α6 integrin subunit mediates laminin enhancement of cisplatin-induced apoptosis in testicular tumor germ cells

Abstract

Our study demonstrates that laminin potentiates cisplatin-induced apoptosis in NCCIT, a testicular tumor germ cell line. When cultured on laminin, NCCIT cells displayed a significantly higher susceptibility to cisplatin-induced apoptosis than on plastic or on other ECM components including fibronectin, Type IV collagen and vitronectin. This high cisplatin sensitivity observed on NCCIT cell cultured on laminin was mediated by the a6-integrin signaling. The knockdown of the a6-integrin subunit by small interfering RNAs suppressed the higher cisplatin-sensitivity supporting the existence of a crosstalk between laminin-a6-integrin signaling and cisplatin-induced apoptosis. Our findings indicate that in cisplatin-treated NCCIT cells, the laminin-a6-integrin signaling induces the activation of executioner procaspase-3 and -6 as well as apoptosis-inducing factor (AIF) transcription and expression. The ability of integrin-mediated specific stroma-tumor cell interactions to modulate the chemosensitive phenotype of a tumor cell might provide new insights to overcome cisplatin resistance of tumor cells. ' 2005 Wiley-Liss, Inc.Key words: apoptosis; cisplatin; laminin; testicular tumors; chemotherapy; integrin Resistance to anti-tumor drugs represents a major cause of cancer death. Platinum-based combination therapy is a standard chemotherapy in many cancers. Cisplatin, a major cytotoxic drug is used for treatment of a number of malignancies including ovarian, lung, head and neck, bladder and testicular cancer. Unfortunately, some tumors are intrinsically resistant or acquire resistance during the treatment.1 Testicular germ cell tumors (TGCT) are curable even in an advanced stage, by cisplatin-based chemotherapy, with an overall cure rate of approximately 80% 2,3 but in a few cases, however, a resistance occurs. The mechanism of this high sensitivity to cytotoxic drugs is not yet elucidated. It is now well established that cisplatin exerts its cytotoxic action through induction of apoptosis, at least in TGCT cells. [4][5][6] Cisplatin forms DNA intrastrand and interstrand cross-links that trigger cell cycle arrest and apoptosis in cancer cells. 7 The molecular mechanism underlying cisplatin resistance is multifactorial but increased DNA repair, tolerance to DNA adducts and inhibition of the apoptotic pathways are among the primary causes of tumor resistance. 8,9 Apoptosis is a tightly controlled multi-step mechanism of programmed cell death. Two well-characterized apoptotic pathways have been identified. The first one is mediated by death receptors such as Fas or tumor necrosis factor (TNF) receptor and a second one requires the release of apoptogenic factors from mitochondria. In both apoptotic pathways, the activation of initiator caspases (caspase-8 and -9) leads to the proteolytic activation of downstream effector caspases (caspase-3, -6 and -7) that cleave specific substrates such as nuclear lamins, cytoskeletal proteins and DNA ensuring irreversible cell death. 10 Recently the apoptosis-inducing factor (AIF), a mitoc...

Inhibition of mammary tumor growth by estrogens: is there a specific role for estrogen receptors alpha and beta?

“…The results observed in 32-2-HI tumors reproduced those observed in C4-HI tumors. * P \ 0.05, ** P \ 0.01 and *** P \ 0.001 transcription and expression [50], which agrees with our findings that integrin a6 expression was high in tumors with increased Aif expression ( Fig. 9 and Suppl.…”

“…9), suggesting that, in vivo, stromal components are playing an important role in apoptotic signaling. Thus, we evaluated the expression of the extracellular matrix protein laminin and one of its receptors, integrin a6, in C4-HI tumors because both have been implicated in potentiating apoptosis [50]. An increase in integrin a6 expression and of laminin distribution was observed in all treated tumors.…”

Apoptosis-Inducing Factor and Colon Cancer

“…In breast cancer cells, a number of chemotherapeutic agents induced apoptosis through depolarization of mitochondrial membrane with release of AIF [41][42][43][44]. Similar observations have been noted for other cancers such as myeloma [45], lymphoma [46], renal carcinoma [47], melanoma [29,30], pancreatic adenocarcinoma [48], lung cancer [49][50][51], glioma [52], prostate cancer [53,54], and testicular germ cell tumors [55].…”

Expression of galectin-3 in gonads and gonadal sex cord stromal and germ cell tumors

“…It has been suggested that RT-PCR alone is not a reliable method for the evaluation of galectin-3 expression, because macrophages and activated endothelial cells express galectin-3 (19). To confirm that galectin-3 mRNA is indeed present in tumor cells and is not due to the presence of macrophages in the stroma of germ cell tumors, we performed real-time PCR analysis on two pure human cell lines from a seminoma (JKT-1) (8) and a non-seminoma (NCCIT) (9). Both cell lines expressed galectin-3.…”

“…In addition, two pure human cell lines were analyzed. The JKT-1 cell line, a pure human seminoma cell line was kindly provided by P Fenichel (8) and the NCCIT cell line, a pure human non-seminomatous cell line (embryonal carcinoma) was kindly provided by E Tabone (9). Total RNA was extracted by using TRIzol Reagent according to the manufacturer's instructions (Life Technologies, France).…”