Functional Determinants of Metastatic Dormancy

描述（由申请人提供）：大多数癌症患者将死于从播散性肿瘤细胞（DTC）发展而来的转移，有时在治疗后数十年，这表明DTC以休眠、非增殖状态存活。我们的长期目标是确定调节DTC休眠的机制。我们假设（i）肿瘤细胞休眠（即生长停滞）可能发生在传播期间和/或之后，以响应由不适宜的组织微环境和/或治疗施加的应激信号，以及（ii）应激信号反过来激活了一个强大的生存程序，有利于在休眠期间延长生存。使用实验模型，HEp 3头颈部鳞状细胞癌细胞，我们的实验室已经确定了新的机制，调节休眠肿瘤细胞的生长停滞和生存能力。这些依赖于ERK 1/2（促有丝分裂）和p38 a/B（应激）通路之间的信号平衡以及特定的下游基因表达程序。我们发现，在适应从体内培养条件HEp 3癌细胞重编程，以获得一个休眠的表型，其特征是一个长期的G 0/G1停滞时，重新注入体内。我们发现（i）休眠HEp 3细胞的生长停滞是由于复杂转录因子（TF）网络的p38 a依赖性调节。在这个网络中，p53和BHLHB 3是由p38转录诱导的，它们有助于静止。G 0/G1期阻滞进一步通过TF FoxM 1和c-Jun的p38 a依赖性抑制来加强;后者拮抗p53。我们还发现（ii）TF ATF 6a通过控制mTOR活化的替代途径调节休眠的存活组分。实际上，ATF 6a上调小GTdR heb，这反过来诱导mTOR-S6 K活化、对雷帕霉素的抗性和休眠肿瘤细胞的体内存活。因此，我们已经确定了有助于休眠肿瘤细胞静止和存活的基因和机制。我们还发现，HEp 3 DTC，但在骨髓微环境中是无法恢复增殖，而生长增强的主要网站和肺。这种显著的差异似乎是一种休眠程序。其基础是，在从骨髓中回收并在培养物中扩增后，这些细胞在重新注射到动物中时不能形成肿瘤。相反，它们在恢复生长之前会经历一个休眠阶段。我们假设与上述机制相似的机制允许DTC抵抗治疗或微环境诱导的细胞死亡，并在休眠状态下存活，为患者的转移性复发提供了来源。显然，诱导和/或延长DTC的生长停滞对患者有益，但阻断其生存机制将使其在复发发展之前被根除。因为抗癌治疗的最终成功严格依赖于治愈或预防转移，所以迫切需要在该领域取得进展以改善转移前体的治疗根除。我们相信这些发现具有重要意义，因为关于DTC休眠的知识将对我们如何理解和治疗癌症产生重要影响。 公共卫生相关性：我们将探讨基因程序调节诱导休眠，延长生存期和化疗耐药性的休眠肿瘤细胞。我们还将研究这些机制在播散性肿瘤细胞中的激活。这些研究将为如何阻止转移发展提供深入了解。

DESCRIPTION (provided by applicant): Majority of cancer patients will die of metastases that develop from disseminated tumor cells (DTCs) sometimes decades after treatment, suggesting that DTCs survive in a dormant, non-proliferative state. Our long-term goal is to identify the mechanisms regulating dormancy of DTCs. We hypothesize that (i) tumor cell dormancy (i.e. growth arrest) may happen during and/or after dissemination in response to stress signals imposed by an inhospitable tissue microenvironment and/or by therapy and that (ii) stress signaling in turn activates a robust survival program that favors prolonged survival during the dormancy periods. Using an experimental model, HEp3 head and neck squamous carcinoma cells, our laboratory has identified novel mechanisms regulating the growth arrest and survival capacity of dormant tumor cells. These depend on the signaling balance between ERK1/2 (mitogenic) and p38a/b (stress) pathways and a specific downstream gene expression program. We showed that during adaptation from in vivo to culture conditions HEp3 carcinoma cells reprogram to acquire a dormant phenotype characterized by a prolonged G0/G1 arrest when re-injected in vivo. We discovered that (i) the growth arrest of dormant HEp3 cells is due to p38a-dependent regulation of a complex transcription factor (TF) network. In this network p53 and BHLHB3 are transcriptionally induced by p38 and they contribute to quiescence. The G0/G1 arrest is further enforced by p38a-dependent inhibition of the TFs FoxM1 and c-Jun; the latter antagonizes p53. We also found that (ii) the TF ATF6a regulates the survival component of dormancy by controlling an alternative pathway to mTOR activation Indeed, ATF6a upregulates the small GTPase Rheb, which in turn induces mTOR-S6K activation, resistance to Rapamycin and survival of dormant tumor cells in vivo. Thus, we have pinpointed genes and mechanisms contributing to both the quiescence and survival of dormant tumor cells. We also discovered that HEp3 DTCs but in the bone marrow microenvironment are unable to resume proliferation, while growth ensues in the primary site and lungs. This remarkable difference seems to be a program of dormancy. The basis for this is that upon recovery from the bone marrow and expansion in culture these cells are unable to form tumors when re-injected in animals. Instead they undergo a dormancy phase before resuming growth. We hypothesize that similar mechanisms to those described above allow DTCs to resist therapy- or microenvironment-induced cell death and to survive in a dormant state, providing a source of metastatic recurrences in patients. Clearly, inducing and or extending the growth arrest of DTCs would be beneficial for patients, but blocking their survival mechanisms would allow their eradication before recurrences can develop. Because eventual success of anti- cancer therapy depends strictly on curing or preventing metastases, progress in this field is urgently needed to improve the therapeutic eradication of metastatic precursors. We believe these findings are of significance, as knowledge on DTC dormancy will have an important impact on how we understand and treat cancer. PUBLIC HEALTH RELEVANCE: We will explore the gene programs regulating the induction of quiescence, the prolonged survival and chemotherapy resistance of dormant tumor cells. We will also study the activation of these mechanisms in disseminated tumor cells. These studies will provide insight into how to stop metastasis development.