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Inactivation of adenomatous polyposis coli (APC) is common across many cancer types and serves as a critical initiating event in most sporadic colorectal cancers. APC deficiency activates WNT signaling, which remains an elusive target for cancer therapy, prompting us to apply the synthetic essentiality framework to identify druggable vulnerabilities for APC-deficient cancers. Tryptophan 2,3-dioxygenase 2 (TDO2) was identified as a synthetic essential effector of APC-deficient colorectal cancer. Mechanistically, APC deficiency results in the TCF4/β-catenin–mediated upregulation of TDO2 gene transcription. TDO2 in turn activates the Kyn–AhR pathway, which increases glycolysis to drive anabolic cancer cell growth and CXCL5 secretion to recruit macrophages into the tumor microenvironment. Therapeutically, APC-deficient colorectal cancer models were susceptible to TDO2 depletion or pharmacologic inhibition, which impaired cancer cell proliferation and enhanced antitumor immune profiles. Thus, APC deficiency activates a TCF4–TDO2–AhR–CXCL5 circuit that affects multiple cancer hallmarks via autonomous and nonautonomous mechanisms and illuminates a genotype-specific vulnerability in colorectal cancer. Significance: This study identifies critical effectors in the maintenance of APC-deficient colorectal cancer and demonstrates the relationship between APC/WNT pathway and kynurenine pathway signaling. It further determines the tumor-associated macrophage biology in APC-deficient colorectal cancer, informing genotype-specific therapeutic targets and the use of TDO2 inhibitors. This article is highlighted in the In This Issue feature, p. 1599

Supplementary Data from Synthetic Essentiality of Tryptophan 2,3-Dioxygenase 2 in APC-Mutated Colorectal Cancer

Supplementary Table from Synthetic Essentiality of Tryptophan 2,3-Dioxygenase 2 in APC-Mutated Colorectal Cancer

Inactivation of adenomatous polyposis coli (APC) is common across many cancer types and serves as a critical initiating event in most sporadic colorectal cancers. APC deficiency activates WNT signaling, which remains an elusive target for cancer therapy, prompting us to apply the synthetic essentiality framework to identify druggable vulnerabilities for APC-deficient cancers. Tryptophan 2,3-dioxygenase 2 (TDO2) was identified as a synthetic essential effector of APC-deficient colorectal cancer. Mechanistically, APC deficiency results in the TCF4/β-catenin–mediated upregulation of TDO2 gene transcription. TDO2 in turn activates the Kyn–AhR pathway, which increases glycolysis to drive anabolic cancer cell growth and CXCL5 secretion to recruit macrophages into the tumor microenvironment. Therapeutically, APC-deficient colorectal cancer models were susceptible to TDO2 depletion or pharmacologic inhibition, which impaired cancer cell proliferation and enhanced antitumor immune profiles. Thus, APC deficiency activates a TCF4–TDO2–AhR–CXCL5 circuit that affects multiple cancer hallmarks via autonomous and nonautonomous mechanisms and illuminates a genotype-specific vulnerability in colorectal cancer.Significance:This study identifies critical effectors in the maintenance of APC-deficient colorectal cancer and demonstrates the relationship between APC/WNT pathway and kynurenine pathway signaling. It further determines the tumor-associated macrophage biology in APC-deficient colorectal cancer, informing genotype-specific therapeutic targets and the use of TDO2 inhibitors.This article is highlighted in the In This Issue feature, p. 1599

Oncogenic KRAS (KRAS*) is a key tumor maintenance gene in pancreatic ductal adenocarcinoma (PDAC), motivating pharmacologic targeting of KRAS* and its effectors. Here, we explored mechanisms involving the tumor microenvironment (TME) as a potential basis for resistance to targeting KRAS*. Using the inducible KrasG12D;Trp53−/− PDAC mouse model, gain-of-function screens of epigenetic regulators identified HDAC5 as the top hit enabling KRAS* independent tumor growth. HDAC5-driven escaper tumors showed a prominent neutrophil-to-macrophage switch relative to KRAS*-driven tumors. Mechanistically, HDAC5 represses Socs3, a negative regulator of chemokine CCL2, resulting in increased CCL2, which recruits CCR2+ macrophages. Correspondingly, enforced Ccl2 promotes macrophage recruitment into the TME and enables tumor recurrence following KRAS* extinction. These tumor-associated macrophages in turn provide cancer cells with trophic support including TGFβ to enable KRAS* bypass in a SMAD4-dependent manner. Our work uncovers a KRAS* resistance mechanism involving immune cell remodeling of the PDAC TME.Significance:Although KRAS* is required for PDAC tumor maintenance, tumors can recur following KRAS* extinction. The capacity of PDAC cancer cells to alter the TME myeloid cell composition to support KRAS*-independent tumor growth illuminates novel therapeutic targets that may enhance the effectiveness of therapies targeting KRAS* and its pathway components.See related commentary by Carr and Fernandez-Zapico, p. 910.This article is highlighted in the In This Issue feature, p. 890

Epigenetic library information

Amyloid-induced neurodegeneration plays a central role in Alzheimer’s disease (AD) pathogenesis. Here, we show that telomerase reverse transcriptase (TERT) haploinsufficiency decreases BDNF and increases amyloid-β (Aβ) precursor in murine brain. Moreover, prior to disease onset, the TERT locus sustains accumulation of repressive epigenetic marks in murine and human AD neurons, implicating TERT repression in amyloid-induced neurodegeneration. To test the impact of sustained TERT expression on AD pathobiology, AD mouse models were engineered to maintain physiological levels of TERT in adult neurons, resulting in reduced Aβ accumulation, improved spine morphology, and preserved cognitive function. Mechanistically, integrated profiling revealed that TERT interacts with β-catenin and RNA polymerase II at gene promoters and upregulates gene networks governing synaptic signaling and learning processes. These TERT-directed transcriptional activities do not require its catalytic activity nor telomerase RNA. These findings provide genetic proof-of-concept for somatic TERT gene activation therapy in attenuating AD progression including cognitive decline.

Background Tumor-associated macrophages (TAMs) are key regulators of the complex interplay between cancer and the immune microenvironment. Tumor cell-derived spondin 2 (SPON2) is an extracellular matrix glycoprotein that has complicated roles in recruitment of macrophages and neutrophils during inflammation. Overexpression of SPON2 has been shown to promote tumor cell migration in colorectal cancer (CRC). However, the mechanism by which SPON2 regulates the accumulation of TAMs in the tumor microenvironment (TME) of CRC is unknown. Methods Immunohistochemistry was used to examine SPON2 expression in clinical CRC tissues. In vitro migration assays, transendothelial migration assays (iTEM), and cell adhesion assays were used to investigate the effects of SPON2 on monocyte/macrophage migration. Subcutaneous tumor formation and orthotopic implantation assays were performed in C57 BL/6 mice to confirm the effects of SPON2 on TAM infiltration in tumors. Results SPON2 expression is positively correlated with M2-TAM infiltration in clinical CRC tumors and poor prognosis of CRC patients. In addition, SPON2 promotes cytoskeletal remodeling and transendothelial migration of monocytes by activating integrin β1/PYK2 axis. SPON2 may indirectly induce M2-polarization through upregulating cytokines including IL10, CCL2 and CSF1 expression in tumor cells. Blocking M2 polarization and Macrophage depletion inhibited the SPON2-induced tumors growth and invasion. Furthermore, blocking the SPON2/integrin β1/PYK2 axis impairs the transendothelial migration of monocytes and cancer-promoting functions of TAMs in vivo. Conclusions Our findings demonstrate that SPON2-driven M2-TAM infiltration plays an important role during CRC tumor growth and metastasis. SPON2 may be a valuable biomarker guiding the use of macrophage-targeting strategies and a potential therapeutic target in advanced CRC.

Oncogenic KRAS (KRAS*) is a key tumor maintenance gene in pancreatic ductal adenocarcinoma (PDAC), motivating pharmacologic targeting of KRAS* and its effectors. Here, we explored mechanisms involving the tumor microenvironment (TME) as a potential basis for resistance to targeting KRAS*. Using the inducible KrasG12D;Trp53−/− PDAC mouse model, gain-of-function screens of epigenetic regulators identified HDAC5 as the top hit enabling KRAS* independent tumor growth. HDAC5-driven escaper tumors showed a prominent neutrophil-to-macrophage switch relative to KRAS*-driven tumors. Mechanistically, HDAC5 represses Socs3, a negative regulator of chemokine CCL2, resulting in increased CCL2, which recruits CCR2+ macrophages. Correspondingly, enforced Ccl2 promotes macrophage recruitment into the TME and enables tumor recurrence following KRAS* extinction. These tumor-associated macrophages in turn provide cancer cells with trophic support including TGFβ to enable KRAS* bypass in a SMAD4-dependent manner. Our work uncovers a KRAS* resistance mechanism involving immune cell remodeling of the PDAC TME. Significance: Although KRAS* is required for PDAC tumor maintenance, tumors can recur following KRAS* extinction. The capacity of PDAC cancer cells to alter the TME myeloid cell composition to support KRAS*-independent tumor growth illuminates novel therapeutic targets that may enhance the effectiveness of therapies targeting KRAS* and its pathway components. See related commentary by Carr and Fernandez-Zapico, p. 910. This article is highlighted in the In This Issue feature, p. 890

Gender exerts a profound impact on cancer incidence, spectrum and outcomes, yet the molecular genetic bases of such sex differences are ill-defined and presumptively ascribed to X-chromosome genes and sex hormones. Such sex differences are particularly prominent in colorectal cancer (CRC) where men experience higher metastases and mortality. A murine CRC model, engineered with an inducible transgene encoding oncogenic mutant KRASG12D and conditional null alleles of Apc and Trp53 tumor suppressors (designated iKAP), revealed higher metastases and worse outcomes specifically in males with oncogenic mutant KRAS (KRAS*) CRC. Integrated cross-species molecular and transcriptomic analyses identified Y-chromosome gene histone demethylase KDM5D as a transcriptionally up-regulated gene driven by KRAS*-mediated activation of the STAT4 transcription factor. KDM5D-dependent chromatin mark and transcriptome changes showed repression of regulators of epithelial cell tight junction and MHC class I complex components. Deletion of KDM5D in iKAP cancer cells increased tight junction integrity, decreased cell invasiveness, and enhanced cancer cell killing by CD8+ T cells. Conversely, iAP mice engineered with a Kdm5d transgene to provide constitutive KDM5D expression specifically in iAP cancer cells exhibited an increased propensity for more invasive tumors in vivo. Thus, KRAS*-STAT4-mediated upregulation of Y chromosome KDM5D contributes significantly to the sex differences in KRAS* CRC via its disruption of cancer cell adhesion properties and tumor immunity, thus providing an actionable therapeutic strategy for metastasis risk reduction for men afflicted with KRAS* CRC. Citation Format: Jiexi Li, Zhengdao Lan, Wenting Liao, Jielin Liu, Shan Jiang, Hong Seok Shim, Max Slotnik, Kyle A. LaBella, Wen-Hao Hsu, Xiaoying Shang, Denise Spring, Y Alan Wang, Ronald A. DePinho. Histone demethylase KDM5D drives sex-specific differences in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3515.

Loss of adenomatous polyposis coli (APC) is considered a critical initiating event in colorectal cancer (CRC), where it occurs in 90% of sporadic CRCs. APC deficiency results in activation of WNT; however, major hurdles persist to therapeutic intervention of this pathway. Here, the synthetic essentiality framework was used to discover other potential druggable vulnerabilities for APC-deficient cancers. Through this approach, tryptophan 2,3-dioxygenase 2 (TDO2) was identified as a synthetic essential effector of APC-deficient CRC. Upregulation of TDO2 activates the Kyn-AhR pathway, increasing glycolysis. Subsequent cancer cell growth and CXCL5 secretion leads to macrophage recruitment into the tumor microenvironment. APC-deficient CRC models were found to be susceptible to both TDO2 depletion and pharmacologic inhibition. Overall, this study identifies the TCF4-TDO2-AhR-CXCL5 axis as a critical pathway in the maintenance of APC-deficient CRC, informing potential genotype-specific therapeutic targets and the use of TDO2 inhibitors to combat this disease. Citation Format: Rumi Lee, Jiexi Li, Jun Li, Chang-Jiun Wu, Shan Jiang, Wen-Hao Hsu, Deepavali Chakravarti, Peiwen Chen, Kyle A. LaBella, Jing Li, Denise J. Spring, Di Zhao, Y. Alan Wang, Ronald A. DePinho. Synthetic essentiality identifies TDO2 as a key target in APC-deficient CRC [abstract]. In: Proceedings of the AACR Special Conference on Colorectal Cancer; 2022 Oct 1-4; Portland, OR. Philadelphia (PA): AACR; Cancer Res 2022;82(23 Suppl_1):Abstract nr IA014.

Gender exerts a profound impact on cancer incidence, spectrum and outcomes, yet the molecular genetic bases of such sex differences are ill-defined and presumptively ascribed to X-chromosome genes and sex hormones. Such sex differences are particularly prominent in colorectal cancer (CRC) where men experience higher metastases and mortality. A murine CRC model, engineered with an inducible oncogenic Kras transgene (KRAS*) and conditional null alleles of Apc and Trp53 tumor suppressors (designated iKAP), revealed higher metastases and worse outcomes specifically in males with KRAS* CRC. Integrated cross-species molecular and transcriptomic analyses identified Y-chromosome gene histone demethylase KDM5D as a transcriptionally up-regulated gene driven by KRAS*-mediated activation of the STAT4 transcription factor. KDM5D-dependent chromatin mark and transcriptome changes showed repression of regulators of epithelial cell tight junction and MHC class I complex components. Deletion of KDM5D in iKAP cancer cells increased tight junction integrity, decreased cell invasiveness, and enhanced cancer cell killing by CD8+ T cells. Conversely, iAP mice engineered with a Kdm5d transgene to provide constitutive KDM5D expression specifically in iAP cancer cells exhibited an increased propensity for more invasive tumors in vivo. Thus, KRAS*-STAT4-mediated upregulation of Y chromosome KDM5D contributes significantly to the sex differences in KRAS* CRC via its disruption of cancer cell adhesion properties and tumor immunity, thus providing an actionable therapeutic strategy for metastasis risk reduction for men afflicted with KRAS* CRC. Citation Format: Jiexi Li, Zhengdao Lan, Wenting Liao, James W. Horner, Jielin Liu, Shan Jiang, Hong S. Shim, Max Slotnik, Kyle A. LaBella, Wen-Hao Hsu, Denise J. Spring, Y. Alan Wang, Ronald A. DePinho. Histone demethylase KDM5D drives sex-specific differences in colorectal cancer [abstract]. In: Proceedings of the AACR Special Conference on Colorectal Cancer; 2022 Oct 1-4; Portland, OR. Philadelphia (PA): AACR; Cancer Res 2022;82(23 Suppl_1):Abstract nr PR011.

Summary Loss of imprinting (LOI) results in severe developmental defects, but the mechanisms preventing LOI remain incompletely understood. Here, we dissect the functional components of the imprinting control region of the essential Dlk1-Dio3 locus (called IG-DMR) in pluripotent stem cells. We demonstrate that the IG-DMR consists of two antagonistic elements: a paternally methylated CpG island that prevents recruitment of TET dioxygenases and a maternally unmethylated non-canonical enhancer that ensures expression of the Gtl2 lncRNA by counteracting de novo DNA methyltransferases. Genetic or epigenetic editing of these elements leads to distinct LOI phenotypes with characteristic alternations of allele-specific gene expression, DNA methylation, and 3D chromatin topology. Although repression of the Gtl2 promoter results in dysregulated imprinting, the stability of LOI phenotypes depends on the IG-DMR, suggesting a functional hierarchy. These findings establish the IG-DMR as a bipartite control element that maintains imprinting by allele-specific restriction of the DNA (de)methylation machinery.

Prostate cancer is a leading cause of cancer-related mortality in men. The widespread use of androgen receptor (AR) inhibitors has generated an increased incidence of AR-negative prostate cancer, triggering the need for effective therapies for such patients. Here, analysis of public genome-wide CRISPR screens in human prostate cancer cell lines identified histone demethylase JMJD1C (KDM3C) as an AR-negative context-specific vulnerability. Secondary validation studies in multiple cell lines and organoids, including isogenic models, confirmed that small hairpin RNA (shRNA)-mediated depletion of JMJD1C potently inhibited growth specifically in AR-negative prostate cancer cells. To explore the cooperative interactions of AR and JMJD1C, we performed comparative transcriptomics of 1) isogenic AR-positive versus AR-negative prostate cancer cells, 2) AR-positive versus AR-negative prostate cancer tumors, and 3) isogenic JMJD1C-expressing versus JMJD1C-depleted AR-negative prostate cancer cells. Loss of AR or JMJD1C generates a modest tumor necrosis factor alpha (TNFα) signature, whereas combined loss of AR and JMJD1C strongly up-regulates the TNFα signature in human prostate cancer, suggesting TNFα signaling as a point of convergence for the combined actions of AR and JMJD1C. Correspondingly, AR-negative prostate cancer cells showed exquisite sensitivity to TNFα treatment and, conversely, TNFα pathway inhibition via inhibition of its downstream effector MAP4K4 partially reversed the growth defect of JMJD1C-depleted AR-negative prostate cancer cells. Given the deleterious systemic side effects of TNFα therapy in humans and the viability of JMJD1C-knockout mice, the identification of JMJD1C inhibition as a specific vulnerability in AR-negative prostate cancer may provide an alternative drug target for prostate cancer patients progressing on AR inhibitor therapy.

Colorectal cancer has served as a genetic and biological paradigm for the evolution of solid tumors, and these insights have illuminated early detection, risk stratification, prevention, and treatment principles. Employing the hallmarks of cancer framework, we provide a conceptual framework to understand how genetic alterations in colorectal cancer drive cancer cell biology properties and shape the heterotypic interactions across cells in the tumor microenvironment. This review details research advances pertaining to the genetics and biology of colorectal cancer, emerging concepts gleaned from immune and single-cell profiling, and critical advances and remaining knowledge gaps influencing the development of effective therapies for this cancer that remains a major public health burden.

The identity of dividing cells is challenged during mitosis, as transcription is halted and chromatin architecture drastically altered. How cell type-specific gene expression and genomic organization are faithfully reset upon G1 entry in daughter cells remains elusive. To address this issue, we characterized at a genome-wide scale the dynamic transcriptional and architectural resetting of mouse pluripotent stem cells (PSCs) upon mitotic exit. This revealed distinct patterns of transcriptional reactivation with rapid induction of stem cell genes and their enhancers, a more gradual recovery of metabolic and cell cycle genes, and a weak and transient activation of lineage-specific genes only during G1. Topological reorganization also occurred in an asynchronous manner and associated with the levels and kinetics of transcriptional reactivation. Chromatin interactions around active promoters and enhancers, and particularly super enhancers, reformed at a faster rate than CTCF/Cohesin-bound structural loops. Interestingly, regions with mitotic retention of the active histone mark H3K27ac and/or specific DNA binding factors showed faster transcriptional and architectural resetting, and chemical inhibition of H3K27 acetylation specifically during mitosis abrogated rapid reactivation of H3K27ac-bookmarked genes. Finally, we observed a contact between the promoter of an endoderm master regulator, Gata6, and a novel enhancer which was preestablished in PSCs and preserved during mitosis. Our study provides an integrative map of the topological and transcriptional changes that lead to the resetting of pluripotent stem cell identity during mitotic exit, and reveals distinct patterns and features that balance the dual requirements for self-renewal and differentiation.

SUMMARYDysregulation of imprinted gene loci also referred to as loss of imprinting (LOI) can result in severe developmental defects and other diseases, but the molecular mechanisms that ensure imprint stability remain incompletely understood. Here, we dissect the functional components of the imprinting control region of the essential Dlk1-Dio3 locus (called IG-DMR) and the mechanism by which they ensure imprinting maintenance. Using pluripotent stem cells carrying an allele-specific reporter system, we demonstrate that the IG-DMR consists of two antagonistic regulatory elements: a paternally methylated CpG-island that prevents the activity of Tet dioxygenases and a maternally unmethylated regulatory element, which serves as a non-canonical enhancer and maintains expression of the maternal Gtl2 lncRNA by precluding de novo DNA methyltransferase function. Targeted genetic or epigenetic editing of these elements leads to LOI with either bi-paternal or bi-maternal expression patterns and respective allelic changes in DNA methylation and 3D chromatin topology of the entire Dlk1-Dio3 locus. Although the targeted repression of either IG-DMR or Gtl2 promoter is sufficient to cause LOI, the stability of LOI phenotype depends on the IG-DMR status, suggesting a functional hierarchy. These findings establish the IG-DMR as a novel type of bipartite control element and provide mechanistic insights into the control of Dlk1-Dio3 imprinting by allele-specific restriction of the DNA (de)methylation machinery.HIGHLIGHTSThe IG-DMR is a bipartite element with distinct allele-specific functionsA non-canonical enhancer within the IG-DMR prevents DNA methyltransferase activityTargeted epigenome editing allows induction of specific imprinting phenotypesCRISPRi reveals a functional hierarchy between DMRs that dictates imprint stability

Genetic inactivation of PTEN is common in prostate cancer and correlates with poorer prognosis. We previously identified CHD1 as an essential gene in PTEN-deficient cancer cells. Here, we sought definitive in vivo genetic evidence for, and mechanistic understanding of, the essential role of CHD1 in PTEN-deficient prostate cancer. In Pten and Pten/Smad4 genetically engineered mouse models, prostate-specific deletion of Chd1 resulted in markedly delayed tumor progression and prolonged survival. Chd1 deletion was associated with profound tumor microenvironment (TME) remodeling characterized by reduced myeloid-derived suppressor cells (MDSC) and increased CD8+ T cells. Further analysis identified IL6 as a key transcriptional target of CHD1, which plays a major role in recruitment of immunosuppressive MDSCs. Given the prominent role of MDSCs in suppressing responsiveness to immune checkpoint inhibitors (ICI), our genetic and tumor biological findings support combined testing of anti-IL6 and ICI therapies, specifically in PTEN-deficient prostate cancer. Significance: We demonstrate a critical role of CHD1 in MDSC recruitment and discover CHD1/IL6 as a major regulator of the immunosuppressive TME of PTEN-deficient prostate cancer. Pharmacologic inhibition of IL6 in combination with immune checkpoint blockade elicits robust antitumor responses in prostate cancer. This article is highlighted in the In This Issue feature, p. 1241

During self-renewal, cell-type-defining features are drastically perturbed in mitosis and must be faithfully reestablished upon G1 entry, a process that remains largely elusive. Here, we characterized at a genome-wide scale the dynamic transcriptional and architectural resetting of mouse pluripotent stem cells (PSCs) upon mitotic exit. We captured distinct waves of transcriptional reactivation with rapid induction of stem cell genes and transient activation of lineage-specific genes. Topological reorganization at different hierarchical levels also occurred in an asynchronous manner and showed partial coordination with transcriptional resetting. Globally, rapid transcriptional and architectural resetting associated with mitotic retention of H3K27 acetylation, supporting a bookmarking function. Indeed, mitotic depletion of H3K27ac impaired the early reactivation of bookmarked, stem-cell-associated genes. However, 3D chromatin reorganization remained largely unaffected, suggesting that these processes are driven by distinct forces upon mitotic exit. This study uncovers principles and mediators of PSC molecular resetting during self-renewal.

Oncogenic Kras (Kras*) plays a key role in tumor maintenance and therapeutic resistance in several cancer types, although the precise biologic functions and mechanisms are not completely understood. We had previously shown in pancreatic ductal adenocarcinoma that some tumors underwent spontaneous relapse and were devoid of Kras* expression and downstream canonical MAPK signaling, instead acquiring amplification and overexpression of the transcriptional coactivator Yap1. Functional studies established the role of Yap1 and the transcriptional factor Tead2 in driving Kras*-independent tumor maintenance. In a second previous study, we developed a faithful colorectal cancer (CRC) mouse model and showed that Kras* drove invasion and maintenance in CRC. Here, utilizing this CRC mouse model, we demonstrate that KRAS* promotes a pronounced immune-suppressive profile distinguished by a predominance of myeloid-derived suppressor cells (MDSCs). We performed integrated transcriptomic and genomic analyses that identified IRF2 (Interferon Regulatory Factor 2) as a key KRAS* effector mediating immune suppression. IRF2 suppresses MDSC migration and infiltration in KRAS*-expressing CRC tumors by targeting the CXCL3/CXCR2 axis. We also observed that de novo resistance of KRAS*-expressing tumors to anti-PD1 therapy could be overcome by enforced IRF2 expression or by treatment with SX-682, a small-molecule CXCR2 antagonist. In addition, CRC patient tumors with higher IRF2 expression showed increased response to anti-PD1 therapy. This KRAS*-mediated immune-suppressive mechanism provides a framework for CRC patient selection and combination therapies to enhance the effectiveness of immune checkpoint blockade therapy in advanced disease. Citation Format: Wen-Ting Liao, Michael J. Overman, Adam Boutin, Prasenjit Dey, Di Zhao, Guocan Wang, Jiexi Li, Zhengdao Lan, Jun Li, Xiaoying Shang, Ming Tang, Shan Jiang, Xingdi Ma, Peiwen Chen, Riham Katkhuda, Krittiya Korphaisarn, Deepavali Chakravarti, Qing Chang, Jianhua Zhang, Dipen M. Maru, Dean Y. Maeda, John A. Zebala, Scott Kopetz, Y. Alan Wang, Ronald A. DePinho. Context-dependent role of KRAS in GI malignancies [abstract]. In: Proceedings of the AACR Special Conference on Targeting RAS-Driven Cancers; 2018 Dec 9-12; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(5_Suppl):Abstract nr IA27.

During mitosis, transcription is halted and many chromatin features are lost, posing a challenge for the continuity of cell identity, particularly in fast cycling stem cells, which constantly balance self-renewal with differentiation. Here we show that, in pluripotent stem cells, certain histone marks and stem cell regulators remain associated with specific genomic regions of mitotic chromatin, a phenomenon known as mitotic bookmarking. Enhancers of stem cell-related genes are bookmarked by both H3K27ac and the master regulators OCT4, SOX2, and KLF4, while promoters of housekeeping genes retain high levels of mitotic H3K27ac in a cell-type invariant manner. Temporal degradation of OCT4 during mitotic exit compromises its ability both to maintain and induce pluripotency, suggesting that its regulatory function partly depends on its bookmarking activity. Together, our data document a widespread yet specific bookmarking by histone modifications and transcription factors promoting faithful and efficient propagation of stemness after cell division.

Male colorectal cancer (CRC) patients have higher rates of incidence, mortality and poorer responsiveness to therapy compared to female patients, making it critical to identify the significant factors contributing to the gender differences and to explore gender-specific therapeutic interventions. Here, combining unbiased expression profiling and xenograft mouse model discovered the Y chromosome gene KDM5D as a male-specific pro-metastasis gene and its upregulation contributes to poorer survival in both human and mouse. Knockout of Kdm5d in male metastatic CRC cell lines aborted the liver metastasis occurrence while overexpressing Kdm5d in female primary CRC cell lines enabled their metastasis potential. Mechanistically, ChIP-seq analysis showed KDM5D primarily works as a demethylase for histone modification H3K4me2/3, downregulating metastasis-suppressing genes. KDM5D also regulates the chromosome accessibility, indicated by H3K27Ac level change and validated with ATAC-seq. Kras G12D mutation regulates Kdm5d expression and is correlated with poorer survival in male mice, which is validated in silico in human CRC data in TCGA. KDM5 family inhibitor "compound 48" showed significant power to inhibit the migration capability of human metastatic CRC cell line LoVo. This study provided a new understanding of the effect of gender on CRC and a novel gender specific therapeutic target for metastatic CRC. Citation Format: Jiexi Li, Zhengdao Lan, Alan Y. Wang, Ron DePinho. KDM5D as a novel gender-specific gene target for metastatic colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-125.

Heterotypic interactions across diverse cell types can enable tumor progression and hold the potential to expand therapeutic interventions. Here, combined profiling and functional studies of glioma cells in glioblastoma multiforme (GBM) models establish that PTEN deficiency activates YAP1, which directly upregulates lysyl oxidase (LOX) expression. Mechanistically, secreted LOX functions as a potent macrophage chemoattractant via activation of the β1 integrin-PYK2 pathway in macrophages. These infiltrating macrophages secrete SPP1, which sustains glioma cell survival and stimulates angiogenesis. In PTEN-null GBM models, LOX inhibition markedly suppresses macrophage infiltration and tumor progression. Correspondingly, YAP1-LOX and β1 integrin-SPP1 signaling correlates positively with higher macrophage density and lower overall survival in GBM patients. This symbiotic glioma-macrophage interplay provides therapeutic targets specifically for PTEN-deficient GBM.

The biological functions and mechanisms of oncogenic KRASG12D (KRAS∗) in resistance to immune checkpoint blockade (ICB) therapy are not fully understood. We demonstrate that KRAS∗ represses the expression of interferon regulatory factor 2 (IRF2), which in turn directly represses CXCL3 expression. KRAS∗-mediated repression of IRF2 results in high expression of CXCL3, which binds to CXCR2 on myeloid-derived suppressor cells and promotes their migration to the tumor microenvironment. Anti-PD-1 resistance of KRAS∗-expressing tumors can be overcome by enforced IRF2 expression or by inhibition of CXCR2. Colorectal cancer (CRC) showing higher IRF2 expression exhibited increased responsiveness to anti-PD-1 therapy. The KRAS∗-IRF2-CXCL3-CXCR2 axis provides a framework for patient selection and combination therapies to enhance the effectiveness of ICB therapy in CRC.