Zhifeng Yu

Bio: Zhifeng Yu is an academic researcher from Baylor College of Medicine. The author has contributed to research in topics: Sperm & Cancer. The author has an hindex of 15, co-authored 33 publications receiving 1248 citations.

High-grade serous ovarian cancer arises from fallopian tube in a mouse model

Abstract: Although ovarian cancer is the most lethal gynecologic malignancy in women, little is known about how the cancer initiates and metastasizes. In the last decade, new evidence has challenged the dogma that the ovary is the main source of this cancer. The fallopian tube has been proposed instead as the primary origin of high-grade serous ovarian cancer, the subtype causing 70% of ovarian cancer deaths. By conditionally deleting Dicer, an essential gene for microRNA synthesis, and Pten, a key negative regulator of the PI3K pathway, we show that high-grade serous carcinomas arise from the fallopian tube in mice. In these Dicer-Pten double-knockout mice, primary fallopian tube tumors spread to engulf the ovary and then aggressively metastasize throughout the abdominal cavity, causing ascites and killing 100% of the mice by 13 mo. Besides the clinical resemblance to human serous cancers, these fallopian tube cancers highly express genes that are known to be up-regulated in human serous ovarian cancers, also demonstrating molecular similarities. Although ovariectomized mice continue to develop high-grade serous cancers, removal of the fallopian tube at an early age prevents cancer formation—confirming the fallopian tube origin of the cancer. Intriguingly, the primary carcinomas are first observed in the stroma of the fallopian tube, suggesting that these epithelial cancers have a mesenchymal origin. Thus, this mouse model demonstrates a paradigm for the origin and initiation of high-grade serous ovarian carcinomas, the most common and deadliest ovarian cancer.

Molecular Profiling Uncovers a p53-Associated Role for MicroRNA-31 in Inhibiting the Proliferation of Serous Ovarian Carcinomas and Other Cancers

Abstract: MicroRNAs (miRNA) regulate complex patterns of gene expression, and the relevance of altered miRNA expression to ovarian cancer remains to be elucidated. By comprehensively profiling expression of miRNAs and mRNAs in serous ovarian tumors and cell lines and normal ovarian surface epithelium, we identified hundreds of potential miRNA-mRNA targeting associations underlying cancer. Functional overexpression of miR-31, the most underexpressed miRNA in serous ovarian cancer, repressed predicted miR-31 gene targets including the cell cycle regulator E2F2. MIR31 and CDKN2A, which encode p14(ARF) and p16(INK4A), are located at 9p21.3, a genomic region commonly deleted in ovarian and other cancers. p14(ARF) promotes p53 activity, and E2F2 overexpression in p53 wild-type cells normally leads via p14(ARF) to an induction of p53-dependent apoptosis. In a number of serous cancer cell lines with a dysfunctional p53 pathway (i.e., OVCAR8, OVCA433, and SKOV3), miR-31 overexpression inhibited proliferation and induced apoptosis; however, in other lines (i.e., HEY and OVSAYO) with functional p53, miR-31 had no effect. Additionally, the osteosarcoma cell line U2OS and the prostate cancer cell line PC3 (p14(ARF)-deficient and p53-deficient, respectively) were also sensitive to miR-31. Furthermore, miR-31 overexpression induced a global gene expression pattern in OVCAR8 associated with better prognosis in tumors from patients with advanced stage serous ovarian cancer, potentially affecting many genes underlying disease progression. Our findings reveal that loss of miR-31 is associated with defects in the p53 pathway and functions in serous ovarian cancer and other cancers, suggesting that patients with cancers deficient in p53 activity might benefit from therapeutic delivery of miR-31.

A Link between mir-100 and FRAP1/mTOR in Clear Cell Ovarian Cancer

Abstract: MicroRNAs (miRNAs) are small noncoding RNAs that direct gene regulation through translational repression and degradation of complementary mRNA. Although miRNAs have been implicated as oncogenes and tumor suppressors in a variety of human cancers, functional roles for individual miRNAs have not been described in clear cell ovarian carcinoma, an aggressive and chemoresistant subtype of ovarian cancer. We performed deep sequencing to comprehensively profile miRNA expression in 10 human clear cell ovarian cancer cell lines compared with normal ovarian surface epithelial cultures and discovered 54 miRNAs that were aberrantly expressed. Because of the critical roles of the phosphatidylinositol 3-kinase/v-akt murine thymoma viral oncogene homolog 1/mammalian target of rapamycin (mTOR) pathway in clear cell ovarian cancer, we focused on mir-100, a putative tumor suppressor that was the most down-regulated miRNA in our cancer cell lines, and its up-regulated target, FRAP1/mTOR. Overexpression of mir-100 inhibited mTOR signaling and enhanced sensitivity to the rapamycin analog RAD001 (everolimus), confirming the key relationship between mir-100 and the mTOR pathway. Furthermore, overexpression of the putative tumor suppressor mir-22 repressed the EVI1 oncogene, which is known to suppress apoptosis by stimulating phosphatidylinositol 3-kinase/v-akt murine thymoma viral oncogene homolog 1 signaling. In addition to these specific effects, reversing the expression of mir-22 and the putative oncogene mir-182 had widespread effects on target and nontarget gene populations that ultimately caused a global shift in the cancer gene signature toward a more normal state. Our experiments have revealed strong candidate miRNAs and their target genes that may contribute to the pathogenesis of clear cell ovarian cancer, thereby highlighting alternative therapeutic strategies for the treatment of this deadly cancer.

Genome engineering uncovers 54 evolutionarily conserved and testis-enriched genes that are not required for male fertility in mice

Abstract: Gene-expression analysis studies from Schultz et al. estimate that more than 2,300 genes in the mouse genome are expressed predominantly in the male germ line. As of their 2003 publication [Schultz N, Hamra FK, Garbers DL (2003) Proc Natl Acad Sci USA 100(21):12201-12206], the functions of the majority of these testis-enriched genes during spermatogenesis and fertilization were largely unknown. Since the study by Schultz et al., functional analysis of hundreds of reproductive-tract-enriched genes have been performed, but there remain many testis-enriched genes for which their relevance to reproduction remain unexplored or unreported. Historically, a gene knockout is the "gold standard" to determine whether a gene's function is essential in vivo. Although knockout mice without apparent phenotypes are rarely published, these knockout mouse lines and their phenotypic information need to be shared to prevent redundant experiments. Herein, we used bioinformatic and experimental approaches to uncover mouse testis-enriched genes that are evolutionarily conserved in humans. We then used gene-disruption approaches, including Knockout Mouse Project resources (targeting vectors and mice) and CRISPR/Cas9, to mutate and quickly analyze the fertility of these mutant mice. We discovered that 54 mutant mouse lines were fertile. Thus, despite evolutionary conservation of these genes in vertebrates and in some cases in all eukaryotes, our results indicate that these genes are not individually essential for male mouse fertility. Our phenotypic data are highly relevant in this fiscally tight funding period and postgenomic age when large numbers of genomes are being analyzed for disease association, and will prevent unnecessary expenditures and duplications of effort by others.

TCTE1 is a conserved component of the dynein regulatory complex and is required for motility and metabolism in mouse spermatozoa

Abstract: Flagella and cilia are critical cellular organelles that provide a means for cells to sense and progress through their environment. The central component of flagella and cilia is the axoneme, which comprises the “9+2” microtubule arrangement, dynein arms, radial spokes, and the nexin-dynein regulatory complex (N-DRC). Failure to properly assemble components of the axoneme leads to defective flagella and in humans leads to a collection of diseases referred to as ciliopathies. Ciliopathies can manifest as severe syndromic diseases that affect lung and kidney function, central nervous system development, bone formation, visceral organ organization, and reproduction. T-Complex-Associated–Testis-Expressed 1 (TCTE1) is an evolutionarily conserved axonemal protein present from Chlamydomonas (DRC5) to mammals that localizes to the N-DRC. Here, we show that mouse TCTE1 is testis-enriched in its expression, with its mRNA appearing in early round spermatids and protein localized to the flagellum. TCTE1 is 498 aa in length with a leucine rich repeat domain at the C terminus and is present in eukaryotes containing a flagellum. Knockout of Tcte1 results in male sterility because Tcte1-null spermatozoa show aberrant motility. Although the axoneme is structurally normal in Tcte1 mutant spermatozoa, Tcte1-null sperm demonstrate a significant decrease of ATP, which is used by dynein motors to generate the bending force of the flagellum. These data provide a link to defining the molecular intricacies required for axoneme function, sperm motility, and male fertility.

PTEN: Multiple Functions in Human Malignant Tumors

Abstract: PTEN is the most important negative regulator of the PI3K signaling pathway. In addition to its canonical, PI3K inhibition-dependent functions, PTEN can also function as a tumor suppressor in a PI3K-independent manner. Indeed, the PTEN network regulates a broad spectrum of biological functions, modulating the flow of information from membrane-bound growth factor receptors to nuclear transcription factors, occurring in concert with other tumor suppressors and oncogenic signaling pathways. PTEN acts through its lipid and protein phosphatase activity and other non-enzymatic mechanisms. Studies conducted over the past 10 years have expanded our understanding of the biological role of PTEN, showing that in addition to its ability to regulate proliferation and cell survival, it also plays an intriguing role in regulating genomic stability, cell migration, stem cell self-renewal and tumor microenvironment. Changes in PTEN protein levels, location, and enzymatic activity through various molecular mechanisms can generate a continuum of functional PTEN levels in inherited syndromes, sporadic cancers and other diseases. PTEN activity can indeed, be modulated by mutations, epigenetic silencing, transcriptional repression, aberrant protein localization, and posttranslational modifications. This review will discuss our current understanding of the biological role of PTEN, how PTEN expression and activity are regulated, and the consequences of PTEN dysregulation in human malignant tumors.

Early detection of lung adenocarcinoma in sputum by a panel of microRNA markers

Abstract: Adenocarcinoma is the most common type of lung cancer, the leading cause of cancer deaths in the world. Early detection is the key to improve the survival of lung adenocarcinoma patients. We have previously shown that microRNAs (miRNAs) were stably present in sputum and could be applied to diagnosis of lung cancer. The aim of our study was to develop a panel of miRNAs that can be used as highly sensitive and specific sputum markers for early detection of lung adenocarcinoma. Our study contained 3 phases: (i) marker discovery using miRNA profiling on paired normal and tumor lung tissues from 20 patients with lung adenocarcinoma; (ii) marker optimization by real-time reverse transcription-quantitative polymerase chain reaction on sputum of a case-control cohort consisting of 36 cancer patients and 36 health individuals and (iii) validation on an independent set of 64 lung cancer patients and 58 cancer-free subjects. From the surgical tissues, 7 miRNAs with significantly altered expression were identified, of which "4" were overexpressed and "3" were underexpressed in all 20 tumors. On the sputum samples of the case-control cohort, 4 (miR-21, miR-486, miR-375 and miR-200b) of the 7 miRNAs were selected, which in combination produced the best prediction in distinguishing lung adenocarcinoma patients from normal subjects with 80.6% sensitivity and 91.7% specificity. Validation of the marker panel in the independent populations confirmed the sensitivity and specificity that provided a significant improvement over any single one alone. The sputum markers demonstrated the potential of translation to laboratory settings for improving the early detection of lung adenocarcinoma.

High-grade serous ovarian cancer: Basic sciences, clinical and therapeutic standpoints

Abstract: Among a litany of malignancies affecting the female reproductive tract, that of the ovary is the most frequently fatal. Moreover, while the steady pace of scientific discovery has fuelled recent ameliorations in the outcomes of many other cancers, the rates of mortality for ovarian cancer have been stagnant since around 1980. Yet despite the grim outlook, progress is being made towards better understanding the fundamental biology of this disease and how its biology in turn influences clinical behaviour. It has long been evident that ovarian cancer is not a unitary disease but rather a multiplicity of distinct malignancies that share a common anatomical site upon presentation. Of these, the high-grade serous subtype predominates in the clinical setting and is responsible for a disproportionate share of the fatalities from all forms of ovarian cancer. This review aims to provide a detailed overview of the clinical-pathological features of ovarian cancer with a particular focus on the high-grade serous subtype. Along with a description of the relevant clinical aspects of this disease, including novel trends in treatment strategies, this text will inform the reader of recent updates to the scientific literature regarding the origin, aetiology and molecular-genetic basis of high-grade serous ovarian cancer (HGSOC).

Control of metastatic progression by microRNA regulatory networks.

Abstract: Aberrant microRNA (miRNA) expression is a defining feature of human malignancy. Specific miRNAs have been identified as promoters or suppressors of metastatic progression. miRNAs control metastasis through divergent or convergent regulation of metastatic gene pathways. Some miRNA regulatory networks govern cell-autonomous cancer phenotypes, whereas others modulate the cell-extrinsic composition of the metastatic microenvironment. The use of small RNAs as probes into the molecular and cellular underpinnings of metastasis holds promise for the identification of candidate genes for potential therapeutic intervention.