Project description:Since bone metastatic breast cancer is an incurable disease, causing significant morbidity and mortality, understanding of the underlying molecular mechanisms would be highly valuable. Here, we describe in vitro and in vivo evidence for the importance of serine biosynthesis in the metastasis of breast cancer to bone. We first characterized the bone metastatic propensity of the MDA-MB-231(SA) cell line variant as compared to the parental MDA-MB-231 cells by radiographic and histological observations in the inoculated mice. Genome-wide gene expression profiling of this isogenic cell line pair revealed that all the three genes involved in the L-serine biosynthesis pathway, phosphoglycerate dehydrogenase (PHGDH), phosphoserine aminotransferase 1 (PSAT1), and phosphoserine phosphatase (PSPH) were upregulated in the highly metastatic variant. This pathway is the primary endogenous source for L-serine in mammalian tissues. Consistently, we observed that the proliferation of MDA-MB-231(SA) cells in serine-free conditions was dependent on PSAT1 expression. In addition, we observed that L-serine is essential for the formation of bone resorbing human osteoclasts and may thus contribute to the vicious cycle of osteolytic bone metastasis. High expression of PHGDH and PSAT1 in primary breast cancer was significantly associated with decreased relapse-free and overall survival of patients and malignant phenotypic features of breast cancer. In conclusion, high expression of serine biosynthesis genes in metastatic breast cancer cells and the stimulating effect of L-serine on osteoclastogenesis and cancer cell proliferation indicate a functionally critical role for serine biosynthesis in bone metastatic breast cancer and thereby an opportunity for targeted therapeutic interventions. Parental MDA-MB-231 cells and MDA-MB-231(SA) cells were cultured in cell culture flasks. RNA was isolated in order to compare the gene expression profiles of these cell variants. Total of two samples. No replicates.

Project description:Somatic ribosomal protein defects have recently been described in cancer, yet their impact on cellular transcription and translation remain poorly understood. Here we integrated mRNA sequencing, ribosome footprinting, polysomal RNA seq and quantitative mass spectrometry datasets obtained from an isogenic mouse lymphoid cell model in order to study the T-cell acute lymphoblastic leukemia (T-ALL) associated R98S mutation in ribosomal protein L10 (RPL10 R98S). RPL10 R98S induced changes in protein levels were to a much larger extent caused by transcriptional then translational changes and RPL10 R98S cells showed a gene signature corresponding to deregulation of hematopoietic transcription factors. Phosphoserine phosphatase (PSPH), a key enzyme in serine biosynthesis, displayed elevated transcription and translation and was one of the proteins showing the strongest upregulation in RPL10 R98S cells. Increased Psph protein levels were confirmed in RPL10 R98S engineered JURKAT cells and in hematopoietic cell cultures derived from Rpl10 R98S knock-in mice. Moreover, elevated serine and glycine biosynthesis in RPL10 R98S cells was supported by metabolic flux analyses. Analysis of PSPH expression levels in T-ALL patient samples revealed that PSPH upregulation is a generalized phenomenon in this disease, associated with elevated circulating serine and glycine levels. Addition of serine and glycine enhanced survival of stromal and myeloid cells, suggesting supportive effects on the hematopoietic niche. Finally, reduction of PSPH expression levels in T-ALL cell lines suppressed their in vitro proliferation and their capacity to expand in T-ALL xenograft models. In conclusion, transcriptome, translatome and proteome analysis of the RPL10 R98S mutation identified RPL10 R98S driven induction of cellular serine biosynthesis. Whereas serine metabolism has been implicated in cancer via PHGDH amplification, this is the first report supporting dependence of ALL cells on the serine biosynthesis enzyme PSPH.

Project description:D-3-Phosphoglycerate dehydrogenase (Phgdh; EC 1.1.1.95) is a necessary enzyme for de novo L-serine biosynthesis via the phosphorylated pathway. We demonstrated previously that Phgdh is expressed exclusively by neuroepithelium and radial glia in developing mouse brain and later mainly by astrocytes. Mutations in the human PHGDH gene cause serine deficiency disorders (SDD) associated with severe neurological symptoms such as congenital microcephaly, psychomotor retardation, and intractable seizures. We recently demonstrated that genetically engineered mice, in which the gene for Phgdh has been disrupted, have significantly decreased levels of serine and glycine, and exhibit malformation of brain such as microcephaly. The Phgdh null (KO) embryos exhibit lethal phenotype after gestational day 14, indicating that the phosphorylated pathway is essential for embryogenesis, especially for brain development. It is worth noting that the Phgdh knockout (KO) embryos primarily displayed microcephaly, which is the most conspicuous phenotype of patients with SDD. Thus, Phgdh KO mice are a useful animal model for studying the effect of diminished L-serine levels on development of the central nervous system and other organs. To better understand the mechanism underlying the molecular pathogenesis of SDD, we sought to examine whether gene expression is altered in the Phgdh KO mouse model. We identify genes that have altered expression in the head of the Phgdh KO embryos using the GeneChip array. Some of the genes identified by this method belong in functional categories that are relevant to the biochemical and morphological aberrations of the Phgdh deletion. Experiment Overall Design: Total RNA samples were prepared from head tissues from 2 embryos of Phgdh knockout and littermate wild-type controls. Experiment Overall Design: RNA of 4 biological replicates was hybridized to Affymetrix Mouse Genome 430 2.0 arrays. Five microgram total RNA was labelled according to the ENZO-protocol, fragmented and hybridized according to Affymetrix's protocols.

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Exogenous and Endogenous Sources of Serine Contribute to Colon Cancer Metabolism and Growth

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