SUMMARY Increased activation of the serine-glycine biosynthetic pathway is an integral part of cancer metabolism that drives macromolecule synthesis needed for cell proliferation. Whether this pathway is under epigenetic control is unknown. Here we show that the histone H3 lysine 9 (H3K9) methyltransferase G9A is required for maintaining the pathway enzyme genes in an active state marked by H3K9 monomethylation and for the transcriptional activation of this pathway in response to serine deprivation. G9A inactivation depletes serine and its downstream metabolites, triggering cell death with autophagy in cancer cell lines of different tissue origins. Higher G9A expression, which is observed in various cancers and is associated with greater mortality in cancer patients, increases serine production and enhances the proliferation and tumorigenicity of cancer cells. These findings identify a G9A-dependent epigenetic program in the control of cancer metabolism, providing a rationale for G9A inhibition as a therapeutic strategy for cancer.

Spontaneous apoptosis is decreased in the endometrial glands in women with endometriosis, especially during late secretory/menstrual and early proliferative phases of the cycle. This may indicate increased viability of endometrial cells shed during menses, facilitating their ectopic survival and implantation.

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The lymphotoxin-B receptor (LTBR) is a tumor necrosis factor receptor family member critical for the development and maintenance of various lymphoid microenvironments. Herein, we show that agonistic anti-LTBR monoclonal antibody (mAb) CBE11 inhibited tumor growth in xenograft models and potentiated tumor responses to chemotherapeutic agents. In a syngeneic colon carcinoma tumor model, treatment of the tumor-bearing mice with an agonistic antibody against murine LTBR caused increased lymphocyte infiltration and necrosis of the tumor. A pattern of differential gene expression predictive of cellular and xenograft response to LTBR activation was identified in a panel of colon carcinoma cell lines and when applied to a panel of clinical colorectal tumor samples indicated 35% likelihood a tumor response to CBE11. Consistent with this estimate, CBE11 decreased tumor size and/or improved long-term animal survival with two of six independent orthotopic xenografts prepared from surgical colorectal carcinoma samples. Targeting of LTBR with agonistic mAbs offers a novel approach to the treatment of colorectal and potentially other types of cancers.

SUMMARY The histone lysine demethylase KDM4C is often overexpressed in cancers primarily through gene amplification. The molecular mechanisms of KDM4C action in tumorigenesis are not well defined. Here we report that KDM4C transcriptionally activates amino acid biosynthesis and transport, leading to a significant increase in intracellular amino acid levels. Examination of the serine-glycine synthesis pathway reveals that KDM4C epigenetically activates the pathway genes under steady-state and serine deprivation conditions by removing the repressive histone modification H3 lysine 9 (H3K9) trimethylation. This action of KDM4C requires ATF4, a transcriptional master regulator of amino acid metabolism and stress responses. KDM4C activates ATF4 transcription and interacts with ATF4 to target serine pathway genes for transcriptional activation. We further present evidence for KDM4C in transcriptional coordination of amino acid metabolism and cell proliferation. These findings suggest a molecular mechanism linking KDM4C-mediated H3K9 demethylation and ATF4-mediated transactivation in reprogramming amino acid metabolism for cancer cell proliferation.

Differentiation status in neuroblastoma strongly affects clinical outcomes and inducing differentiation is a treatment strategy in this disease. However, the molecular mechanisms that control neuroblastoma differentiation are not well understood. Here we show that high-level HOXC9 expression is associated with neuroblastoma differentiation and is prognostic for better survival in neuroblastoma patients. HOXC9 induces growth arrest and neuronal differentiation in neuroblastoma cells by directly targeting both cell cycle-promoting and neuronal differentiation genes. HOXC9 expression is upregulated by retinoic acid (RA) and knockdown of HOXC9 expression confers resistance to RA-induced growth arrest and differentiation. Moreover, HOXC9 expression is epigenetically silenced in RA-resistant neuroblastoma cells and forced HOXC9 expression is sufficient to inhibit their proliferation and tumorigenecity. These findings identify HOXC9 as a key regulator of neuroblastoma differentiation and suggest a therapeutic strategy for RA-resistant neuroblastomas through epigenetic activation of HOXC9 expression.

Amplification of the oncogene MYCN is a tumorigenic event in the development of a subset of neuroblastomas that commonly consist of undifferentiated or poorly differentiated neuroblasts with unfavorable clinical outcome. The cellular origin of these neuroblasts is unknown. Additionally, the cellular functions and target cells of MYCN in neuroblastoma development remain undefined. Here we examine the cell types that drive neuroblastoma development in TH-MYCN transgenic mice, an animal model of the human disease. Neuroblastoma development in these mice begins with hyperplastic lesions in early postnatal sympathetic ganglia. We show that both hyperplasia and primary tumors are composed predominantly of highly proliferative Phox2B ؉ neuronal progenitors. MYCN induces the expansion of these progenitors by both promoting their proliferation and preventing their differentiation. We further identify a minor population of undifferentiated nestin

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