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Cancer is one of the most dreaded diseases of the 21st century for humans. Currently, the human cancer mortality rate is approximately 11-25%. However, for some animals, such as elephants, the cancer mortality rate is lower than 5%. p53 is a significant cellular regulator in human cancers, and its important role in response to DNA damage has been highlighted by the discovery of p53 retrogene found in elephants (19 copies) but not humans (0 copies). Therefore, the main question is whether (1) more copies of p53 are better at combating cancer development or (2) is elephant p53 is better than human p53 in p53-mediated function? Herein, we demonstrate for the first time that N-terminal and C-terminal elephant-to-human p53 variants and truncations alter p53 transactivation. First, we created elephant-to-human p53 variants (such as T387R, L383P, LSTEL, etc.) and truncations at the N-terminus and C-terminus of human p53. Secondly, R175H and R273H p53 mutants (conformational and contact mutants, respectively) were used as negative control. Using a p53 (14X) response element LUC and several natural p53 downstream gene promoters, we demonstrated that several N-terminal and C-terminal p53 variants and truncations increases p53 transactivation compared to WT p53. Moreover, we found that deletion of the region between aa374 and aa382 is integral for p53 transactivation. Taken together, our preliminary results demonstrate that several N-terminal and C-terminal elephant-to-human p53 variants enhance p53 transactivation and possible stability. This data is the first step to support the notion that elephant p53 is better than human p53 in p53-mediated function. Citation Format: William H. Yang, Wei-Hsiung Yang. N-terminal and C-terminal elephant-to-human p53 variants and truncations alter p53 transactivation. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3735.

USAAP-1 protein mainly consists of proteins belonging to c-Jun, c-Fos, activating transcription factor (ATF), and Jun dimerization protein (JDP) family. In addition to AP-1 site, JDP2 also binds to cAMP responsive element (CRE) site in numerous cis-elements of the target genes. JDP2 has been shown to be involved in cancer development and cell-cycle regulation, suppression of adipocyte differentiation, and controlling bone homeostasis and antibacterial immunity. ATF3 and JDP2 share high similarity in C-terminal domains with identities of 65%. Previous studies have demonstrated that ATF3 can bind to p53 and regulate p53 transcriptional activity and stability. Though couple of studies have shown that JDP2 inhibits expression of p53 and p53 represses the transcriptional activity of JDP2 promoter; however, whether JDP2 directly interacts and regulates p53 transactivation remains largely unknown. Herein, we demonstrate for the first time that JDP2 can directly interact with p53. First, we found that both ATF3 and JDP2 can bind to p53 and the C-terminus of JDP2 is required for p53 binding. Secondly, in p53-null H1299 cells, JDP2 dose-dependently enhances p53 transactivation using p53RE-Luc (14X). Moreover, we demonstrated that JDP2 dose-dependently decreases p53 protein level in consistence with the previous reports. Finally, JDP2 increases p53 stability in CHX chase experiments. Taken together, our results demonstrate that JDP2 directly binds to p53 and enhances p53 transactivation and stability, suggesting that JDP2 is a novel regulator of p53. Citation Format: Wei-Hsiung Yang, Kasey Price, Leticia Cardoso, William Yang, Chiung-Min Wang, Richard Yang. JDP2 interacts with p53 and enhances p53 transactivation and stability [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5723.

Members of the microRNA (miR)-200 family, which are involved in tumor metastasis, have potential as cancer biomarkers, but their regulatory mechanisms remain elusive. We investigated FOXP3-inducible breast cancer cells, Foxp3 heterozygous Scurfy mutant (Foxp3 sf/+ ) female mice, and patients with breast cancer for characterization of the formation and regulation of the miR-200 family in breast cancer cells and circulation. Participants (259), including patients with breast cancer or benign breast tumors, members of breast cancer families, and healthy controls, were assessed for tumor and circulating levels of the miR-200 family. First, we identified a FOXP3-KAT2B-miR-200c/141 axis in breast cancer cells. Second, aging Foxp3 sf/+ female mice developed spontaneous breast cancers and lung metastases. Levels of miR-200c and miR-141 were lower in Foxp3 sf/+ tumor cells than in normal breast epithelial cells, but plasma levels of miR-200c and miR-141 in the Foxp3 sf/+ mice increased during tumor progression and metastasis. Third, in patients with breast cancer, the levels of miR-200c and 141 were lower in FOXP3 low relative to those with FOXP3 high breast cancer cells, especially in late-stage and metastatic cancer cells. The levels of miR-200c and miR-141 were higher in plasma from patients with metastatic breast cancer than in plasma from those with localized breast cancer, with benign breast tumors, with a family history of breast cancer, or from healthy controls. Finally, in Foxp3 sf/+ mice, plasma miR-200c and miR-141 appeared to be released from tumor cells. miR-200c and miR-141 are regulated by a FOXP3-KAT2B axis in breast cancer cells, and circulating levels of miR-200c and miR-141 are potential biomarkers for early detection of breast cancer metastases.

Fibrinogen is an extracellular matrix protein composed of three polypeptide chains with fibrinogen alpha (FGA), beta (FGB) and gamma (FGG). Although fibrinogen and its related fragments are involved in tumor angiogenesis and metastasis, their functional roles are incompatible. A recent genome-scale screening reveals that loss of FGA affects the acceleration of tumor growth and metastasis of lung cancer, but the mechanism remains elusive. We used CRISPR/Cas9 genome editing to knockout (KO) FGA in human lung adenocarcinoma (LUAD) cell lines A549 and H1299. By colony formation, transwell migration and matrix invasion assays, FGA KO increased cell proliferation, migration, and invasion but decreased the expressions of epithelial–mesenchymal transition marker E-cadherin and cytokeratin 5/8 in A549 and H1299 cells. However, administration of FGA inhibited cell proliferation and migration but induced apoptosis in A549 cells. Of note, FGA KO cells indirectly cocultured by transwells with FGA wild-type cells increased FGA in the culture medium, leading to decreased migration of FGA KO cells. Furthermore, our functional analysis identified a direct interaction of FGA with integrin α5 as well as FGA–integrin signaling that regulated the AKT–mTOR signaling pathway in A549 cells. In addition, we validated that FGA KO increased tumor growth and metastasis through activation of AKT signaling in an A549 xenograft model. Implications: These findings demonstrate that that loss of FGA facilities tumor growth and metastasis through the integrin–AKT signaling pathway in lung cancer.

Programmed Cell Death Protein 4 (PDCD4), a well-known tumor suppressor, acts to inhibit translation initiation and cap-dependent translation by inhibiting the helicase activity of EIF4A. EIF4A tends to target mRNAs with structured 5'-UTR. PDCD4 can also prevent tumorigenesis by inhibiting tumor promoter-induced neoplastic transformation, and studies indicate that PDCD4 may inhibit translation of certain mRNAs via directly binding. A previous study has demonstrated that PDCD4 inhibits translation of p53 mRNA and treatment with DNA-damaging agents down-regulates PDCD4 expression but activates p53 expression. The study further demonstrated that treatment with DNA-damaging agents resulted in down-regulation of PDCD4 expression and an increase in p53 expression, suggesting a potential mechanism in which p53 regulates expression of Pdcd4. However, whether p53 directly regulates PDCD4 remains unknown. Herein, we demonstrate for the first time that p53 regulates PDCD4 expression. First, we found that overexpression of p53 in p53-null cells (H1299 and Saos2 cells) decreased PDCD4 protein level. Secondly, p53 dose-dependently decreased PDCD4 promoter activity in gene reporter assays. Moreover, we demonstrated that mutations on p53 (R273H: contact mutant, hotspot and R175H: conformational mutant, hotspot) abolished p53-mediated PDCD4 repression. Furthermore, using Tet-on expression system, PDCD4 protein level was decreased when WT p53, but not hotspot mutants of p53, was expressed in H1299 cells. Finally, mutations on DNA-binding domain, but not C-terminal regulatory domain, of p53 disrupted p53-mediated PDCD4 repression. Taken together, our results suggest that p53 functions as a novel regulator of PDCD4 and the relationship between of p53 and PDCD4 may be involved in tumor development and progression. Citation Format: Wei-Hsiung Yang, Andrew P. George, William H. Yang, Chiung-Min Wang, Richard H. Yang. Tumor suppressor p53 down-regulates programmed cell death protein 4 (PDCD4) expression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2160.

Purpose: In prostate cancer cells, there is CD24-dependent inactivation of mutant p53, but the mechanism and its significance remain largely unknown. Here, we validated this observation and explored the therapeutic potential of targeting CD24 in TP53 mutant prostate cancer cells. Experimental Design: Overall, 553 prostate cancers (522 formalin-fixed paraffin-embedded and 31 frozen tissues) were assessed for protein or mRNA expression of CD24 and TP53. The effects of CD24 on p53-dependent transcriptional regulation, cancer cell growth, the cell cycle, apoptosis, and mutant p53 restoration were also determined. Results: As determined with three sample cohorts, CD24 and p53 were not expressed in prostate epithelial cells but in prostate cancer cells in 48% of cases for CD24 and 16% of cases for p53 (mutant form). Expressions of CD24 and mutant p53 were more frequently observed in late-stage and metastatic prostate tumors. Mutant p53 accompanied with CD24 was expressed in most cases (91.6%, 76/83). Silencing of CD24 increased the transcriptional activity of p53 target genes, such as CDKNA1, VDR, and TP53INP1, leading to suppression of p53-dependent cell growth, cell-cycle arrest, and apoptosis in most TP53-mutant prostate cancer cells. Silencing of CD24 enhanced restoration of PRIMA-1–induced mutant p53 in endogenous TP53P223L/V274F DU145 cells and in PC3 cells transfected with TP53R273H. Conclusions: In human prostate cancers, there is CD24-dependent inactivation of mutant p53. The coexpression of CD24 and p53 may help identify aggressive cancers. Targeting CD24 provides a strategy to enhance mutant p53-restoring therapies, especially in patients with TP53R273H prostate cancer. Clin Cancer Res; 22(10); 2545–54. ©2015 AACR.

Activating transcription factor 3 (ATF3), a stress sensor, is rapidly induced by a variety of physiological and pathological signals, including those from cancer cells, and is essential in the complex processes of stress response. Several lines of evidence have demonstrated that ATF3 is involved in host defense and cancer development. Several studies also provide the relationship between ATF3 and p53 indicating that ATF3 binds to and stabilizes p53 while ATF3 is a negative regulator of TP53 gene expression. FOXP3, a well-known breast and prostate tumor suppressor, is a novel transcriptional repressor for several oncogenes including SKP2. However, whether ATF3 is the target protein of FOXP3 remains unknown. Herein, we demonstrate that ATF3 expression is regulated by FOXP3. First, we observed that overexpression of FOXP3 reduced ATF3 protein level in several cancer cell lines (H1299, HepG2, and Ishikawa cells). Secondly, FOXP3 dose-dependently reduced ATF3 promoter activity in gene reporter assay in several cell lines (MCF7, H1299, MDAMB231, and Saos2 cells). Since FOXP3 is regulated by post-translational modifications (PTMs), we next investigated whether PTMs affect FOXP3-mediated ATF3 expression. Interestingly, we observed that phosphorylation mutation on FOXP3 (Y342F) abolished FOXP3-mediated ATF3 expression. However, other PTM mutations on FOXP3, including S418 phosphorylation, K263 acetylation and ubiquitination, and K268 acetylation and ubiquitination, did not alter FOXP3-mediated ATF3 expression. Finally, FOXP3 binding site was found on ATF3 promoter region, around -870 bp region. Taken together, our results suggest that FOXP3 functions as a novel regulator of ATF3 and this novel event may be involved in tumor development and progression. Citation Format: Wei-Hsiung Yang, Chiung-Min Wang, William Yang. Transcription factors FOXP3 regulate ATF3 expression [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 310A.

The tumor-suppressive activity of FOXP3 has been observed in tumor initiation, but the underlying mechanism still remains largely unknown. Here, we identified a FOXP3–microRNA-146 (miR-146)–NF-κB axis in vitro and in vivo in prostate cancer cells. We observed that FOXP3 dramatically induced the expression of miR-146a/b, which contributed to transcriptional inhibition of IRAK1 and TRAF6, in prostate cancer cell lines. Tissue-specific deletion of Foxp3 in mouse prostate caused a significant reduction of miR-146a and upregulation of NF-κB activation. In addition, prostatic intraepithelial neoplasia lesions were observed in miR-146a–mutant mice as well as in Foxp3-mutant mice. Notably, the NF-κB inhibitor bortezomib inhibited cell proliferation and induced apoptosis in prostate epithelial cells, attenuating prostatic intraepithelial neoplasia formation in Foxp3-mutant mice. Our data suggest that the FOXP3–miR-146–NF-κB axis has a functional role during tumor initiation in prostate cancer. Targeting the miR-146–NF-κB axis may provide a new therapeutic approach for prostate cancers with FOXP3 defects. Cancer Res; 75(8); 1714–24. ©2015 AACR.

Transcription factor Forkhead Box Protein M1 (FOXM1) is a well-known master regulator in controlling cell-cycle pathways essential for DNA replication and mitosis, as well as cell proliferation. Among the three major isoforms of FOXM1, FOXM1B is highly associated with tumor growth and metastasis. The activities of FOXM1B are modulated by post-translational modifications (PTMs), such as phosphorylation, but whether it is modified by small ubiquitin-related modifier (SUMO) remains unknown. The aim of the current study was to determine whether FOXM1B is post-translationally modified by SUMO proteins and also to identify SUMOylation of FOXM1B on its target gene transcription activity. Here we report that FOXM1B is clearly defined as a SUMO target protein at the cellular levels. Moreover, a SUMOylation protease, SENP2, significantly decreased SUMOylation of FOXM1B. Notably, FOXM1B is selectively SUMOylated at lysine residue 463. While SUMOylation of FOXM1B is required for full repression of its target genes MiR-200b/c and p21, SUMOylation of FOXM1B is essential for full activation of JNK1 gene. Overall, we provide evidence that FOXM1B is post-translationally modified by SUMO and SUMOylation of FOXM1B plays a functional role in regulation of its target gene activities.

S-phase kinase-associated protein 2 (SKP2), a component of the E3 ubiquitin ligase SKP1-CUL1-Fbox complex, acts as an oncogene/oncoprotein as evidence suggests that overexpression of SKP2 results in cell cycle dysregulation and tumorigenesis as well as associates with poor prognosis in numerous cancers. The unique peptidyl-propyl isomerase PIN1, which isomerizes the cis-trans peptide bond between pSer/pThr and proline, regulates its target proteins’ cell localization, stability, and function. However, whether SKP2 is the target protein of PIN1 remains unknown. Herein, we demonstrate that SKP2 expression is regulated by PIN1 and FOXP3. First, we observed that knock-down PIN1 using siRNAs reduced SKP2 protein level in several cancer cell lines (MCF7, PC3, DU145, HepG2, and JEG3 cells). Secondly, we found that overexpression of PIN1 increased SKP2 protein level. Furthermore, PIN1 dose-dependently enhanced SKP2 promoter activity in gene reporter assay. Since FOXP3 is a known transcriptional repressor for the oncogene SKP2, we investigated whether PIN1 affects FOXP3-mediated SKP2 expression. Interestingly, we observed that PIN1 dose-dependently counteracted FOXP3-mediated SKP2 promoter activity. Finally, we demonstrated that mutations on PIN1 (W34A) and FOXP3 (Y342F) abolished PIN1-mediated and FOXP3-mediated SKP2 expression, respectively. Taken together, our results suggest that PIN1 functions as a novel regulator of SKP2 and with FOXP3 may be involved in tumor development and progression. Citation Format: Wei-Hsiung Yang, Chiung-Min Wang, William H. Yang. PIN1 and FOXP3 regulate SKP2 expression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 181A.

In this review, we introduce the IPEX syndrome and its relationship with germline mutations of the FOXP3 gene. We then describe the multiple functional roles of FOXP3 in regulatory T cells and epithelial cells as well as in IPEX syndrome and tumor progression. Potential mechanisms of FOXP3 inactivation and transcriptional regulation are discussed with recent advances. Finally, we point out current issues and a potential FOXP3-mediated therapeutic strategy as well as the reactivation of FOXP3 in patients with IPEX syndrome and cancer.

Adrenocortical carcinomas are rare but present with extremely poor prognosis. One of the approaches to control cancer progression and reduce cancer risk is prevention through diet. Bitter melon is widely consumed as a vegetable and especially as a traditional medicine in many countries. In this study, we have used human and mouse adrenocortical cancer cells as an in vitro model to assess the efficacy of bitter melon extract (BME) as an anticancer agent. The protein concentrations of BME and other extracts were measured before use. First, BME treatment of adrenocortical cancer cells resulted in a significantly dose-dependent decrease in cell proliferation. However, we did not observe an antiproliferative effect in adrenocortical cancer cells treated with extracts from blueberry, zucchini, and acorn squash. Second, apoptosis of adrenocortical cancer cells was accompanied by increased caspase-3 activation and poly(ADP-ribose) polymerase cleavage. BME treatment enhanced cellular tumor antigen p53, cyclin-dependent kinase inhibitor 1A (also called p21), and cyclic AMP-dependent transcription factor-3 levels and inhibited G1/S-specific cyclin D1, D2, and D3, and mitogen-activated protein kinase 8 (also called Janus kinase) expression, suggesting an additional mechanism involving cell cycle regulation and cell survival. Third, BME treatment decreased the key proteins involved in steroidogenesis in adrenocortical cancer cells. BME treatment decreased the level of phosphorylation of cyclin-dependent kinase 7, which is required, at least in part, for steroidogenic factor 1 activation. Finally, we observed that BME treatment significantly reduced the level of insulin-like growth factor 1 receptor and its downstream signaling pathway as evidenced by lower levels of phosphorylated RAC-α serine/threonine-protein kinase. Taken together, these data illustrate the inhibitory effect of bitter melon on cell proliferation of adrenocortical cancer through modulation of diverse mechanisms.

Cyclic AMP-dependent transcription factor-3 (ATF3), a stress sensor/mediator, plays an essential role in cells to maintain homeostasis and has diverse functions in cellular death and survival signal pathways. ATF3 binds to the consensus ATF/cAMP response element (CRE) to regulate its downstream target genes, such as CCNE2 (Cyclin E2), CD82 (KAI1), DDIT3 (GADD153), LDLR (LDL receptor), SNAI1, TP53, and TWIST1. A previous report has shown that the activities of ATF3 are modulated by ubiquitination; however, whether it is modified by small ubiquitin-related modifier (SUMO), an important modification in regulating a wide range of cellular processes, remains unknown. The aim of this study was to investigate whether ATF3 is post-translationally modified by SUMO proteins and also to determine the role of SUMOylation of ATF3 on MC2R, NR5A1, STAR, and TP53 gene activities. Here we demonstrate that ATF3 is clearly defined as a SUMO target protein both in vitro SUMOylation assay using recombinant proteins and at the cellular levels. Furthermore, ATF3 interacted with UBE2I (Ubc9), the only SUMO E2 enzyme found so far. In addition, PIAS3β (a SUMO E3 ligase) enhanced and SENP2 and SENP7 (two SUMOylation proteases) decreased SUMOylation of ATF3, respectively. In addition, we found that ATF3 is selectively SUMOylated at lysine residue 42 but the SUMOylation/deSUMOylation does not alter subcellular localization of ATF3. We next characterized the functional role of ATF3 SUMOylation on MC2R, NR5A1, STAR, and TP53 gene expression. We found that SUMOylation of ATF3 is required for full repression of NR5A1 and TP53 genes. While SUMOylation of ATF3 is required for full activation of MC2R gene activity, SUMOylation of ATF3 further enhances repression of STAR gene activity. Overall, we provide the first evidence that ATF3 is post-translationally modified by SUMO to regulate MC2R, NR5A1, STAR, and TP53 gene activities. Citation Format: Chiung-Min Wang, Victoria Brennan, Ninoska Gutierrez, Xirui Wang, Lizhong Wang, Wei-Hsiung Yang. SUMOylation of ATF3 alters MC2R, NR5A1, STAR, and TP53 gene activities. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 763A. doi:10.1158/1538-7445.AM2013-763A

Malignant adrenal tumors or adrenocortical carcinomas are relatively rare; however, this form of cancer is highly malignant and presents with extremely poor prognosis as a consequence of metastasis or local invasion at the time of diagnosis. One of the approaches to control cancer progression and reduce cancer risk is prevention through diet. Bitter melon is widely consumed as a vegetable and especially as a traditional medicine in China, India, Japan, and Taiwan. In this study, we have used human and mouse adrenocortical cancer cells, H295R and Y1, respectively, as an in vitro model to assess the efficacy of bitter melon extract (BME) as an anticancer agent. First, we find that BME treatment of adrenocortical cancer cells results in a significant dose-dependent decrease in cell proliferation and growth. We also find that bitter melon extract has stronger anti-proliferation effect than blueberry extract on adrenocortical cancer cells. As expected, extracts from Acorn squash and Zucchini, two vegetables from the same Family of Cucurbitaceae as bitter melon, do not decrease cell proliferation in adrenocortical cancer cells. Second, apoptosis of adrenocortical cancer cells is accompanied by increased caspase activation and poly(ADP-ribose) polymerase cleavage. Further studies reveal that BME treatment enhances p53, p21, Mdm2, and ATF3 and inhibits cyclin D1, cyclin D2, cycline D3, mTOR, and JNK expression, suggesting an additional mechanism involving cell cycle regulation, cell motility, cell survival, and cell differentiation. Third, BME treatment also decreases steroidogenic activities in adrenocortical cancer cells by Western blotting and reporter gene assay. BME treatment of adrenocortical cancer cells results in a significant dose-dependent decrease in levels of NR5A1/SF1, MC2R, StAR proteins. Interestingly, we find that BME treatment decreases the level of phospho-CDK7, which is required, at least in part, for NR5A1/SF1 activation. Taken together, these data illustrate that inhibitory effect of bitter melon on the growth and proliferation of adrenocortical cancer cells through modulation of the cell cycle regulation and steroidogenic pathways. Therefore, BME can be used as a dietary supplement for prevention of adrenocortical cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5587. doi:10.1158/1538-7445.AM2011-5587