Verma Amit, Wang Huamin, Manavathi Bramanandam, Fok Jansina Y, Mann Aman P, Kumar Rakesh, Mehta Kapil
Department of Experimental Therapeutics, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA.
Cancer Res. 2006 Nov 1;66(21):10525-33. doi: 10.1158/0008-5472.CAN-06-2387.
Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive neoplastic diseases and is virtually incurable. The molecular mechanisms that contribute to the intrinsic resistance of PDAC to various anticancer therapies are not well understood. Recently, we have observed that several drug-resistant and metastatic tumors and tumor cell lines expressed elevated levels of tissue transglutaminase (TG2). Because PDAC exhibits inherent resistance to various drugs, we determined the constitutive expression of TG2 in 75 PDAC and 12 PDAC cell lines. Our results showed that 42 of 75 (56%) PDAC tumor samples expressed higher basal levels of TG2 compared with the normal pancreatic ducts [odds ratio (OR), 2.439; P = 0.012]. The increased expression of TG2 in PDAC was strongly associated with nodal metastasis (OR, 3.400; P = 0.017) and lymphovascular invasion (OR, 3.055; P = 0.045). Increased expression of TG2 was also evident in all 12 cell lines examined. The elevated expression of TG2 in PDAC cell lines was associated with gemcitabine resistance and increased invasive potential. Overexpression of catalytically active or inactive (C(277)S mutant) TG2 induced focal adhesion kinase (FAK) activation and augmented invasive functions in the BxPC-3 cell line. Conversely, down-regulation of TG2 by small interfering RNA attenuated FAK phosphorylation. Immunoprecipitation and confocal microscopy data revealed that TG2 was associated with FAK protein in PDAC cells. The activated FAK colocalized with TG2 at focal adhesion points. These results show for the first time that elevated expression of TG2 can induce constitutive activation of FAK and thus may contribute to the development of drug resistance and invasive phenotypes in PDAC.
胰腺导管腺癌（PDAC）是最具侵袭性的肿瘤疾病之一，几乎无法治愈。导致PDAC对各种抗癌治疗产生内在抗性的分子机制尚未完全明确。最近，我们观察到几种耐药和转移性肿瘤及肿瘤细胞系中组织转谷氨酰胺酶（TG2）的表达水平升高。由于PDAC对各种药物具有固有抗性，我们测定了75例PDAC肿瘤组织和12种PDAC细胞系中TG2的组成性表达。我们的结果显示，75例（56%）PDAC肿瘤样本中，与正常胰腺导管相比，TG2的基础表达水平更高[比值比（OR），2.439；P = 0.012]。PDAC中TG2表达增加与淋巴结转移（OR，3.400；P = 0.017）和淋巴管浸润（OR，3.055；P = 0.045）密切相关。在所检测的所有12种细胞系中，TG2的表达也明显增加。PDAC细胞系中TG2表达升高与吉西他滨耐药性及侵袭潜能增加有关。催化活性或无活性（C(277)S突变体）TG2的过表达诱导了BxPC-3细胞系中粘着斑激酶（FAK）的激活并增强了侵袭功能。相反，小干扰RNA介导的TG2下调减弱了FAK磷酸化。免疫沉淀和共聚焦显微镜数据显示，PDAC细胞中TG2与FAK蛋白相关。活化的FAK与TG2在粘着斑处共定位。这些结果首次表明，TG2表达升高可诱导FAK的组成性激活，从而可能促进PDAC耐药性和侵袭性表型的发展。
