The reversal of multidrug resistance by an anti-CD19 ab.

描述(申请人提供)：多药耐药(MDR)是复发淋巴瘤的主要问题。能够逆转MDR和化学增敏的药物在有效剂量下往往是有毒的。因此，开发只作用于肿瘤细胞的无毒化学增敏剂是可取的。我们先前已经证明，抗CD19的单抗在体外可以通过干扰P-糖蛋白(Pgp)从细胞中排出药物的能力来逆转MDR B细胞淋巴瘤中P-糖蛋白(Pgp)介导的MDR。我们现在建议确定抗CD19如何逆转MDR，以及抗CD19是否能在体内使MDR淋巴瘤细胞对化疗增敏。如果是这样的话，我们将尝试通过将抗CD19与化疗和靶向免疫毒素(IT)相结合来进一步降低化疗水平，以治疗患有晚期MDR淋巴瘤的SCID小鼠。这一竞争性更新方案的具体目的是：1.继续阐明抗CD19在体外减少Pgp介导的MDR的机制。我们将检验两个假设：i)Pgp的功能受到损害，因为它在CD19交联化进入脂筏后被迫离开质膜的低密度脂微域(“脂筏”)，ii)抗CD19通过调节细胞内pH(Phi)而损害Pgp的功能，从而干扰细胞内的药物积累。2.确定这些单抗在化疗前或化疗期间给药是否能降低Pgp介导的多药耐药。3.探讨联合应用MDR逆转单抗和MDR旁路抗CD22单抗时化疗的最低剂量。综上所述，这些信息应该有助于我们确定如何优化人类多药耐药淋巴瘤的单抗治疗，以及开发与其他常规和实验性抗肿瘤药物联合使用的新方法。

DESCRIPTION (provided by applicant): Multidrug resistance (MDR) is a major problem in relapsed lymphomas. Agents which can reverse MDR and chemosensitize are often toxic at effective doses. It would therefore be desirable to develop non-toxic chemosensitizers which act only on tumor cells. We have previously shown that a monoclonal anti-CD19 antibody can reverse P-glycoprotein (Pgp)-mediated MDR in an MDR+ B cell lymphoma in vitro by interfering with the ability of Pgp to efflux drugs from the cells. We now propose to determine how anti-CD19 reverses MDR and whether anti-CD19 can chemosensitize MDR+ lymphoma cells in vivo. If so, we will attempt to lower chemotherapy even further by combining the anti-CD19 with chemotherapy and a targeted immunotoxins (IT) to treat SCID mice with advanced MDR+ lymphoma. The Specific Aims of this competitive renewal proposal are: 1. To continue to elucidate the mechanisms underlying the ability of anti-CD19 to decrease Pgp-mediated MDR in vitro. We will test two hypotheses: i) The function of Pgp is impaired because it is forced out of the low-density lipid microdomains ("lipid rafts") of the plasma membrane (where it is active) after CD19 is crosslinked and enters rafts, and ii) anti-CD19 impairs the function of Pgp by modulating of intracellular ph (pHi) and hence interfering with drug accumulation in cells. 2. To determine whether these MAbs can decrease Pgp-mediated MDR in vivo in SCID/lymphoma mice when administered before or during chemotherapy. 3. To determine the lowest doses of chemotherapy which can be given when both the MDR-reversing MAbs and the MDR-bypassing anti-CD22 IT are co-administered. Taken together, this information should help us determine how to optimize the MAb therapy of MDR+ lymphoma in humans as well as to develop novel ways to use MAbs in conjunction with other conventional and experimental anti-tumor agents.