bone and heart tissues; GO: 0009653). The highly malignant NME1LOW variant of melanoma cells has potential to provide novel therapeutic targets and molecular markers for improved clinical management of patients with advanced melanoma.

NME1 Drives Expansion of Melanoma Cells with Enhanced Tumor Growth and Metastatic Properties.

Melanoma is a lethal skin cancer prone to progression and metastasis, and resistant to therapy. Metastasis and therapy resistance of melanoma and other cancers are driven by tumor cell plasticity, largely via acquisition/loss of stem-like characteristics and transitions between epithelial and mesenchymal phenotypes (EMT/MET). NME1 is a metastasis suppressor gene that inhibits metastatic potential when its expression is enforced in melanoma and other cancers. Herein, we have unmasked a novel role for NME1 as a driver of melanoma growth distinct from its canonical function as a metastasis suppressor. NME1 promotes expansion of stem-like melanoma cells that exhibit elevated expression of stem cell markers (e.g., Sox2, Sox10, Oct-4, KLF4, and Ccnb-1), enhanced growth as melanoma spheres in culture, and enhanced tumor growth and lung colonizing activities in vivo. In contrast, NME1 expression did not affect the proliferation of melanoma cell lines in monolayer culture conditions. Silencing of NME1 expression resulted in a dramatic reduction in melanoma sphere size, and impaired tumor growth and metastatic activities of melanoma sphere cells when xenografted in immunocompromised mice. Individual cells within melanoma sphere cultures displayed a wide range of NME1 expression across multiple melanoma cell lines. Cell subpopulations with elevated NME1 expression were fast cycling and displayed enhanced expression of stem cell markers. IMPLICATIONS: Our findings suggest the current model of NME1 as a metastasis-suppressing factor requires refinement, bringing into consideration its heterogeneous expression within melanoma sphere cultures and its novel role in promoting the expansion and tumorigenicity of stem-like cells.

The metastasis suppressor NME1 inhibits melanoma cell motility via direct transcriptional induction of the integrin beta-3 gene.

Expression of the metastasis suppressor NME1 in melanoma is associated with reduced cellular motility, invasion, and metastasis, but mechanisms underlying these activities are not completely understood. Herein we report a novel mechanism through which NME1 drives formation of large, stable focal adhesions (FAs) in melanoma cells via induction of integrin ß3 (ITGß3), and in one cell line, concomitant suppression of integrin ß1 (ITGß1) transcripts. Forced expression of NME1 resulted in a strong activation of the promoter region (-301 to +13) of the ITGB3 gene. Chromatin immunoprecipitation (ChIP) analysis revealed the transcriptional induction was associated with direct recruitment of NME1 and an increase in the epigenetic activation mark, acetylation of histone 3 on lysine 27 (H3K27Ac) to a 1 kb stretch of 5'-flanking sequence of the ITGB3 gene. Unexpectedly, NME1 did not affect the amount either ITGß1 or ITGß3 proteins were internalized and recycled, processes commonly associated with regulating expression of integrins at the cell surface. The ability of NME1 to suppress motile and invasive phenotypes of melanoma cells was dependent on its induction of ITGß3. Expression of ITGß3 mRNA was associated with increased disease-free survival time in melanoma patients of the TCGA collection, consistent with its potential role as an effector of the metastasis suppressor function of NME1. Together, these data indicate metastasis suppressor activity of NME1 in melanoma is mediated by induction of ITGB3 gene transcription, with NME1-driven enrichment of ITGß3 protein at the cell membrane resulting in attenuated cell motility through the stabilization of large focal adhesions.

Metastasis Suppressor NME1 Directly Activates Transcription of the ALDOC Gene in Melanoma Cells.

BACKGROUND/AIM: NME/NM23 nucleoside diphosphate kinase 1 (NME1) is a metastasis suppressor gene, exhibiting reduced expression in metastatic cancers and the ability to suppress metastatic activity of cancer cells. We previously identified NME1-regulated genes with prognostic value in human melanoma. This study was conducted in melanoma cell lines aiming to elucidate the mechanism through which NME regulates one of these genes, aldolase C (ALDOC). MATERIALS AND METHODS: ALDOC mRNA and protein expression was measured using qRT-PCR and immunoblot analyses. Promoter-luciferase constructs and chromatin immunoprecipitation were employed to measure the impact of NME1 on ALDOC transcription. RESULTS: NME1 enhanced ALDOC transcription, evidenced by increased expression of ALDOC pre-mRNA and activity of an ALDOC promoter-luciferase module. NME1 was detected at the ALDOC promoter, and forced NME1 expression resulted in enhanced occupancy of the promoter by NME1, increased presence of epigenetic activation markers (H3K4me3 and H3K27ac), and recruitment of RNA polymerase II. CONCLUSION: This is the first study to indicate that NME1 induces transcription through its direct binding to the promoter region of a target gene.

Nuclear functions of NME proteins.

The NME family of proteins is composed of 10 isoforms, designated NME1-10, which are diverse in their enzymatic activities and patterns of subcellular localization. Each contains a conserved domain associated with a nucleoside diphosphate kinase (NDPK) function, although not all are catalytically active. Several of the NME isoforms (NME1, NME5, NME7, and NME8) also exhibit a 3'-5' exonuclease activity, suggesting roles in DNA proofreading and repair. NME1 and NME2 have been shown to translocate to the nucleus, although they lack a canonical nuclear localization signal. Binding of NME1 and NME2 to DNA does not appear to be sequence-specific in a strict sense, but instead is directed to single-stranded regions and/or other non-B-form structures. NME1 and NME2 have been identified as potential canonical transcription factors that regulate gene transcription through their DNA-binding activities. Indeed, the NME1 and NME2 isoforms have been shown to regulate gene expression programs in a number of cellular settings, and this regulatory function has been proposed to underlie their well-recognized ability to suppress the metastatic phenotype of cancer cells. Moreover, NME1 and, more recently, NME3, have been implicated in repair of both single- and double-stranded breaks in DNA. This suggests that reduced expression of NME proteins could contribute to the genomic instability that drives cancer progression. Clearly, a better understanding of the nuclear functions of NME1 and possibly other NME isoforms could provide critical insights into mechanisms underlying malignant progression in cancer. Indeed, clinical data indicate that the subcellular localization of NME1 may be an important prognostic marker in some cancers. This review summarizes putative functions of nuclear NME proteins in DNA binding, transcription, and DNA damage repair, and highlights their possible roles in cancer progression.

Identification of a gene expression signature associated with the metastasis suppressor function of NME1: prognostic value in human melanoma.

Although NME1 is well known for its ability to suppress metastasis of melanoma, the molecular mechanisms underlying this activity are not completely understood. Herein, we utilized a bioinformatics approach to systematically identify genes whose expression is correlated with the metastasis suppressor function of NME1. This was accomplished through a search for genes that were regulated by NME1, but not by NME1 variants lacking metastasis suppressor activity. This approach identified a number of novel genes, such as ALDOC, CXCL11, LRP1b, and XAGE1 as well as known targets such as NETO2, which were collectively designated as an NME1-Regulated Metastasis Suppressor Signature (MSS). The MSS was associated with prolonged overall survival in a large cohort of melanoma patients in The Cancer Genome Atlas (TCGA). The median overall survival of melanoma patients with elevated expression of the MSS genes was >5.6 years longer compared with that of patients with lower expression of the MSS genes. These data demonstrate that NMEl represents a powerful tool for identifying genes whose expression is associated with metastasis and survival of melanoma patients, suggesting their potential applications as prognostic markers and therapeutic targets in advanced forms of this lethal cancer.

The HGF/SF Mouse Model of UV-Induced Melanoma as an In Vivo Sensor for Metastasis-Regulating Gene.

Cutaneous malignant melanoma is an aggressive and potentially lethal form of skin cancer, particularly in its advanced and therapy-resistant stages, and the need for novel therapeutics and prognostic tools is acute. Incidence of melanoma has steadily increased over the past few decades, with exposure to the genome-damaging effects of ultraviolet radiation (UVR) well-recognized as a primary cause. A number of genetically-engineered mouse models (GEMMs) have been created that exhibit high incidence of spontaneous and induced forms of melanoma, and a select subset recapitulates its progression to aggressive and metastatic forms. These GEMMs hold considerable promise for providing insights into advanced stages of melanoma, such as potential therapeutic targets and prognostic markers, and as in vivo systems for testing of novel therapies. In this review, we summarize how the HGF/SF transgenic mouse has been used to reveal metastasis-regulating activity of four different genes (CDK4R24C, survivin and NME1/NME2) in the context of UV-induced melanoma. We also discuss how these models can potentially yield new strategies for clinical management of melanoma in its most aggressive forms.

Harvesting multipotent progenitor cells from a small sample of tonsillar biopsy for clinical applications.

BACKGROUND: Human adult stem cells hold the potential for the cure of numerous conditions and degenerative diseases. They possess major advantages over pluripotent stem cells as they can be derived from donors at any age, and therefore pose no ethical concerns or risk of teratoma tumor formation in vivo. Furthermore, they have a natural ability to differentiate and secrete factors that promote tissue healing without genetic manipulation. However, at present, clinical applications of adult stem cells are limited by a shortage of a reliable, standardized, and easily accessible tissue source which does not rely on specimens discarded from unrelated surgical procedures. METHOD: Human tonsil-derived mesenchymal progenitor cells (MPCs) were isolated from a small sample of tonsillar tissue (average 0.88 cm3). Our novel procedure poses a minimal mechanical and enzymatic insult to the tissue, and therefore leads to high cell viability and yield. We characterized these MPCs and demonstrated robust multipotency in vitro. We further show that these cells can be propagated and maintained in xeno-free conditions. RESULTS: We have generated tonsillar biopsy-derived MPC (T-MPC) lines from multiple donors across a spectrum of age, sex, and race, and successfully expanded them in culture. We characterized them by cell surface markers, as well as in vitro expansion and differentiation potential. Our procedure provides a robust yield of tonsillar biopsy-derived T-MPCs. CONCLUSIONS: Millions of MPCs can be harvested from a sample smaller than 1 g, which can be collected from a fully awake donor in an outpatient setting without the need for general anesthesia or hospitalization. Our study identifies tonsillar biopsy as an abundant source of adult MPCs for regenerative medicine.

The Ezh2 polycomb group protein drives an aggressive phenotype in melanoma cancer stem cells and is a target of diet derived sulforaphane.

Melanoma is a metastatic cancer associated with poor survival. Here, we study a subpopulation of melanoma cancer cells displaying melanoma cancer stem cell (MCS cells) properties including elevated expression of stem cell markers, increased ability to survive as spheroids, and enhanced cell migration and invasion. We show that the Ezh2 stem cell survival protein is enriched in MCS cells and that Ezh2 knockdown or treatment with small molecule Ezh2 inhibitors, GSK126 or EPZ-6438, reduces Ezh2 activity. This reduction is associated with a reduced MCS cell spheroid formation, migration, and invasion. Moreover, the diet-derived cancer prevention agent, sulforaphane (SFN), suppresses MCS cell survival and this is associated with loss of Ezh2. Forced expression of Ezh2 partially reverses SFN suppression of MCS cell spheroid formation, migration, and invasion. A375 melanoma cell-derived MCS cells form rapidly growing tumors in immune-compromised mice and SFN treatment of these tumors reduces tumor growth and this is associated with reduced Ezh2 level and H3K27me3 formation, reduced matrix metalloproteinase expression, increased TIMP3 expression and increased apoptosis. These studies identify Ezh2 as a MCS cell marker and cancer stem cell prevention target, and suggest that SFN acts to reduce melanoma tumor formation via a mechanism that includes suppression of Ezh2 function. © 2015 Wiley Periodicals, Inc.

Metastasis suppressor NME1 regulates melanoma cell morphology, self-adhesion and motility via induction of fibronectin expression.

Expression of the metastasis suppressor NME1 in melanoma is associated with reduced cellular motility and invasion in vitro and metastasis in vivo, but the underlying molecular mechanisms are not completely understood. Herein, we report a novel mechanism through which NME1 controls melanoma cell morphology via upregulation of the extracellular matrix (ECM) protein fibronectin. Expression of NME1 strongly suppressed cell motility in melanoma cell lines 1205LU and M14. The resulting sedentary phenotype was associated with a more flattened appearance and marked increases in actin stress fibre and focal adhesion formation. NME1-induced focal adhesions were colocalized with dense deposits of fibronectin, which were absent or minimal in the corresponding NME1-deficient parental lines. NME1 was a strong inducer of fibronectin mRNA and protein expression, shown with reciprocal approaches of forced NME1 expression and shRNA-mediated knock-down. Increased synthesis and ECM deposition of fibronectin was necessary for NME1-induced cell spreading, as knock-down of fibronectin opposed the effects of NME1 on cell morphology. Fibronectin knock-down also reversed the ability of NME1 to promote aggregation when cells were plated on a non-adherent substratum. Similarly, inhibiting activation of the fibronectin receptor integrin α4ß1 with an anti-α4 antibody reversed the motility-suppressing effect of NME1. A positive correlation was observed between NME1 and fibronectin mRNA in clinical biopsies of normal skin, benign nevi and primary melanomas, but not in metastatic forms, suggesting the NME1/fibronectin axis represents a barrier to melanoma progression. In summary, these findings indicate fibronectin is an important effector of the motility-suppressing function of NME1 in melanoma cells.

Dual functions of NME1 in suppression of cell motility and enhancement of genomic stability in melanoma.

The NME1 gene represents the prototypical metastasis suppressor, whose expression inhibits cell motility and metastasis without impact on primary tumor growth in a number of different human cancers. This report outlines our recent efforts to define the molecular mechanisms through which NME1 both suppresses cell motility and promotes genomic integrity in the setting of human melanoma. Forced NME1 expression in a variety of melanoma-derived cell lines was shown to induce dynamic changes in cell morphology and reorganization of the actin cytoskeleton, with formation of a network of thick stress fibers and assembly of fibronectin fibrils at large focal adhesions. Moreover, NME1 expression results in adhesion reprogramming through an impact on integrin repertoire and focal adhesion dynamics. Having previously demonstrated that NME1 expression promotes repair of DNA damage induced by ultraviolet radiation (UVR) in both yeast and mammalian cells, probably via the nucleotide excision repair pathway, we have more recently demonstrated that NME1 is rapidly recruited to double-strand breaks. This preliminary result represents the first evidence of direct interactions between NME1 and DNA in the context of DNA repair and has set the stage for current efforts to probe its functional interactions with double-strand break repair pathways. Discussed herein are molecular models to explain the interactions of NME1 with such diverse cellular functions as cell motility and DNA repair, potentially through its nucleoside diphosphate kinase and 3'-5' exonuclease activities.

CD151-α3ß1 integrin complexes suppress ovarian tumor growth by repressing slug-mediated EMT and canonical Wnt signaling.

Human ovarian cancer is diagnosed in the late, metastatic stages but the underlying mechanisms remain poorly understood. We report a surprising functional link between CD151-α3ß1 integrin complexes and the malignancy of serous-type ovarian cancer. Analyses of clinical specimens indicate that CD151 expression is significantly reduced or diminished in 90% of metastatic lesions, while it remains detectable in 58% of primary tumors. These observations suggest a putative tumor-suppressing role of CD151 in ovarian cancer. Indeed, our analyses show that knocking down CD151 or α3 integrin enhances tumor cell proliferation, growth and ascites production in nude mice. These changes are accompanied by impaired cell-cell contacts and aberrant expression of E-cadherin, Mucin 5AC and fibronectin, largely reminiscent of an epithelial to mesenchymal transition (EMT)-like change. Importantly, Slug, a master regulator of EMT, is markedly elevated. Knocking down Slug partially restores CD151-α3ß1 integrin complex-dependent suppression of cell proliferation. Moreover, disruption of these adhesion protein complexes is accompanied by a concomitant activation of canonical Wnt signaling, including elevated levels of ß-catenin and Axin-2 as well as resistance to the inhibition in ß-catenin-dependent transcriptional complexes. Together, our study demonstrates that CD151-α3ß1 integrin complexes regulate ovarian tumor growth by repressing Slug-mediated EMT and Wnt signaling.

The metastasis suppressor NME1 regulates expression of genes linked to metastasis and patient outcome in melanoma and breast carcinoma.

NME1 is a well-documented metastasis suppressor gene, with suppressor activity demonstrated across a wide spectrum of human cancers including melanoma and carcinomas of the breast, stomach and thyroid. A primary aim of the current study was to identify profiles of genes whose expression is regulated by NME1 in cell lines of melanoma and thyroid carcinoma origin. Impact of NME1 was determined by forcing its expression transiently in cell lines using a novel Ad5-based adenoviral vector (Ad5-NME1), followed 48 h later by analysis of RNA expression profiles using the U133A microarray chip. Robust NME1 expression was achieved following infection with the Ad5-NME1 adenovirus in the human metastasis-derived cell lines WM1158 (melanoma) and WRO82 (follicular thyroid carcinoma), resulting in wide-ranging effects on gene expression in both settings. A substantial proportion of the NME1-regulated genes identified in the analyses were of clear potential relevance to metastasis, such as matrix metalloproteinase-1 (MMP1), angiopoietin-2 (ANGPT2), SERPINB9 and colony stimulating factor receptor-2B (CSFR2B). Nine genes were identified (false discovery rate <0.1) that were regulated by NME1 in both the WM1158 and WRO82 cell lines, each possessing one or more such metastasis-relevant activities as stress fiber formation and focal adhesion (PPM1E, ZYX, PFN1), chemotaxis (CCR1) epithelial-mesenchymal signaling (WNT6), differentiation and morphogenesis (TBX4, ZFP36L2), and G protein modulation (GPR52 and PFN1). In addition, a number of the NME1-regulated genes were shown to be of prognostic value for distant disease-free survival and overall survival in melanoma and breast cancer. The combined expression of three NME1-regulated genes CSFR2B, MSF4A1 and SERPINB9 provided a strongly synergistic correlation with distant disease-free survival in the basal subtype of breast cancer (p<3.5e(-5), hazard ratio=0.33). Our study demonstrates that analysis of NME1-dependent gene expression is a powerful approach for identifying potential modulators of metastatic potential in multiple cancer types, which in turn may represent useful therapeutic targets. The study also highlights NME1-dependent genes as potential prognostic/diagnostic indices, which are profoundly lacking at present in melanoma.

c-Abl and Arg induce cathepsin-mediated lysosomal degradation of the NM23-H1 metastasis suppressor in invasive cancer.

Metastasis suppressors comprise a growing class of genes whose downregulation triggers metastatic progression. In contrast to tumor suppressors, metastasis suppressors are rarely mutated or deleted, and little is known regarding the mechanisms by which their expression is downregulated. Here, we demonstrate that the metastasis suppressor, NM23-H1, is degraded by lysosomal cysteine cathepsins (L,B), which directly cleave NM23-H1. In addition, activation of c-Abl and Arg oncoproteins induces NM23-H1 degradation in invasive cancer cells by increasing cysteine cathepsin transcription and activation. Moreover, c-Abl activates cathepsins by promoting endosome maturation, which facilitates trafficking of NM23-H1 to the lysosome where it is degraded. Importantly, the invasion- and metastasis-promoting activity of c-Abl/Arg is dependent on their ability to induce NM23-H1 degradation, and the pathway is clinically relevant as c-Abl/Arg activity and NM23-H1 expression are inversely correlated in primary breast cancers and melanomas. Thus, we demonstrate a novel mechanism by which cathepsin expression is upregulated in cancer cells (via Abl kinases). We also identify a novel role for intracellular cathepsins in invasion and metastasis (degradation of a metastasis suppressor). Finally, we identify novel crosstalk between oncogenic and metastasis suppressor pathways, thereby providing mechanistic insight into the process of NM23-H1 loss, which may pave the way for new strategies to restore NM23-H1 expression and block metastatic progression.

NM23 deficiency promotes metastasis in a UV radiation-induced mouse model of human melanoma.

Cutaneous malignant melanoma is the most lethal form of skin cancer, with 5-year survival rates of <5 % for patients presenting with metastatic disease. Mechanisms underlying metastatic spread of UVR-induced melanoma are not well understood, in part due to a paucity of animal models that accurately recapitulate the disease in its advanced forms. We have employed a transgenic mouse strain harboring a tandem deletion of the nm23-m1 and nm23-m2 genes to assess the combined contribution of these genes to suppression of melanoma metastasis. Crossing of the nm23-h1/nm23-h2 knockout in hemizygous-null form ([m1m2](+/-)) to a transgenic mouse strain (hepatocyte growth factor/scatter factor-overexpressing, or HGF(+) strain) vulnerable to poorly-metastatic, UVR-induced melanomas resulted in UVR-induced melanomas with high metastatic potential. Metastasis to draining lymph nodes was seen in almost all cases of back skin melanomas, while aggressive metastasis to lung, thoracic cavity, liver and bone also occurred. Interestingly, no differences were observed in the invasive characteristics of primary melanomas of HGF(+) and HGF(+) × [m1m2](+/-) strains, with both exhibiting invasion into the dermis and subcutis, indicating factors other than simple invasive activity were responsible for metastasis of HGF(+) × [m1m2](+/-) melanomas. Stable cell lines were established from the primary and metastatic melanoma lesions from these mice, with HGF(+) × [m1m2](+/-) lines exhibiting increased single cell migration and genomic instability. These studies demonstrate for the first time in vivo a potent metastasis suppressor activity of NM23 in UVR-induced melanoma, and have provided new tools for identifying molecular mechanisms that underlie melanoma metastasis.

Integrin-associated CD151 drives ErbB2-evoked mammary tumor onset and metastasis.

ErbB2+ human breast cancer is a major clinical problem. Prior results have suggested that tetraspanin CD151 might contribute to ErbB2-driven breast cancer growth, survival, and metastasis. In other cancer types, CD151 sometimes supports tumor growth and metastasis. However, a definitive test of CD151 effects on de novo breast cancer initiation, growth, and metastasis has not previously been done. We used CD151 gene-deleted mice expressing the MMTV-ErbB2 transgene to show that CD151 strongly supports ErbB2+ mammary tumor initiation and metastasis. Delayed tumor onset (by 70-100 days) in the absence of CD151 was accompanied by reduced survival of mammary epithelial cells and impaired activation of FAK- and MAPK-dependent pathways. Both primary tumors and metastatic nodules showed smooth, regular borders, consistent with a less invasive phenotype. Furthermore, consistent with impaired oncogenesis and decreased metastasis, CD151-targeted MCF-10A/ErbB2 cells showed substantial decreases in three-dimensional colony formation, EGF-stimulated tumor cell motility, invasion, and transendothelial migration. These CD151-dependent functions were largely mediated through α6ß4 integrin. Moreover, CD151 ablation substantially prevented PKC- and EGFR/ERK-dependent α6ß4 integrin phosphorylation, consistent with retention of epithelial cell polarity and intermediate filament cytoskeletal connections, which helps to explain diminished metastasis. Finally, clinical data analyses revealed a strong correlation between CD151 and ErbB2 expression and metastasis-free survival of breast cancer patients. In conclusion, we provide strong evidence that CD151 collaborates with LB integrins (particularly α6ß4 and ErbB2 (and EGFR) receptors to regulate multiple signaling pathways, thereby driving mammary tumor onset, survival, and metastasis. Consequently, CD151 is a useful therapeutic target in malignant ErbB2+ breast cancer.

Metastasis suppressor NM23-H1 promotes repair of UV-induced DNA damage and suppresses UV-induced melanomagenesis.

Reduced expression of the metastasis suppressor NM23-H1 is associated with aggressive forms of multiple cancers. Here, we establish that NM23-H1 (termed H1 isoform in human, M1 in mouse) and two of its attendant enzymatic activities, the 3'-5' exonuclease and nucleoside diphosphate kinase, are novel participants in the cellular response to UV radiation (UVR)-induced DNA damage. NM23-H1 deficiency compromised the kinetics of repair for total DNA polymerase-blocking lesions and nucleotide excision repair of (6-4) photoproducts in vitro. Kinase activity of NM23-H1 was critical for rapid repair of both polychromatic UVB/UVA-induced (290-400 nm) and UVC-induced (254 nm) DNA damage, whereas its 3'-5' exonuclease activity was dominant in the suppression of UVR-induced mutagenesis. Consistent with its role in DNA repair, NM23-H1 rapidly translocated to sites of UVR-induced (6-4) photoproduct DNA damage in the nucleus. In addition, transgenic mice hemizygous-null for nm23-m1 and nm23-m2 exhibited UVR-induced melanoma and follicular infundibular cyst formation, and tumor-associated melanocytes displayed invasion into adjacent dermis, consistent with loss of invasion-suppressing activity of NM23 in vivo. Taken together, our data show a critical role for NM23 isoforms in limiting mutagenesis and suppressing UVR-induced melanomagenesis.