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We have investigated the potential of the GTP synthesis pathways as chemotherapeutic targets in the human pathogen Cryptococcus neoformans, a common cause of fatal fungal meningoencephalitis. We find that de novo GTP biosynthesis, but not the alternate salvage pathway, is critical to cryptococcal dissemination and survival in vivo. Loss of inosine monophosphate dehydrogenase (IMPDH) in the de novo pathway results in slow growth and virulence factor defects, while loss of the cognate phosphoribosyltransferase in the salvage pathway yielded no phenotypes. Further, the Cryptococcus species complex displays variable sensitivity to the IMPDH inhibitor mycophenolic acid, and we uncover a rare drug-resistant subtype of C. gattii that suggests an adaptive response to microbial IMPDH inhibitors in its environmental niche. We report the structural and functional characterization of IMPDH from Cryptococcus, revealing insights into the basis for drug resistance and suggesting strategies for the development of fungal-specific inhibitors. The crystal structure reveals the position of the IMPDH moveable flap and catalytic arginine in the open conformation for the first time, plus unique, exploitable differences in the highly conserved active site. Treatment with mycophenolic acid led to significantly increased survival times in a nematode model, validating de novo GTP biosynthesis as an antifungal target in Cryptococcus.

Although human breast development is mediated by hormonal and non-hormonal means, the mechanisms that regulate breast progenitor cell activity remain to be clarified. This limited understanding of breast progenitor cells has been due in part to the lack of appropriate model systems to detect and characterize their properties. To examine the effects of WNT signaling and TBX3 expression on progenitor activity in the breast, primary human mammary epithelial cells (MEC) were isolated from reduction mammoplasty tissues and transduced with lentivirus to overexpress WNT1 or TBX3 or reduce expression of their cognate receptors using shRNA. Changes in progenitor activity were quantified using characterized assays. We identified WNT family members expressed by cell populations within the epithelium and assessed alterations in expression of WNT family ligands by MECs in response to TBX3 overexpression and treatment with estrogen and progesterone. Growth of MECs on collagen gels resulted in the formation of distinct luminal acinar and basal ductal colonies. Overexpression of TBX3 in MECs resulted in increased ductal colonies, while shTBX3 expression diminished both colony types. Increased WNT1 expression led to enhanced acinar colony formation, shLRP6 decreased both types of colonies. Estrogen stimulated the formation of acinar colonies in control MEC, but not shLRP6 MEC. Formation of ductal colonies was enhanced in response to progesterone. However, while shLRP6 decreased MEC responsiveness to progesterone, shTBX3 expression did not alter this response. We identified two phenotypically distinguishable lineage-committed progenitor cells that contribute to different structural elements and are regulated via hormonal and non-hormonal mechanisms. WNT signaling regulates both types of progenitor activity. Progesterone favors the expansion of ductal progenitor cells, while estrogen stimulates the expansion of acinar progenitor cells. Paracrine WNT signaling is stimulated by estrogen and progesterone, while autocrine WNT signaling is induced by the embryonic T-box transcription factor TBX3.

During the formation of breast cancer, many genes become altered as cells evolve progressively from normal to a pre-malignant to a malignant state of growth. How mutations in genes lead to specific subtypes of human breast cancer is only partially understood. Here we review how initial genetic or epigenetic alterations within mammary epithelial cells (MECs) can alter cell fate decisions and put pre-malignant cells on a path towards cancer development with specific phenotypes. Understanding the early stages of breast cancer initiation and progression and how normal developmental processes are hijacked during transformation has significant implications for improving early detection and prevention of breast cancer. In addition, insights gleaned from this understanding may also be important for developing subtype-specific treatment options.

The protein tyrosine phosphatase receptor J, PTPRJ, is a tumor suppressor gene that has been implicated in a range of cancers, including breast cancer, yet little is known about its role in normal breast physiology or in mammary gland tumorigenesis. In this paper we show that PTPRJ mRNA is expressed in normal breast tissue and reduced in corresponding tumors. Meta-analysis revealed that the gene encoding PTPRJ is frequently lost in breast tumors and that low expression of the transcript associated with poorer overall survival at 20 years. Immunohistochemistry of PTPRJ protein in normal human breast tissue revealed a distinctive apical localisation in the luminal cells of alveoli and ducts. Qualitative analysis of a cohort of invasive ductal carcinomas revealed retention of normal apical PTPRJ localization where tubule formation was maintained but that tumors mostly exhibited diffuse cytoplasmic staining, indicating that dysregulation of localisation associated with loss of tissue architecture in tumorigenesis. The murine ortholog, Ptprj, exhibited a similar localisation in normal mammary gland, and was differentially regulated throughout lactational development, and in an in vitro model of mammary epithelial differentiation. Furthermore, ectopic expression of human PTPRJ in HC11 murine mammary epithelial cells inhibited dome formation. These data indicate that PTPRJ may regulate differentiation of normal mammary epithelia and that dysregulation of protein localisation may be associated with tumorigenesis.

Osteosarcoma affects both adolescents and adults, and some improvement in the survival rate for affected patients has been reached in the last decade. Still, non-specificity and systemic toxicity may limit traditional therapeutic approaches to some extent. The insulin growth factor 1 (IGF1) and its binding protein (IGFBP3) have been implicated in the tumorigenesis. Nanoparticles, such as graphene oxide (GO), can provide an effective treatment for cancer as they can specifically target cancer cells while reducing undesired side effects. This study aimed to evaluate the toxicity of GO on osteosarcoma in vitro using tumor cell lines with and without knocking out the IGF and IGFBP3 genes. Human osteosarcoma cell lines, U2OS and SAOS2, and the normal osteoblast cell line hFOB1.19 were used. The IGF1 and IGFBP3 genes were eliminated using CRISPR/Cas9. Tumor cells were cultured and treated with GO. Apoptosis and reactive oxygen species (ROS) were analyzed by Annexin V-FITC and ROS assays. The nuclear factor erythroid 2-related factor 2 (NRF2), which is a crucial regulator of cellular resistance to oxidants, was investigated by Western blotting. We found a significantly higher rate of apoptosis in the OS than hFOB1.19, especially in U2OS cells in which IGF1 and IGFBP3 were knocked out. ROS increase due to GO exposure was remarkably time and concentration-dependent. Based on the rate of apoptosis, ROS, Nrf-2 decrease, and cytomorphological changes, GO has a significant cytotoxic effect against OS. Targeting the IGF1 and IGFBP3 signaling pathway may strengthen GO-related cytotoxicity with the potential to increase the survival of patients affected by this tumor.

Disruption of the breast cancer susceptibility gene BRCA2 is associated with increased risk of developing breast and ovarian cancer. Over 1800 sequence changes in BRCA2 have been reported, although for many the pathogenicity is unclear. Classifying these changes remains a challenge, as they may disrupt regulatory sequences as well as the primary protein coding sequence. Sequence changes located in the splice site consensus sequences often disrupt splicing, however sequence changes located within exons are also able to alter splicing patterns. Unfortunately, the presence of these exonic splicing enhancers (ESEs) and the functional effect of variants within ESEs it is currently difficult to predict. We have previously developed a method of predicting which sequence changes within exons are likely to affect splicing, using BRCA1 as an example. In this paper, we have predicted ESEs in BRCA2 using the web-based tool ESEfinder and incorporated the same series of filters (increased threshold, 125 nt limit and evolutionary conservation of the motif) in order to identify predicted ESEs that are more likely to be functional. Initially 1114 ESEs were predicted for BRCA2 , however after all the filters were included, this figure was reduced to 31, 3% of the original number of predicted ESEs. Reported unclassified sequence variants in BRCA2 were found to colocalise to 55% (17/31) of these conserved ESEs, while polymorphisms colocalised to 0 of the conserved ESEs. In summary, we have identified a subset of unclassified sequence variants in BRCA2 that may adversely affect splicing and thereby contribute to BRCA2 disruption.

The protein tyrosine phosphatase receptor J, PTPRJ, is a tumor suppressor gene that has been implicated in a range of cancers, including breast cancer, yet little is known about its role in normal breast physiology or in mammary gland tumorigenesis. In this paper we show that PTPRJ mRNA is expressed in normal breast tissue and reduced in corresponding tumors. Meta-analysis revealed that the gene encoding PTPRJ is frequently lost in breast tumors and that low expression of the transcript associated with poorer overall survival at 20 years. Immunohistochemistry of PTPRJ protein in normal human breast tissue revealed a distinctive apical localisation in the luminal cells of alveoli and ducts. Qualitative analysis of a cohort of invasive ductal carcinomas revealed retention of normal apical PTPRJ localization where tubule formation was maintained but that tumors mostly exhibited diffuse cytoplasmic staining, indicating that dysregulation of localisation associated with loss of tissue architecture in tumorigenesis. The murine ortholog, Ptprj, exhibited a similar localisation in normal mammary gland, and was differentially regulated throughout lactational development, and in an in vitro model of mammary epithelial differentiation. Furthermore, ectopic expression of human PTPRJ in HC11 murine mammary epithelial cells inhibited dome formation. These data indicate that PTPRJ may regulate differentiation of normal mammary epithelia and that dysregulation of protein localisation may be associated with tumorigenesis.