Rescue of death receptor and mitochondrial apoptosis signaling in resistant human NSCLC in vivo

Abstract

Non small cell lung carcinoma (NSCLC) is a highly lethal malignancy that often becomes resistant to chemotherapy. To determine whether alterations in apoptotic signaling might contribute to such resistance, we established in vitro and in vivo models for sensitive and resistant human NSCLC. We found that resistance is due to multiple defects found in expression of CD95-L, CD95 and members of the Bcl-2 and IAP family, as well as caspase-8, -9 and -3 as examined by immunohistochemistry, Western blot analysis, gene array analysis and functional assays. Failure to activate death receptor, as well as mitochondrial apoptosis signaling, points to a central role of caspases. To restore apoptosis signaling we transfected NSCLC xenografts on nude mice with caspase-8 and -9. This treatment strongly induced apoptosis per se and sensitized the tumors to cisplatin-induced cell death. Thus, these findings indicate that re-expression of caspases might be an effective strategy to restore sensitivity for chemotherapy in NSCLC in vivo. © The most common cancer in the world today is lung cancer, with a mortality rate of more than 90%, and its incidence continues to rise worldwide. 1 Lung cancer is classified clinically into 2 major histologic types, small cell lung cancer (SCLC), which accounts for approximately 25% of cases, and non small cell lung cancer (NSCLC), which accounts for the remaining 75%, usually associated with poor prognosis. 2 NSCLC is normally sensitive to the first cycle of chemotherapy. However, in almost all patients chemotherapy-resistant NSCLC cells are selected, which resist further chemotherapy leading to rapid death of the respective patient. 3,4 Besides physiologic factors, such as pharmacokinetics, drug metabolism, drug delivery, drug location and tumor size, resistance has also been associated with decreased susceptibility to apoptosis. [5][6][7] Identifying the molecular determinants of apoptosis sensitivity and resistance to chemotherapy in NSCLC as well as in other solid tumor types may help improve its efficacy.Apoptosis is a physiologic mode of cell death that can be induced by adverse conditions, such as cellular stress, crosslinking of death receptors and exposure to anticancer agents. Apoptosis signaling converges in the activation of initiator caspases (procaspase-8, -9, -10), which leads to the proteolytic activation of downstream effector caspases (caspase-3, -6, -7) that cleave specific substrates. 8 -10 Two independent initiator pathways perform their action immediately upstream of these effector events: cross-linking of death receptors by their ligands and the release of apoptogenic factors from mitochondria. 10 -12 Chemotherapeutic agents and ␥-irradiation facilitate opening of the mitochondrial permeability transition pore and release of pro-apoptotic molecules such as cytochrome c. These molecules together with Apaf-1 and procaspase-9 form a holoenzyme complex termed "apoptosome." Caspase-9 in combination with this holoenzyme activates downstream caspases, which results in DNA fragmen...

Overexpression of Numb suppresses tumor cell growth and enhances sensitivity to cisplatin in epithelioid malignant pleural mesothelioma

“…These data indicate that Numb may be involved in conferring cisplatin sensitivity to MPM cells. Decreased caspase-3 and caspase-9 activation have been described as an additional mechanism of cisplatin resistance in various types of cancers (41)(42)(43)(44). To confirm whether or not Numb sensitizes MPM cells to cisplatin through the caspasedependent apoptotic pathway, further investigation is needed.…”

Overcoming chemoresistance of non-small cell lung carcinoma through restoration of an AIF-dependent apoptotic pathway

“…However, multiple results suggest that the classical caspase-dependent apoptotic pathways are not functional in NSCLC cells in response to cytotoxic agents in vitro (Yang et al, 2003;Bartling et al, 2004;Broker et al, 2004) and this may also be the case in vivo (Ferreira et al, 2001a, b). As an example, chemoresistant NSCLC exhibit a reduced expression of caspase-9 or caspase-3 (Okouoyo et al, 2004). We previously identified the U1810 cells as the most radioresistant among a panel of NSCLC cell lines (Joseph et al, 2001).…”

“…One therapeutic option that has been proposed to overcome resistance is the restoration of the defective caspase-dependent cell death pathway (Fennell, 2005). Overexpression of caspases in drug-resistant human NSCLC xenografts may overcome chemoresistance in vivo (Okouoyo et al, 2004). Pharmacological inhibition of IAP proteins restored NSCLC cells apoptosis sensitivity in vitro and in vivo, in mice grafted with human NSCLC (Yang et al, 2003).…”

MiR-155 inhibits the sensitivity of lung cancer cells to cisplatin via negative regulation of Apaf-1 expression

“…12 It has been reported that the mechanisms of cisplatin resistance involve increased repair or tolerance of DNA damage and changes, such as failed caspase-9 activation, in apoptotic signaling pathways. 13,14 Hence, novel strategies to monitor disease progression and to improve responses to cisplatin therapy are required.…”