Lentivirus-mediated oncogene introduction into mammary cells in vivo induces tumors

Advances in Immunocompetent Mouse and Rat Models

Rodent models of breast cancer have played critical roles in our understanding of breast cancer development and progression as well as preclinical testing of cancer prevention and therapeutics. In this article, we first review the values and challenges of conventional genetically engineered mouse (GEM) models and newer iterations of these models, especially those with inducible or conditional regulation of oncogenes and tumor suppressors. Then, we discuss nongermline (somatic) GEM models of breast cancer with temporospatial control, made possible by intraductal injection of viral vectors to deliver oncogenes or to manipulate the genome of mammary epithelial cells. Next, we introduce the latest development in precision editing of endogenous genes using in vivo CRISPR-Cas9 technology. We conclude with the recent development in generating somatic rat models for modeling estrogen receptor-positive breast cancer, something that has been difficult to accomplish in mice.

Aneuploidy in human cancer: new tools and perspectives

Chromosome copy number imbalances, otherwise known as aneuploidies, are a common but poorly understood feature of cancer. Here, we describe recent advances in both detecting and manipulating aneuploidies that have greatly advanced our ability to study their role in tumorigenesis. In particular, new clustered regularly interspaced short palindromic repeats (CRISPR)-based techniques have been developed that allow the creation of isogenic cell lines with specific chromosomal changes, thereby facilitating experiments in genetically controlled backgrounds to uncover the consequences of aneuploidy. These approaches provide increasing evidence that aneuploidy is a key driver of cancer development and enable the identification of multiple dosage-sensitive genes encoded on aneuploid chromosomes. Consequently, measuring aneuploidy may inform clinical prognosis, while treatment strategies that target aneuploidy could represent a novel method to counter malignant growth.

In Vivo Gene Delivery into Mouse Mammary Epithelial Cells Through Mammary Intraductal Injection

Mouse mammary glands comprise ductal trees, which are lined by epithelial cells and have one opening at the tip of each nipple. The epithelial cells play a major role in mammary gland function and are the origin of most mammary tumors. Introducing genes of interest into mouse mammary epithelial cells is a critical step in evaluating gene function in epithelial cells and generating mouse mammary tumor models. This goal can be accomplished through the intraductal injection of a viral vector carrying the genes of interest into the mouse mammary ductal tree. The injected virus subsequently infects mammary epithelial cells, bringing in the genes of interest. The viral vector can be lentiviral, retroviral, adenoviral, or adenovirus-associated viral (AAV). This study demonstrates how a gene of interest is delivered into mammary epithelial cells through mouse mammary intraductal injection of a viral vector. A lentivirus carrying GFP is used to show stable expression of a delivered gene, and a retrovirus carrying Erbb2 (HER2/Neu) is used to demonstrate oncogene-induced atypical hyperplastic lesions and mammary tumors.

Targeting HECTD3-IKKα axis inhibits inflammation-related metastasis

Metastasis is the leading cause of cancer-related death. The interactions between circulating tumor cells and endothelial adhesion molecules in distant organs is a key step during extravasation in hematogenous metastasis. Surgery is a common intervention for most primary solid tumors. However, surgical trauma-related systemic inflammation facilitates distant tumor metastasis by increasing the spread and adhesion of tumor cells to vascular endothelial cells (ECs). Currently, there are no effective interventions to prevent distant metastasis. Here, we show that HECTD3 deficiency in ECs significantly reduces tumor metastasis in multiple mouse models. HECTD3 depletion downregulates expression of adhesion molecules, such as VCAM-1, ICAM-1 and E-selectin, in mouse primary ECs and HUVECs stimulated by inflammatory factors and inhibits adhesion of tumor cells to ECs both in vitro and in vivo. We demonstrate that HECTD3 promotes stabilization, nuclear localization and kinase activity of IKKα by ubiquitinating IKKα with K27- and K63-linked polyubiquitin chains at K296, increasing phosphorylation of histone H3 to promote NF-κB target gene transcription. Knockout of HECTD3 in endothelium significantly inhibits tumor cells lung colonization, while conditional knockin promotes that. IKKα kinase inhibitors prevented LPS-induced pulmonary metastasis. These findings reveal the promotional role of the HECTD3-IKKα axis in tumor hematogenous metastasis and provide a potential strategy for tumor metastasis prevention.

Targeting the Pro-Survival Protein BCL-2 to Prevent Breast Cancer

Current chemopreventive strategies require 3-5 years of continuous treatment and have the concerns of significant side effects; therefore, new chemopreventive agents that require shorter and safer treatments are urgently needed. In this study, we developed a new murine model of breast cancer that mimics human breast cancer initiation and is ideal for testing the efficacy of chemopreventive therapeutics. In this model, introduction of lentivirus carrying a PIK3CA gene mutant commonly found in breast cancers infects a small number of the mammary cells, leading to atypia first and then to ductal carcinomas that are positive for both estrogen receptor and progesterone receptor. Venetoclax is a BH3 mimetic that blocks the anti-apoptotic protein BCL-2 and has efficacy in treating breast cancer. We found that venetoclax treatment of atypia-bearing mice delayed the progression to tumors, improved overall survival, and reduced pulmonary metastasis. Therefore, prophylactic treatment to inhibit the pro-survival protein BCL-2 may provide an alternative to the currently available regimens in breast cancer prevention.

Single-cell evaluation reveals shifts in the tumor-immune niches that shape and maintain aggressive lesions in the breast

There is an unmet clinical need for stratification of breast lesions as indolent or aggressive to tailor treatment. Here, single-cell transcriptomics and multiparametric imaging applied to a mouse model of breast cancer reveals that the aggressive tumor niche is characterized by an expanded basal-like population, specialization of tumor subpopulations, and mixed-lineage tumor cells potentially serving as a transition state between luminal and basal phenotypes. Despite vast tumor cell-intrinsic differences, aggressive and indolent tumor cells are functionally indistinguishable once isolated from their local niche, suggesting a role for non-tumor collaborators in determining aggressiveness. Aggressive lesions harbor fewer total but more suppressed-like T cells, and elevated tumor-promoting neutrophils and IL-17 signaling, disruption of which increase tumor latency and reduce the number of aggressive lesions. Our study provides insight into tumor-immune features distinguishing indolent from aggressive lesions, identifies heterogeneous populations comprising these lesions, and supports a role for IL-17 signaling in aggressive progression.

Advances in Rodent Models for Breast Cancer Formation, Progression, and Therapeutic Testing

Breast cancer is a highly complicated disease. Advancement in the treatment and prevention of breast cancer lies in elucidation of the mechanism of carcinogenesis and progression. Rodent models of breast cancer have developed into premier tools for investigating the mechanisms and genetic pathways in breast cancer progression and metastasis and for developing and evaluating clinical therapeutics. Every rodent model has advantages and disadvantages, and the selection of appropriate rodent models with which to investigate breast cancer is a key decision in research. Design of a suitable rodent model for a specific research purpose is based on the integration of the advantages and disadvantages of different models. Our purpose in writing this review is to elaborate on various rodent models for breast cancer formation, progression, and therapeutic testing.

Intraductal Injection of Lentivirus Vectors for Stably Introducing Genes into Rat Mammary Epithelial Cells in Vivo

Various retroviral and lentiviral vectors have been used for up-the-teat intraductal injection to deliver markers, oncogenes, and other genes into mammary epithelial cells in mice. These methods along with the large number of genetically engineered mouse lines have greatly helped us learn normal breast development and tumorigenesis. Rats are also valuable models for studying human breast development and cancer. However, genetically engineered rats are still uncommon, and previous reports of intraductal injection of retroviral vectors into rats appear to be inefficient in generating mammary tumors. Here, we report, and describe the method for, stably introducing marker genes and oncogenes into mammary glands in rats using intraductal injection of commonly used lentiviral vectors. This method can infect mammary epithelial cells efficiently, and the infected cells can initiate tumorigenesis, including estrogen receptor-positive and hormone-dependent tumors, which are the most common subtype of human breast cancer but are yet still difficult to model in mice. This technique provides another tool for studying formation, prevention, and treatment of breast cancer, especially estrogen receptor-positive breast cancer.

Mammary Precancerous Stem and Non-Stem Cells Evolve into Cancers of Distinct Subtypes

There are distinct cell subpopulations in normal epithelial tissue, including stem cells, progenitor cells, and more differentiated cells, all of which have been extensively studied for their susceptibility to tumorigenesis. However, normal cells usually have to progress through a precancerous lesion state before becoming a full-blown tumor. Precancerous early lesions are heterogeneous, and the cell subset that is the primary source of the eventual tumor remains largely unknown. By using mouse models that are tailored to address this question, we identified a keratin 6a-expressing precancerous stem cell (PcSC) subset and a more differentiated whey acidic protein-positive (WAP+) cell subset in mammary precancerous lesions initiated by the Wnt1 oncogene. Both cell subsets rapidly progressed to cancer upon introduction of constitutively active versions of either HRAS or BRAF. However, the resulting tumors were dramatically different in protein profiles and histopathology: keratin 6a+ precancerous cells gave rise to adenocarcinoma, whereas WAP+ cells yielded metaplastic carcinoma with severe squamous differentiation and more robust activation of MEK/ERK signaling. Therefore, both stem and non-stem cells in mammary precancerous lesions can contribute to the eventual cancers, but their differentiation status determines the resulting cancer phenotype. This work identifies a previously unknown player in cancer heterogeneity and suggests that cancer prevention should target precancerous cells broadly and not be limited to PcSC. SIGNIFICANCE: This work uses a novel mouse mammary gland cancer model to show that tumors initiated from different precancerous mammary epithelial cells are distinct.

Krüpple-like factor 5 is essential for mammary gland development and tumorigenesis

Krüpple-like factor 5 (KLF5) is required for the development of the embryo and multiple organs, such as the lung and intestine. KLF5 plays a pro-proliferative and oncogenic role in several carcinomas, including breast cancer. However, its role in normal mammary gland development and oncogenesis has not been elucidated in vivo. In this study, we used mammary gland-specific Klf5 conditional knockout mice derived by mating Klf5-LoxP and MMTV-Cre mice. The genetic ablation of Klf5 suppresses mammary gland ductal elongation and lobuloalveolar formation. Klf5 deficiency inhibits mammary epithelial cell proliferation, survival, and stem cell maintenance. Klf5 promotes mammary stemness, at least partially, by directly promoting the transcription of Slug. Finally, Klf5 depletion suppressed PyMT-induced mammary gland tumor cell stemness, tumor initiation, and growth in vivo. Slug also mediated these functions of Klf5 in vivo. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Comparative analysis and optimization of protocols for producing recombinant lentivirus carrying the anti-Her2 chimeric antigen receptor gene

BACKGROUND

The production of anti-Her2 chimeric antigen receptor (CAR) T cells needs to be optimized to make it a reliable therapy.

METHODS

Three types of lentiviral vectors expressing anti-Her2 CAR together with packaging plasmids were co-transfected into 293 T-17 cells. The vector with the best packaging efficiency was selected, and the packaging cell culture system and packaging plasmid system were optimized. Centrifugation speed was optimized for the concentration of lentivirus stock. The various purification methods used included membrane filtration, centrifugation with a sucrose cushion and the novelly-designed instantaneous high-speed centrifugation. The recombinant lentiviruses were transduced into human peripheral T cells with an optimized multiplicity of infection (MOI). CAR expression levels by three vectors and the efficacy of CAR-T cells were compared.

RESULTS

When co-transfected, packaging cells in suspension were better than the commonly used adherent culture condition, with the packaging system psPAX2/pMD2.G being better than pCMV-dR8.91/pVSV-G. The optimal centrifugation speed for concentration was 20 000 g, rather than the generally used ultra-speed. Importantly, adding instantaneous centrifugation for purification significantly increased human peripheral T cell viability (from 13.25% to 62.80%), which is a technical breakthrough for CAR-T cell preparation. The best MOI value for transducing human peripheral T cells was 40. pLVX-EF1a-CAR-IRES-ZsGreen1 expressed the highest level of CAR in human peripheral T cells and the cytotoxicity of CAR-T cells reached 63.56%.

CONCLUSIONS

We optimized the preparation of recombinant lentivirus that can express third-generation anti-Her2 CAR in T cells, which should lay the foundation for improving the efficacy of CAR-T cells with respect to killing target cells.

Continuous cell supply from Krt7-expressing hematopoietic stem cells during native hematopoiesis revealed by targeted in vivo gene transfer method

The nature of hematopoietic stem cells under normal hematopoiesis remained largely unknown due to the limited assays available to monitor their behavior in situ. Here, we develop a new mouse model to transfer genes specifically into the primitive hematopoietic stem cell compartment through the utilization of a modified Rcas/TVA system. We succeeded in transferring a GFP reporter gene into adult hematopoietic stem cells in vivo, which are predominantly quiescent, by generating pseudotyped-lentivirus. Furthermore, we demonstrate the utility of this system to study neonatal hematopoiesis, a developmental stage that has been difficult to analyze to date. Using the system developed in this study, we observed continuous multi-lineage hematopoietic cell supply in peripheral blood from Krt7-positive hematopoietic stem cells during unperturbed homeostatic condition. This powerful experimental system could provide a new standard tool to analyze hematopoiesis under physiological condition without transplantation.

A Versatile Gene Delivery System for Efficient and Tumor Specific Gene Manipulation in vivo

The Replication-Competent Avian Sarcoma-leukosis virus long-terminal repeat with splice acceptor (RCAS)-Tumor Virus A (TVA) gene delivery system has been created based on the fact that avian sarcoma leukosis virus subgroup A only infects cells expressing its receptor, TVA. This system has been successfully applied to create various mouse models for human cancers. Here we briefly discuss the advantages and the potential caveats of using this RCAS-TVA gene delivery system in cancer research. We also introduce and discuss how our newly designed RCAS-based gene delivery system (RCI-Oncogene, for RCAS-Cre-IRES-Oncogene) allows concise and efficient manipulation of gene expression in tumors in vivo, and how this system can be used to rapidly study the biological function of gene(s) and/or the collaborative actions of multiple genes in regulating tumor initiation, progression and/or metastasis.

Applications of the CRISPR/Cas9 system in murine cancer modeling

Advanced biological technologies allowing for genetic manipulation of the genome are increasingly being used to unravel the molecular pathogenesis of human diseases. The clustered regulatory interspaced short palindromic repeat/CRISPR-associated protein (CRISPR/Cas) technology started a revolution of this field owing to its flexibility and relative ease of use. Recently, application of the CRISPR/Cas9 system has been extended to in vivo approaches, leveraging its potential for human disease modeling. Particularly in oncological research, where genetic defects in somatic cells are tightly linked to etiology and pathological phenotypes, the CRISPR/Cas technology is being used to recapitulate various types of genetic aberrations. Here we review murine cancer models that have been developed via combining the CRISPR/Cas9 technology with in vivo somatic gene transfer approaches. Exploiting these methodological advances will further accelerate detailed investigations of tumor etiology and treatment.

The PR status of the originating cell of ER/PR-negative mouse mammary tumors

Progesterone receptor (PR) is usually co-localized with estrogen receptor (ER) in normal mammary cells. It is not known whether ER/PR-negative human breast cancer arises from an ER/PR-negative cell or from an ER/PR-positive cell that later lost ER/PR. Using intraductal injection of a lentivirus to deliver both an oncogene (ErbB2) and a floxed green fluorescent protein (GFP) in PR(Cre/+)mice, whose Cre gene is under the control of the PR promoter, we were able to trace the PR status of the infected cells as they progressed to cancer. We found that the resulting early lesions stained negative for PR in most of the cells and usually retained GFP. The resulting tumors lacked ER and PR, and 75% (15/20) of them retained the GFP signal in all tumor cells, suggesting PR was never expressed throughout the evolution of a majority of these tumors. In conclusion, our data demonstrate that ErbB2-initiated ER/PR-negative mammary tumors primarily originate from the subset of the mammary epithelium that is negative for PR and probably ER as well. These findings also provide an explanation for why antihormonal therapy fails to prevent ER-negative breast cancers.

Transformation of enriched mammary cell populations with polyomavirus middle T antigen influences tumor subtype and metastatic potential

INTRODUCTION

Breast cancer exhibits significant molecular, histological, and pathological diversity. Factors that impact this heterogeneity are poorly understood; however, transformation of distinct normal cell populations of the breast may generate different tumor phenotypes. Our previous study demonstrated that the polyomavirus middle T antigen (PyMT) oncogene can establish diverse tumor subtypes when broadly expressed within mouse mammary epithelial cells. In the present study, we assessed the molecular, histological, and metastatic outcomes in distinct mammary cell populations transformed with the PyMT gene.

METHODS

Isolated mouse mammary epithelial cells were transduced with a lentivirus encoding PyMT during an overnight infection and then sorted into hormone receptor-positive luminal (CD133+), hormone receptor-negative luminal (CD133-), basal, and stem cell populations using the cell surface markers CD24, CD49f, and CD133. Each population was subsequently transplanted into syngeneic cleared mouse mammary fat pads to generate tumors. Tumors were classified by histology, estrogen receptor status, molecular subtype, and metastatic potential to investigate whether transformation of different enriched populations affects tumor phenotype.

RESULTS

Although enriched mammary epithelial cell populations showed no difference in either the ability to form tumors or tumor latency, differences in prevalence of solid adenocarcinomas and squamous, papillary, and sebaceous-like tumors were observed. In particular, squamous metaplasia was observed more frequently in tumors derived from basal and stem cells than in luminal cells. Interestingly, both molecularly basal and luminal tumors developed from luminal CD133+, basal, and stem cell populations; however, luminal CD133- cells gave rise exclusively to molecularly basal tumors. Tumors arising from the luminal CD133-, basal, and stem cell populations were highly metastatic; however, luminal CD133+ cells generated tumors that were significantly less metastatic, possibly due to an inability of these tumor cells to escape the primary tumor site.

CONCLUSIONS

Expression of PyMT within different mammary cell populations influences tumor histology, molecular subtype, and metastatic potential. The data demonstrate that luminal CD133+ cells give rise to less metastatic tumors, luminal CD133- cells preferentially establish basal tumors, and the cell of origin for squamous metaplasia likely resides in the basal and stem cell populations.

Glioma initiating cells contribute to malignant transformation of host glial cells during tumor tissue remodeling via PDGF signaling

INTRODUCTION

Glioma initiating cells (GICs) play important roles in tumor initiation and progression. However, interactions between tumor cells and host cells of local tumor microenvironment are kept largely unknown. Besides GICs and their progeny cells, whether adjacent normal glial cells contribute to tumorigenesis during glioma tissue remodeling deserves further investigation.

METHODS

Red fluorescence protein (RFP) gene was stably transfected into human GIC cells lines SU3 and U87, then were transplanted intracerebrally into athymic nude mice with whole-body green fluorescence protein (GFP) expression. The interactions between GICs and host cells in vivo were observed during tissue remodeling processes initiated by hGICs. The biological characteristics of host glial cells with high proliferation capability cloned from the xenograft were further assayed.

RESULTS

In a SU3 initiated dual-fluorescence xenograft glioma model, part of host cells cloned from the intracerebral tumors were found acquiring the capability of unlimited proliferation. PCR and FISH results indicated that malignant transformed cells were derived from host cells; cell surface marker analysis showed these cells expressed murine oligodendrocyte specific marker CNP, and oligodendrocyte progenitor cells (OPCs) specific markers PDGFR-α and NG2. Chromosomal analysis showed these cells were super tetraploid. In vivo studies showed they behaved with high invasiveness activity and nearly 100% tumorigenic ratio. Compared with SU3 cells with higher PDGF-B expression, GICs derived from U87 cells with low level of PDGF-B expression failed to induce host cell transformation.

CONCLUSIONS

Primary high invasive GICs SU3 contribute to transformation of adjacent normal host glial cells in local tumor microenvironment possibly via PDGF/PDGFR signaling activation, which deserved further investigation.

Generation and characterization of a breast carcinoma model by PyMT overexpression in mammary epithelial cells of tree shrew, an animal close to primates in evolution

The tree shrew is becoming an attractive experimental animal model for human breast cancer owing to a closer relationship to primates/humans than rodents. Tree shrews are superior to classical primates because tree shrew are easier to manipulate, maintain and propagate. It is required to establish a high-efficiency tree shrew breast cancer model for etiological research and drug assessment. Our previous studies suggest that 7,12-dimethylbenz(a)anthracene (DMBA) and medroxyprogesterone acetate (MPA) induce breast tumors in tree shrews with a low frequency (<50%) and long latency (∼ 7-month), making these methods less than ideal. We induced mammary tumors in tree shrew (Tupaia belangeri chinensis) by injection of lentivirus expressing the PyMT oncogene into mammary ducts of 22 animals. Most tree shrews developed mammary tumors with a latency of about three weeks, and by 7 weeks all injected tree shrews had developed mammary tumors. Among these, papillary carcinoma is the predominant tumor type. One case showed lymph node and lung metastasis. Interestingly, the expression levels of phosphorylated AKT, ERK and STAT3 were elevated in 41-68% of PyMT-induced mammary tumors, but not all tumors. Finally, we observed that the growth of PyMT-induced tree shrew mammary tumors was significantly inhibited by Cisplatin and Epidoxorubicin. PyMT-induced tree shrew mammary tumor model may be suitable for further breast cancer research and drug development, due to its high efficiency and short latency.

A versatile modular vector system for rapid combinatorial mammalian genetics

Here, we describe the multiple lentiviral expression (MuLE) system that allows multiple genetic alterations to be introduced simultaneously into mammalian cells. We created a toolbox of MuLE vectors that constitute a flexible, modular system for the rapid engineering of complex polycistronic lentiviruses, allowing combinatorial gene overexpression, gene knockdown, Cre-mediated gene deletion, or CRISPR/Cas9-mediated (where CRISPR indicates clustered regularly interspaced short palindromic repeats) gene mutation, together with expression of fluorescent or enzymatic reporters for cellular assays and animal imaging. Examples of tumor engineering were used to illustrate the speed and versatility of performing combinatorial genetics using the MuLE system. By transducing cultured primary mouse cells with single MuLE lentiviruses, we engineered tumors containing up to 5 different genetic alterations, identified genetic dependencies of molecularly defined tumors, conducted genetic interaction screens, and induced the simultaneous CRISPR/Cas9-mediated knockout of 3 tumor-suppressor genes. Intramuscular injection of MuLE viruses expressing oncogenic H-RasG12V together with combinations of knockdowns of the tumor suppressors cyclin-dependent kinase inhibitor 2A (Cdkn2a), transformation-related protein 53 (Trp53), and phosphatase and tensin homolog (Pten) allowed the generation of 3 murine sarcoma models, demonstrating that genetically defined autochthonous tumors can be rapidly generated and quantitatively monitored via direct injection of polycistronic MuLE lentiviruses into mouse tissues. Together, our results demonstrate that the MuLE system provides genetic power for the systematic investigation of the molecular mechanisms that underlie human diseases.

MicroRNA-205 signaling regulates mammary stem cell fate and tumorigenesis

Dysregulation of epigenetic controls is associated with tumorigenesis in response to microenvironmental stimuli; however, the regulatory pathways involved in epigenetic dysfunction are largely unclear. We have determined that a critical epigenetic regulator, microRNA-205 (miR-205), is repressed by the ligand jagged1, which is secreted from the tumor stroma to promote a cancer-associated stem cell phenotype. Knockdown of miR-205 in mammary epithelial cells promoted epithelial-mesenchymal transition (EMT), disrupted epithelial cell polarity, and enhanced symmetric division to expand the stem cell population. Furthermore, miR-205-deficient mice spontaneously developed mammary lesions, while activation of miR-205 markedly diminished breast cancer stemness. These data provide evidence that links tumor microenvironment and microRNA-dependent regulation to disruption of epithelial polarity and aberrant mammary stem cell division, which in turn leads to an expansion of stem cell population and tumorigenesis. This study elucidates an important role for miR-205 in the regulation of mammary stem cell fate, suggesting a potential therapeutic target for limiting breast cancer genesis.

Simplified production and concentration of lentiviral vectors to achieve high transduction in primary human T cells

Background

Lentiviral vectors have emerged as efficient vehicles for transgene delivery in both dividing and non-dividing cells. A number of different modifications in vector design have increased biosafety and transgene expression. However, despite these advances, the transduction of primary human T cells is still challenging and methods to achieve efficient gene transfer are often expensive and time-consuming.

Results

Here we present a simple optimised protocol for the generation and transduction of lentivirus in primary human CD45RA⁺ T cells. We show that generation of high-titre lentivirus with improved primary T cell transduction is dependent upon optimised ultracentrifuge speed during viral concentration. Moreover, we demonstrate that transduction efficiency can be increased with simple modifications to the culturing conditions. Overall, a transduction efficiency of up to 89% in primary human CD45RA⁺ cells is achievable when these modifications are used in conjunction.

Conclusion

The optimised protocol described here is easy to implement and should facilitate the production of high-titre lentivirus with superior transduction efficiency in primary human T cells without the need for further purification methods.

Accelerating cancer modeling with RNAi and nongermline genetically engineered mouse models

For more than two decades, genetically engineered mouse models have been key to our mechanistic understanding of tumorigenesis and cancer progression. Recently, the massive quantity of data emerging from cancer genomics studies has demanded a corresponding increase in the efficiency and throughput of in vivo models for functional testing of putative cancer genes. Already a mainstay of cancer research, recent innovations in RNA interference (RNAi) technology have extended its utility for studying gene function and genetic interactions, enabling tissue-specific, inducible and reversible gene silencing in vivo. Concurrent advances in embryonic stem cell (ESC) culture and genome engineering have accelerated several steps of genetically engineered mouse model production and have facilitated the incorporation of RNAi technology into these models. Here, we review the current state of these technologies and examine how their integration has the potential to dramatically enhance the throughput and capabilities of animal models for cancer.

Dinosaurs and ancient civilizations: reflections on the treatment of cancer

Research efforts in the area of palaeopathology have been seen as an avenue to improve our understanding of the pathogenesis of cancer. Answers to questions of whether dinosaurs had cancer, or if cancer plagued ancient civilizations, have captured the imagination as well as the popular media. Evidence for dinosaurian cancer may indicate that cancer may have been with us from the dawn of time. Ancient recorded history suggests that past civilizations attempted to fight cancer with a variety of interventions. When contemplating the issue why a generalized cure for cancer has not been found, it might prove useful to reflect on the relatively limited time that this issue has been an agenda item of governmental attention as well as continued introduction of an every evolving myriad of manmade carcinogens relative to the total time cancer has been present on planet Earth. This article reflects on the history of cancer and the progress made following the initiation of the "era of cancer chemotherapy."

Genetic manipulation of individual somatic mammary cells in vivo reveals a master role of STAT5a in inducing alveolar fate commitment and lactogenesis even in the absence of ovarian hormones

Assessing the molecular control of development and cell fate in individual cells in the intact mammary epithelium has not been possible to date. By exploiting an intraductal retrovirus (RCAS)-mediated gene delivery method to introduce a marker gene, we found that ductal epithelial cells are turned over with a half time of approximately 1month in adult virgin mice. However, following RCAS-mediated introduction of a constitutively activated STAT5a (caSTAT5a), caSTAT5a-activated ductal epithelial cells expand and replace other cells in the epithelium, eventually forming a mammary gland resembling that in a late pregnant mouse, suggesting that STAT5a activation alone is sufficient to mediate pregnancy-induced mammary cell expansion, alveolar cell fate commitment, and lactogenesis. Furthermore, such caSTAT5a-induced alveolar differentiation does not require ovarian functions, although caSTAT5a-induced cell proliferation is partly reduced in ovariectomized mice. In conclusion, in this first report of studying the developmental role of a gene in a few cells in a normally developed virgin mammary ductal tree, STAT5a activation causes alveolar fate commitment and lactogenesis, and with the help of ovarian hormones, drives alveolar expansion.

The War on Cancer rages on

In 1971, the "War on Cancer" was launched by the US government to cure cancer by the 200-year anniversary of the founding of the United States of America, 1976. This article briefly looks back at the progress that has been made in cancer research and compares progress made in other areas of human affliction. While progress has indeed been made, the battle continues to rage on.

Lentivirus vectors for stably introducing genes into mammary epithelial cells in vivo

We have reported the use of vectors based on avian leukosis virus (ALV) and ALV env pseudotyped lentivirus for stably introducing genes into somatic mammary cells in vivo for tumor modeling. These vectors require tva transgenic mice for viral infection. Here, we report, and described the method for, stably introducing genes into the mammary gland in mice using intraductal injection of a common lentiviral vector. This method does not need tva-transgenic mice for infection. This in vivo transformation method may be useful for rapid testing of the tumorigenic potential of genes potentially involved in breast carcinogenesis.

The RCAS-TVA system for introduction of oncogenes into selected somatic mammary epithelial cells in vivo

We have reported the use of the RCAS-TVA system to model sporadic tumorigenesis upon oncogenic activation in somatic mammary epithelial cells in the mouse. Here we review the advantages of this approach as compared to conventional mouse models with transgenic oncogene expression. We also in detail describe the RCAS-TVA method for introducing genes into somatic mammary epithelial cells engineered to express the avian receptor tva. This method may be particularly useful in modeling oncogenic activation and subsequent tumorigenesis in distinct breast epithelial cell sub-populations, including progenitor cells.

Lessons in signaling and tumorigenesis from polyomavirus middle T antigen

The small DNA tumor viruses have provided a very long-lived source of insights into many aspects of the life cycle of eukaryotic cells. In recent years, the emphasis has been on cancer-related signaling. Here we review murine polyomavirus middle T antigen, its mechanisms, and its downstream pathways of transformation. We concentrate on the MMTV-PyMT transgenic mouse, one of the most studied models of breast cancer, which permits the examination of in situ tumor progression from hyperplasia to metastasis.

The Par3/aPKC interaction is essential for end bud remodeling and progenitor differentiation during mammary gland morphogenesis

Mammalian polarity proteins have been studied predominantly in cell culture systems, and little is known about their functions in vivo. To address this issue, we used a shRNA lentiviral system to manipulate gene expression in mouse mammary stem/progenitor cells. Transplantation of Par3-depleted stem/progenitor cells into the mammary fat pad severely disrupted mammary development, and glands were characterized by ductal hyperplasia, luminal filling, and highly disorganized end bud structures that were unable to remodel into normal ductal structures. Unexpectedly, Par3-depleted mammary glands also had an expanded progenitor population. We identified a novel function for the atypical protein kinase C (aPKC)-binding domain of Par3 in restricting Par3 and aPKC to the apical region in mammary epithelia in vivo, and found that mammary morphogenesis is dependent on the ability of Par3 to directly bind aPKC. These results reveal a new function for Par3 in the regulation of progenitor differentiation and epithelial morphogenesis in vivo and demonstrate for the first time an essential requirement for the Par3-aPKC interaction.

Neoplasia: the second decade

This issue marks the end of the 10-year anniversary of Neoplasia where we have seen exciting growth in both number of submitted and published articles in Neoplasia. Neoplasia was first published in 1999. During the past 10 years, Neoplasia has dynamically adapted to the needs of the cancer research community as technologies have advanced. Neoplasia is currently providing access to articles through PubMed Central to continue to facilitate rapid broad-based dissemination of published findings to the scientific community through an Open Access model. This has in part helped Neoplasia to achieve an improved impact factor this past year, demonstrating that the manuscripts published by Neoplasia are of great interest to the overall cancer research community. This past year, Neoplasia received a record number of articles for review and has had a 21% increase in the number of published articles.

Lessons from polyoma middle T antigen on signaling and transformation: A DNA tumor virus contribution to the war on cancer

Middle T antigen (MT) is the principal oncogene of murine polyomavirus. Its study has led to the discovery of the roles of tyrosine kinase and phosphoinositide 3-kinase (PI3K) signaling in mammalian growth control and transformation. MT is necessary for viral transformation in tissue culture cells and tumorigenesis in animals. When expressed alone as a transgene, MT causes tumors in a wide variety of tissues. It has no known catalytic activity, but rather acts by assembling cellular signal transduction molecules. Protein phosphatase 2A, protein tyrosine kinases of the src family, PI3K, phospholipase Cgamma1 as well as the Shc/Grb2 adaptors are all assembled on MT. Their activation sets off a series of signaling cascades. Analyses of virus mutants as well as transgenic animals have demonstrated that the effects of a given signal depend not only tissue type, but on the genetic background of the host animal. There remain many opportunities as we seek a full molecular understanding of MT and apply some of its lessons to human cancer.