Targeting the Microenvironment for Myeloma Growth Control

多发性骨髓瘤（MM）中溶骨性骨病的常见和典型诱导导致了这样一种观点，即骨病既是MM进展和转移的结果，也是MM进展和转移的必要条件。我们的报告和初步数据表明，破骨细胞通过产生某些丝氨酸蛋白酶（称为二肽基肽酶-IV活性和/或结构同源物（DASH）蛋白）来支持骨髓瘤细胞存活和转移，并且抑制破骨细胞或DASH蛋白酶的活性会抑制骨髓MM的生长。相反，我们发现，成骨细胞通过产生某些富含亮氨酸的小蛋白聚糖来减少骨髓瘤细胞的生长，（来自成骨细胞活化剂[甲状旁腺激素或抗DKKI]或细胞疗法[骨祖细胞]治疗）增加骨形成，产生不适宜的微环境，减弱体内MM进展。基于这些发现，我们假设现有局灶性病变中的微环境是骨髓瘤细胞长期存活和扩散的关键决定因素;因此，同时抑制破骨细胞活性和刺激骨形成对于维持患者对治疗的反应和预防转移至关重要。在具体目标1中，我们将确定骨合成代谢剂（例如，PTH，抗-DKKI），有或没有外源性成骨细胞前体，将维持由临床试剂（例如，美法仑、地塞米松、硼替佐米、来那度胺）和/或预防复发时的肿瘤转移。我们还将研究与这些效应相关的分子机制。在特定目标2中，我们将确定破骨细胞产生的DASH蛋白酶是否有助于MM诱导的骨病，支持MM在溶骨性病变中的存活，并通过小窝信号传导直接刺激转移，以及通过灭活中心趋化因子SDF-1减少骨髓瘤细胞的滞留间接刺激转移。在具体目标3中，我们将确定联合治疗以增加成骨细胞活性和抑制DASH蛋白酶活性在控制MM生长和播散以及预防复发方面是否具有比任一单独治疗方法更好的上级效果。通过与所有项目和核心的相互作用，使用我们的SCID-hu模型和与原代样品和骨髓瘤细胞系的共培养系统，我们将使用获得和损失方法，特异性抑制剂和重组蛋白来阐明与骨生长相关的因子的抗肿瘤和抗转移作用，以及MM中DASH蛋白酶的分子机制。

The common and typical induction of osteolytic bone disease in multiple myeloma (MM) led to the notion that bone disease is both a consequence and a necessity of MM progression and metastasis. Our reported and preliminary data suggest that osteoclasts support myeloma cell survival and metastasis through production of certain serine proteases known as dipeptidyl peptidase-IV activity and/or structure homolog (DASH) proteins and that inhibiting activity of osteoclasts or DASH proteases suppresses growth of medullary MM. Conversely, we found that osteoblasts reduce growth of myeloma cells through production of certain small leucine-rich proteoglycans and that increased osteoblast activity in myelomatous bones (from treating with osteoblast-activating agents [parathyroid hormone or anti-DKKI] or with cytotherapy [osteoprogenitor cells]) increases bone formation, creating an inhospitable microenvironment that attenuates MM progression in vivo. Based on these findings, we hypothesize that the microenvironment in existing focal lesions is a critical determinant of long-term survival and dissemination of myeloma cells; therefore, simultaneously inhibiting osteoclast activity and stimulating bone formation is critical for sustaining a patient's response to treatment and for preventing metastasis. In Specific Aim 1, we will determine whether increased bone formation by bone-anabolic agents (e.g., PTH, anti-DKKI), with or without exogenous osteoblast precursors, will sustain remission induced by clinical agents (e.g., melphalan, dexamethasone, bortezomib, lenalidomide), and/or prevent tumor metastasis upon relapse. We will also investigate molecular mechanisms associated with these effects. In Specific Aim 2, we will determine whether osteoclast-produced DASH proteases contribute to MM-induced bone disease, support survival of MM in osteolytic lesions, and stimulate metastasis directly by signaling through caveolae and indirectly through reduced retention of myeloma cells by inactivating the central chemokine SDF-1. In Specific Aim 3, we will determine whether combining treatments to increase activity of osteoblasts and inhibit activity of DASH proteases has superior effects on controlling MM growth and dissemination and on preventing relapse than either individual therapeutic approach. Through interactions with all projects and cores, using our SCID-hu model and coculture systems with primary samples and myeloma cell lines, we will unravel antitumor and antimetastatic effects of factors associated with bone anabolism, as well as molecular mechanisms of DASH proteases in MM using gain-and-loss approaches, specific inhibitors, and recombinant proteins.