Pharmacological Blockage of XBP-1s Expression in Cancer

 描述（由申请人提供）：恶性细胞的高增殖率通常与蛋白质折叠、组装和转运速率的增加相关。严酷的肿瘤微环境也有助于内质网（ER）应激反应的过度激活，这是一种重要的生存机制。ER应激反应在成熟B细胞白血病或淋巴瘤中的功能作用在很大程度上被忽视，因为白血病和淋巴瘤细胞不像多发性骨髓瘤细胞那样扩增其ER。然而，我们的研究表明，慢性淋巴细胞白血病（CLL）确实需要激活ER应激反应途径才能生存。IRE-1/XBP-1通路代表了最保守的ER应激反应通路。IRE-1含有一个腔应力传感器结构域和一个胞质激酶/RNA酶结构域。RNase结构域对于IRE-1的功能至关重要，因为它从XBP-1 mRNA剪接26个核苷酸，导致翻译中的移码。剪接的XBP-1 mRNA编码一个功能性54-kDa XBP-1 s转录因子，该转录因子易位到细胞核并诱导分子伴侣和脂质的表达，以帮助蛋白质折叠和运输。虽然大多数转录因子仍然不可用，但XBP-1的特异性激活机制使IRE-1成为治疗干预的有吸引力的靶标。 我们最近开发了一种结构新颖的IRE-1抑制剂B-I 09，并证明了其在完整细胞中阻断XBP- 1表达和降低体内CLL肿瘤负荷的能力。IRE-1/XBP-1通路的遗传和药理学抑制会损害BCR信号传导，B-I 09与BTK抑制剂伊曲替尼协同作用，抑制原代小鼠和人B细胞癌细胞的生长。该项目旨在利用B-I 09和具有改善的药代动力学性质的选定前药类似物与BCR信号传导抑制剂组合用于治疗B细胞癌症。我们已经实施了一种综合方法，包括机械细胞生物学，体内疗效研究和化学优化，以开发CLL和其他B细胞恶性肿瘤的新治疗策略。在目标1中，我们提出在B细胞癌细胞系、原代小鼠CLL细胞、原代人样本和CLL体内Eµ-TLC 1小鼠模型中评价B-I 09与BCR信号通路抑制剂伊曲替尼（已批准，套细胞淋巴瘤，CLL）和福他替尼（II期，淋巴瘤）联合用药的作用机制和协同作用。在目标2中，我们将优化XBP-1 s表达抑制剂的药代动力学特性，并采用新的前药策略来提高这类新型抗癌药物的生物利用度，以进行先进的临床前研究。

 DESCRIPTION (provided by applicant): The high proliferation rate of malignant cells is often associated with an increase in the rates of protein folding, assembly, and transport. The harsh tumor microenvironment also contributes to hyperactivation of the endoplasmic reticulum (ER) stress response as an important survival mechanism. The functional role of the ER stress response in mature B-cell leukemia or lymphoma has been largely overlooked because leukemia and lymphoma cells do not expand their ER like that of multiple myeloma cells. However, our studies have shown that chronic lymphocytic leukemia (CLL) indeed requires activation of the ER stress response pathway for survival. The IRE-1/XBP-1 pathway represents the most conserved ER stress response pathway. IRE-1 contains a luminal stress-sensor domain, and a cytoplasmic kinase/RNase domain. The RNase domain is critical for the function of IRE-1, because it splices 26 nucleotides from the XBP-1 mRNA, causing a frame shift in translation. The spliced XBP-1 mRNA encodes a functional 54-kDa XBP-1s transcription factor, which translocates to the nucleus and induces the expression of chaperones and lipids to aid in protein folding and trafficking. While most transcription factors remain undruggable, the specific activation mechanism of XBP-1 renders IRE-1 an attractive target for therapeutic intervention. We recently developed a structurally novel IRE-1 inhibitor, B-I09, and demonstrated its ability to block XBP- 1 expression in intact cells and to reduce CLL tumor burden in vivo. Genetic and pharmacological inhibition of the IRE-1/XBP-1 pathway compromises BCR signaling, and B-I09 synergizes with the BTK inhibitor ibrutinib to inhibit the growth of primary mouse and human B-cell cancer cells. This project seeks to utilize B-I09 and selected prodrug analogs with improved pharmacokinetic properties in combination with inhibitors of BCR signaling for the treatment of B-cell cancer. We have implemented an integrated approach encompassing mechanistic cell biology, in vivo efficacy studies, and chemical optimization to develop novel treatment strategies for CLL and other B-cell malignancies. In Aim 1, we proposed to evaluate the mechanism of action and synergy of B-I09 in combination with the BCR signaling pathway inhibitors ibrutinib (approved, mantle cell lymphoma, CLL) and fostamatinib (phase II, lymphoma) in B-cell cancer cell lines, primary mouse CLL cells, primary human samples, and in an in vivo Eµ-TLC1 mouse model of CLL. In Aim 2, we will optimize the pharmacokinetic properties of inhibitors of XBP-1s expression and employ novel prodrug strategies to improve the bioavailability of this new class of anticancer agents for advanced preclinical studies.