Colorectal tumors are hierarchically organized and governed by populations of self-renewing cancer stem cells, representing one of the deadliest types of cancers worldwide. Emergence of a cancer stem-like phenotype depends on epigenetic reprogramming, associated with profound transcriptional changes. As described for pluripotent reprogramming, epigenetic modifiers play a key role in developing and maintaining cancer stem cells by establishing embryonic stem-like transcriptional programs, thus altering the balance between self-renewal and differentiation. Through my work, I have identified overexpression of histone methyltransferase G9a as a risk factor for colorectal cancer, associated with shorter relapse-free survival. Moreover, using human transformed pluripotent cells as a surrogate model for cancer stem cells, I demonstrate that G9a activity is essential for the maintenance of an embryonic stem-like transcriptional signature that is required to promote self-renewal, tumorigenicity and an undifferentiated state. Such a role was also applicable to colorectal cancer, where inhibitors of G9a histone methyltransferase function induced intestinal differentiation while restricting tumor-initiating activity in patient-derived colorectal tumor samples. By integrating transcriptome profiling with G9a/H3K9me2 loci co-occupancy, the canonical Wnt pathway, epithelial-to-mesenchyme transition and extracellular matrix organization were identified as potential targets of such a chromatin regulation mechanism in colorectal cancer stem cells. Considering such novel insights on the role of G9a as a driver of the cancer stem cell phenotype, as well as a promoter of self-renewal, tumorigenicity and an undifferentiated state, I established and executed a multi-step drug screening pipeline to identify new repurposed drugs that selectively alter G9a functions in human CSCs. This pipeline revealed 3 new drug candidates that inhibit H3K9me2 deposition and impair human CSCs in culture. Future in-depth characterization of those candidates will represent an important step toward the development of novel CSC-targeting therapeutics.

Oral squamous cell carcinoma (OSCC), or oral cancer, accounts for the majority of head and neck cancers. Resistance to therapy is a challenge, and 5-year survival rate remains at ~50 percent. Lysine-specific demethylase 1 (LSD1) plays a crucial role in controlling cell homeostasis in health and disease. LSD1 is elevated in oral cancer and promotes metastasis and correlates with poor prognosis. LSD1 is a nuclear histone demethylase that has been implicated in maintaining the undifferentiated state of cancer-initiating stem cells and promoting OSCC. Large dataset analysis showed that genetic alterations, including upregulation of LSD1, are seen in clinical cancers including OSCC. This study aims to evaluate the unknown mechanism of LSD1 and determine if pharmacologic inhibition of LSD1 has preventative and/or therapeutic applications for OSCC. This study used the 4NQO mouse model to induce OSCC in mice and split the mice into 8 treatment groups. Each group received a different immunotherapy treatment (SP2509, Verteporfin, anti PD-1 and anti PD-L1 alone and in combination). Our results have shown that LSD1 inhibition reduces the development of gross pathologic lesions. LSD1 inhibition has also shown to cause differences in gene expression in preneoplasia and OSCC, attenuating many genes that are part of the pro-oncogenic gene network (LSD1, YAP, EGFR), immune checkpoints (PD-1 and PD-L1), and Hippo signaling effectors (YAP, TAZ). Interestingly, LSD1 has shown a role in regulating the immune microenvironment and promoting antitumor immunity, which led us to investigate LSD1 in combination with immune checkpoint antibodies (anti PD-1 and anti PD-L1). Our results show that LSD1 sensitizes to anti-PD-1 and anti-PD-L1 antibodies to treat mouse tongue OSCC. Thus, we showed for the first time that blocking LSD1 inhibits preneoplasia and OSCC feed-forward loop, which could have implications in OSCC prevention, chemo- and immunotherapeutic combinations.

Indiana University-Purdue University Indianapolis (IUPUI) / Setd1 histone 3 lysine 4 methyltransferases are critical for epigenetic regulation and gene expression. Setd1a is multiprotein complex comprised of several critical subunits including wdr82, which is essential for embryonic development, and cfp1, critical for regulation of both activation and repression of transcriptional programs required in basic and developmental cellular processes.

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Chronic obstructive pulmonary disease (COPD) is a major cause of morbidity and mortality worldwide and is a risk factor for lung cancer development. COPD encompasses both emphysema and chronic bronchitis, the pathogenesis of which are unclear. In this dissertation, I leveraged genome-wide gene-expression studies of emphysema and lung cancer to investigate pathogenesis and carcinogenesis in COPD. Tobacco smoke is the primary cause of emphysema. The most severe form is also associated with alpha1-antitrypsin deficiency (AATD) resulting from a mutation. In this study, I leveraged multiple lung samples from patients with emphysema, with or without AATD. While genes involved in tissue repair decreased with emphysema severity, the unfolded protein response (UPR) was uniquely changed in AATD lungs. AATD may play multiple roles in emphysema and UPR activation suggests AAT replacement therapy may be insufficient to treat this form of emphysema. Emphysema is a progressive disease, and the mean linear intercept (Lm) can serve as a surrogate of progression. I evaluated whether Lm increases in non-diseased lungs may represent similar processes to those occurring in emphysema, and could offer insight into early stages of disease or homeostasis. Genes involved in tissue repair increased with Lm in controls but decreased in disease. Tissue repair processes may be active in even the non-insulted lung, suggesting their activity is necessary for lung homeostasis and their deficiency may drive emphysema progression. Finally, COPD patients are at increased lung cancer risk, and transcriptomic changes common to both diseases could explain this risk. In both COPD and lung cancer, I discovered that H3K27Me3 regulated genes are repressed, and that the methyltransferase responsible for H3K27me3, EZH2, is induced. H3K27Me3, an oncogenic histone modification, may drive carcinogenesis and pathogenesis in COPD. Though usual and AATD emphysema share transcriptomic signatures associated with tissue repair, which may be active in the normal homeostatic lung, the UPR changes in AATD emphysema only; successful therapeutic strategies in emphysema will need to account for this difference. In COPD, H3K27Me3 may play a role in both pathogenesis and carcinogenesis, making it an attractive target for therapeutic interventions, but one that would need further augmentation in AATD. / 2019-11-01T00:00:00Z

京都大学 / 新制・課程博士 / 博士(医学) / 甲第24199号 / 医博第4893号 / 新制||医||1060(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 武藤 学, 教授 斎藤 通紀, 教授 浅野 雅秀 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

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