Id1 expression is transcriptionally regulated in radial growth phase melanomas

ALDH2 is a novel biomarker and exerts an inhibitory effect on melanoma

Melanoma is a malignant skin tumor. This study aimed to explore and assess the effect of novel biomarkers on the progression of melanoma. Differently expressed genes (DEGs) were screened from GSE3189 and GSE46517 datasets of Gene Expression Omnibus database using GEO2R. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses were conducted based on the identified DEGs. Hub genes were identified and assessed using protein-protein interaction networks, principal component analysis, and receiver operating characteristic curves. Quantitative real-time polymerase chain reaction was employed to measure the mRNA expression levels. TIMER revealed the association between aldehyde dehydrogenase 2 (ALDH2) and tumor immune microenvironment. The viability, proliferation, migration, and invasion were detected by cell counting kit-8, 5-ethynyl-2'-deoxyuridine, wound healing, and transwell assays. Total 241 common DEGs were screened out from GSE3189 and GSE46517 datasets. We determined 6 hub genes with high prediction values for melanoma, which could distinguish tumor samples from normal samples. ALDH2, ADH1B, ALDH3A2, DPT, EPHX2, and GATM were down-regulated in A375 and SK-MEL-2 cells, compared with the human normal melanin cell line (PIG1 cells). ALDH2 was selected as the candidate gene in this research, presenting a high diagnostic and predictive value for melanoma. ALDH2 had a positive correlation with the infiltrating levels of immune cells in melanoma microenvironment. Overexpression of ALDH2 inhibited cell viability, proliferation, migration, and invasion of A375/SK-MEL-2 cells. ALDH2 is a new gene biomarker of melanoma, which exerts an inhibitory effect on melanoma.

Id Proteins Contribute to Tumor Development and Metastatic Colonization in a Model of Bladder Carcinogenesis

Background: Bladder cancer is one of the most common malignant genitourinary diseases worldwide. Despite advances in surgical technique, medical oncology and radiation therapy, cure of invasive tumors remains elusive for patients with late stage disease. Therefore, new therapeutic strategies are needed to improve the response rates with regard to recurrence, invasion and metastasis.

Objective: Inhibitor of DNA binding (Id) proteins have been proposed as therapeutic targets due to the key regulatory role they exert in multiple steps of cancer. We aimed to explore the role of Id proteins in bladder cancer development and the pattern of expression of Id proteins in bladder carcinomas.

Methods: We used a well-established chemically induced model of bladder carcinogenesis. Wild type and Id-deficient mice were given N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN) in the drinking water and urinary bladder lesions were analyzed histopathologically and stained for Id1. We assessed the effects of Id1 inactivation in cultured bladder cancer cells and in a model of metastatic lung colonization. We also performed Id1 staining of human urothelial carcinoma samples and matched lymph node metastases.

Results: Id1 protein was overexpressed in the BBN-induced model of bladder cancer. Id1 deficiency resulted in the development of urinary bladder tumors with areas of extensive hemorrhage and decreased invasiveness when compared to wild type mice. Id1 inactivation led to decreased cell growth in vitro and lung colonization in vivo of human bladder cancer cells. Immunohistochemistry performed on human urothelial carcinoma samples showed Id1 positive staining in both primary tumors and lymph node metastases.

Conclusions: In summary, our studies reveal the physiological relevance of Id1 in bladder cancer progression and suggest that targeting Id1 may be important in the development of novel therapies for the treatment of bladder cancer.

Expression and function of the ID1 gene during transforming growth factor-β1-induced differentiation of human embryonic stem cells to endothelial cells

ID1 can mediate transforming growth factor-β (TGF-β)/activin receptor-like kinase-1 (ALK1)-induced (and Smad-dependent) migration in endothelial cells (ECs). However, the role that ID1 plays during differentiation of human embryonic stem cells (hESCs) into ECs induced by TGF-β1 remains unclear. In this study, a hESC differentiation model that recapitulates the developmental steps of vasculogenesis during the early stages of embryonic development was used to explore this question. We found that TGF-β1 increases endothelial cell differentiation and inhibits endothelial tube formation. Furthermore, at an early stage of differentiation, TGF-β1 may induce in vitro differentiation of hESCs into ECs by inhibiting expression of ID1, while at a later stage of differentiation, TGF-β1 may stimulate the proliferation and migration of ECs via the ALK1/Smad1/5/ID1 pathway. Downregulation of ID1 by gene silencing can lead to acceleration of TGF-β1-induced hESC differentiation into ECs and inhibition of proliferation and migration of ECs. This study may reveal some mechanisms of in vivo vasculogenesis in the early stages of embryonic development.

MK615, a Prunus mume Steb. Et Zucc ('Ume') extract, attenuates the growth of A375 melanoma cells by inhibiting the ERK1/2-Id-1 pathway

The Japanese apricot, a commonly consumed food called 'Ume' in Japan, has been used for a traditional Japanese medicine for centuries. MK615, an extract of compounds from 'Ume', has strong antitumorigenic and antiinflammatory effects including the induction of apoptosis and autophagy, and inhibition of cytokine production mediated via the inhibition of MAPKs signaling including ERK-1/2, JNK and p38MAPK. The inhibitor of DNA binding 1 (Id-1), a basic helix-loop-helix (bHLH) transcription factor family, is essential for DNA binding and the transcriptional regulation of various proteins that play important roles in the development, progression and invasion of tumors. In melanoma, Id-1 is constitutively expressed in the late and early stages, suggesting it as a therapeutic target in patients with melanoma. This study reports that MK615 profoundly reduced both the mRNA- and protein expression levels of Id-1 and inhibited cell growth in A375 melanoma cells. MK615 markedly inhibited the phosphorylation of ERK1/2, which is associated with Id-1 protein expression in A375 cells. Id-1-specific RNAi induced the death of A375 cells. Moreover, the expression of Bcl-2 was decreased by both MK615 and Id-1-specific RNAi in A375 cells. The results suggest that MK615 is a potential therapeutic agent for treating malignant melanoma.

Expression of Id-1 is regulated by MCAM/MUC18: a missing link in melanoma progression

The acquisition of the metastatic melanoma phenotype is associated with increased expression of the melanoma cell adhesion molecule MCAM/MUC18 (CD146). However, the mechanism by which MUC18 contributes to melanoma metastasis remains unclear. Herein, we stably silenced MUC18 expression in two metastatic melanoma cell lines, A375SM and C8161, and conducted cDNA microarray analysis. We identified and validated that the transcriptional regulator, inhibitor of DNA binding-1 (Id-1), previously shown to function as an oncogene in several malignancies, including melanoma, was downregulated by 5.6-fold following MUC18 silencing. Additionally, we found that MUC18 regulated Id-1 expression at the transcriptional level via ATF-3, which itself was upregulated by 6.9-fold in our cDNA microarray analysis. ChIP analysis showed increased binding of ATF-3 to the Id-1 promoter after MUC18 silencing. To complement these studies, we rescued the expression of MUC18, which reversed the expression patterns of Id-1 and ATF-3. Moreover, we showed that MUC18 promotes melanoma invasion through Id-1, as overexpression of Id-1 in MUC18-silenced cells resulted in increased MMP-2 expression and activity. To our knowledge, this is the first demonstration that MUC18 is involved in cell signaling regulating the expression of Id-1 and ATF-3, thus contributing to melanoma metastasis.

Id1 overexpression is independent of repression and epigenetic silencing of tumor suppressor genes in melanoma

The full molecular consequences of oncogene activation during tumorigenesis are not well understood, but several studies have recently linked oncogene activation to epigenetic silencing of specific genes 1, 2. Transcriptional repressor Id1 is overexpressed in many malignancies including melanoma, and Id1 targets include tumor suppressor genes TSP1, CDKN2A (p16) and CDKN1A (p21), which are frequently epigenetically silenced in cancer. We confirmed that both TSP1 and CDKN2A have abnormal promoter region DNA methylation in primary melanoma, but the mechanism by which this silencing occurs remains unknown. Here we explore the effects of stable lentiviral Id1 overexpression on the expression of these Id1 target genes in human melanoma cell lines. Overexpressed Id1 was functional and bound transcriptional activator E2A, but did not sequester E2A from gene promoters and repress gene expression. Therefore, these Id1 target genes were resistant to Id1-mediated gene silencing. Our results suggest that Id1 activation may need to occur at discrete stages in cooperation with additional gene dysregulation to repress and induce epigenetic silencing of tumor suppressor genes during melanoma progression.

Evidence of gamma-tocotrienol as an apoptosis-inducing, invasion-suppressing, and chemotherapy drug-sensitizing agent in human melanoma cells

To date, the most effective cure for metastatic melanoma remains the surgical resection of the primary tumor. Recently, tocotrienol-rich-fraction has shown antiproliferative effect on cancer cells. To elucidate this anticancer property in malignant melanoma, this study aimed, first, to identify the most potent isomer for eliminating melanoma cells and second to decipher the molecular pathway responsible for its activity. Results showed that the inhibitory effect of gamma-tocotrienol was most potent, which resulted in induction of apoptosis as evidenced by activation of procaspases and the accumulation of sub-G1 cell population. Examination of the prosurvival genes revealed that the gamma-tocotrienol-induced cell death was associated with suppression of NF-kappaB, EGF-R, and Id family proteins. Meanwhile, gamma-tocotrienol treatment also resulted in induction of JNK signaling pathway, and inhibition of JNK activity by selective inhibitor was able to partially block the effect of gamma-tocotrienol. Interestingly, gamma-tocotrienol treatment led to suppression of mesenchymal markers and the restoration of E-cadherin and gamma-catenin expression, which was associated with suppression of cell invasion capability. Furthermore, synergistic effect was observed when cells were cotreated with gamma-tocotrienol and chemotherapy drugs. Together, our results demonstrated for the first time the anti-invasion and chemonsensitization effect of gamma-tocotrienol against human malignant melanoma cells.

Apigenin inhibits proliferation of ovarian cancer A2780 cells through Id1

Apigenin, a common dietary flavonoid, has been shown to possess anti-tumor properties. However, the mechanism by which apigenin inhibits cancer cells is not fully understood. Id1 (inhibitor of differentiation or DNA binding protein 1) contributes to tumorigenesis by stimulating cell proliferation, inhibiting cell differentiation and facilitating tumor neoangiogenesis. Elevated Id1 is found in ovarian cancers and its level correlates with the malignant potential of ovarian tumors. Therefore, Id1 is a potential target for ovarian cancer treatment. Here, we demonstrate that apigenin inhibits proliferation and tumorigenesis of human ovarian cancer A2780 cells through Id1. Apigenin suppressed the expression of Id1 through activating transcription factor 3 (ATF3). Our results may elucidate a new mechanism underlying the inhibitory effects of apigenin on cancer cells.

Prostate cancer-associated gene expression alterations determined from needle biopsies

PURPOSE

To accurately identify gene expression alterations that differentiate neoplastic from normal prostate epithelium using an approach that avoids contamination by unwanted cellular components and is not compromised by acute gene expression changes associated with tumor devascularization and resulting ischemia.

EXPERIMENTAL DESIGN

Approximately 3,000 neoplastic and benign prostate epithelial cells were isolated using laser capture microdissection from snap-frozen prostate biopsy specimens provided by 31 patients who subsequently participated in a clinical trial of preoperative chemotherapy. cDNA synthesized from amplified total RNA was hybridized to custom-made microarrays composed of 6,200 clones derived from the Prostate Expression Database. Expression differences for selected genes were verified using quantitative reverse transcription-PCR.

RESULTS

Comparative analyses identified 954 transcript alterations associated with cancer (q < 0.01%), including 149 differentially expressed genes with no known functional roles. Gene expression changes associated with ischemia and surgical removal of the prostate gland were absent. Genes up-regulated in prostate cancer were statistically enriched in categories related to cellular metabolism, energy use, signal transduction, and molecular transport. Genes down-regulated in prostate cancers were enriched in categories related to immune response, cellular responses to pathogens, and apoptosis. A heterogeneous pattern of androgen receptor expression changes was noted. In exploratory analyses, androgen receptor down-regulation was associated with a lower probability of cancer relapse after neoadjuvant chemotherapy followed by radical prostatectomy.

CONCLUSIONS

Assessments of tumor phenotypes based on gene expression for treatment stratification and drug targeting of oncogenic alterations may best be ascertained using biopsy-based analyses where the effects of ischemia do not complicate interpretation.

Concerted potent humoral immune responses to autoantigens are associated with tumor destruction and favorable clinical outcomes without autoimmunity

PURPOSE

The therapeutic importance of immune responses against single versus multiple antigens is poorly understood. There also remains insufficient understanding whether responses to one subset of antigens are more significant than another. Autoantibodies are frequent in cancer patients. They can pose no biological significance or lead to debilitating paraneoplastic syndromes. Autoreactivity has been associated with clinical benefits, but the magnitude necessary for meaningful results is unknown. Autologous tumor cells engineered to secrete granulocyte macrophage colony-stimulating factor generate immune infiltrates in preexisting metastases with associated tumor destruction. We sought to identify targets of responses from this vaccination strategy.

EXPERIMENTAL DESIGN

Postvaccination sera used in screening a cDNA expression library prepared from a densely infiltrated metastasis of a long-term surviving melanoma patient identified several autoantigens. Additional autoantigens were identified through similar screenings in non-small cell lung cancer and murine models, and proteins implicated in cancer propagation. ELISAs for several targets were established using recombinant proteins, whereas others were evaluated by petit serologies.

RESULTS

Eleven gene products were identified through serologic screening from two patients showing highly favorable clinical outcomes. A subset of antigens revealed significant changes in antibody titers compared with weak responses to other proteins. Time course analyses showed coordinated enhanced titers against several targets as a function of vaccination in responding patients.

CONCLUSIONS

This study shows the range of biologically significant antigens resulting from a whole-cell vaccine. Targets include autoantigens that are components of cell cycle regulation. Potent antibody responses against multiple autoantigens are associated with effective tumor destruction without clinical autoimmunity.

Id1 delays senescence of primary human melanocytes

The Id family of helix-loop-helix transcription factors is upregulated in a variety of human malignancies and has been implicated in promoting tumorigenesis through effects on cell growth, differentiation, and tumor angiogenesis. While expression of Id proteins has been associated with tumorigenesis, the precise mechanistic relationship between Id expression and carcinogenesis has not been clearly delineated. We have previously shown that Id1 delays cellular senescence in primary mammalian cells through inhibition of the cell cycle regulatory protein and familial melanoma gene, p16/INK4a. We have also demonstrated that Id1 expression is upregulated in early stage primary human melanomas and may be an important marker for early malignancy. In order to further define the role of Id1 in human melanoma development, we have evaluated the function of Id1 in primary human melanocytes. Here we show that constitutive expression of Id1 in primary human melanocytes leads to delayed cellular senescence and decreased expression of the familial melanoma gene, p16/INK4a. Although melanocytes constitutively expressing Id1 are shown to possess extended lifespans, this is not associated with an appreciable change in cell growth or telomere length. We conclude that Id1 delays cellular senescence in primary human melanocytes through inhibition of p16/INK4a expression and suggest that Id1 may contribute to the malignant conversion of primary human melanocytes through extension of cellular lifespan.