Impact of metallothionein-knockdown on cisplatin resistance in malignant pleural mesothelioma

Abstract

Malignant pleural mesothelioma (MPM) is a rare, but aggressive tumor with dismal prognosis. Platinum-based chemotherapy is regularly used as part of multimodality therapy. The expression of metallothioneins (MT) has been identified as a reason for cisplatin resistance, which often leads to early therapy failure or relapse. Thus, knockdown of MT expression may improve response to cisplatin treatment. The MT gene- and protein expression of the MPM-cell lines MSTO-211H, NCI-H2052 and NCI-H2452 and the human fibroblast cell line MRC-5, as well as their sensitivity to cisplatin treatment have been evaluated. Knockdown of MT1A, 1B and 2A expression was induced by RNA interference. MT expression was measured using quantitative real-time PCR. An in vitro Assay based on enzyme activity was used to detect cell viability, necrosis and apoptosis before and after incubation with cisplatin. MT2A gene expression could be detected in all MPM cell lines, showing the highest expression in NCI-H2452 and NCI-H2052, whereas gene expression levels of MT1A and MT1B were low or absent. The immunohistochemically protein expression of MT-I/II reflect MT2A gene expression levels. Especially for MSTO-211H cell presenting low initial MT2A levels, a strong induction of MT2A expression could be observed during cisplatin treatment, indicating a cell line-specific and platin-dependent adaption mechanism. Additionally, a MT2A-dependent cellular evasion of apoptosis during cisplatin could be observed, leading to three different MT based phenotypes. MSTO-211H cells showed lower apoptosis rates at an increased expression level of MT2A after cisplatin treatment (from sixfold to fourfold). NCI-H2052 cells showed no changes in MT2A expression, while apoptosis rate is the highest (8–12-fold). NCI-H2452 cells showed neither changes in alteration rate of MT2A expression nor changes in apoptosis rates, indicating an MT2A-independent resistance mechanism. Knockdown of MT2A expression levels resulted in significantly induced apoptotic rates during cisplatin treatment with strongest induction of apoptosis in each of the MPM cell lines, but in different markedness. A therapeutic meaningful effect of MT2A knockdown and subsequent cisplatin treatment could be observed in MSTO-211H cells. The present study showed MT2A to be part of the underlying mechanism of cisplatin resistance in MPM. Especially in MSTO-211H cells we could demonstrate major effects by knockdown of MT2A expression, verifying our hypothesis of an MT driven resistance mechanism. We could prove the inhibition of MT2A as a powerful tool to boost response rates to cisplatin-based therapy in vitro. These data carry the potential to enhance the clinical outcome and management of MPM in the future.

Multifunctional Role of Astrocyte Elevated Gene-1 (AEG-1) in Cancer: Focus on Drug Resistance

“…CYP3A4 overexpression in lung and primary breast cancers has been documented to contribute to docetaxel resistance [ 67 , 68 ]. Cisplatin can be inactivated by the overexpression of metallothioneins (MTs), leading to cisplatin resistance in cancers [ 69 , 70 ].…”

The protease DDI2 regulates NRF1 activation in response to cadmium toxicity

“…MT gene and protein levels increase following the exposure of different metals in both mouse and humans. Recently, it has been suggested that MT promotes chemoresistance during metal-based cancer chemotherapies ( Borchert et al., 2020 ; Rodrigo et al., 2021 ). Cisplatin is a platinum-based compound, commonly used in chemotherapy treatments alone or in combination with other drugs.…”

High MT2A Expression Predicts Worse Prognosis in Patients with Urothelial Carcinoma

“…In transurethral or ureteroscopic biopsy, specimens immunostained with MT2A can identify high-risk patients who should receive aggressive surgery to prevent undertreatment. Moreover, recent studies have demonstrated that high MT2A expression is a predictive biomarker of cisplatin resistance in osteosarcoma and mesothelioma [29,30]. Therefore, aggressive or novel therapeutic protocols should be considered and investigated in patients with UC with high MT2A expression.…”