Effectiveness of adjuvant carboplatin-based chemotherapy compared to cisplatin in non-small cell lung cancer.

BACKGROUND: Cisplatin and vinorelbine given intravenously is a well-established adjuvant chemotherapy regimen after surgery for early non-small cell lung cancer. However, few validated alternatives exist when cisplatin is not indicated or tolerated. Carboplatin is frequently used in this setting. We evaluated the 5-year overall survival, progression-free survival and toxicity in patients treated for stage IB to IIIB resected non-small cell lung cancer receiving adjuvant carboplatin-based chemotherapy compared to cisplatin in association with vinorelbine. METHODS: Single-center retrospective study of patients having received adjuvant chemotherapy between January 2004 and December 2013 at the oncology clinic at Institut Universitaire de Cardiologie et de Pneumologie de Québec (Canada). Three sub-groups, cisplatin/vinorelbine, carboplatin/vinorelbine and the substitution of cisplatin/vinorelbine for carboplatin/vinorelbine (cisplatin/vinorelbine/carboplatin/vinorelbine), were studied during treatment. RESULTS: One hundred twenty-seven patients were included in this study. The median PFS was not significantly different, with 50.4 months for cisplatin/vinorelbine, 57.3 months for cisplatin/vinorelbine/carboplatin/vinorelbine and not yet achieved for the carboplatin/vinorelbine group ( p = 0.80). Overall survival also did not differ significantly between the three groups. The 5-year overall survival rates were 66% in cisplatin/vinorelbine group, 55% in carboplatin/vinorelbine group and 70% in cisplatin/vinorelbine/carboplatin/vinorelbine group ( p = 0, 95). No differences were noted between groups concerning high-grade hematologic toxicity. CONCLUSIONS: Although the effectiveness and hematologic toxicity are comparable between cisplat in and carboplatin in the adjuvant treatment of resected non-small cell lung cancer, the results obtained corroborate the practice used at our oncology clinic. Nevertheless, more prospective studies would be needed to confirm these results.

Characterization of a novel interaction between the secretory Na+-K+-Cl- cotransporter and the chaperone hsp90.

The first isoform of the Na(+)-K(+)-Cl(-) cotransporter (NKCC1) is of central importance for the control of cellular ion concentration and epithelium-mediated salt secretion. Several studies have established that a change in intracellular [Cl(-)] (Cl(-)(i)) represents a key signaling mechanism by which NKCC1-induced Cl(-) movement is autoregulated and by which Cl(-) entry and exit on opposite sides of polarized cells are coordinated. Although this signaling mechanism is coupled to a pathway that leads to post-translational modification of the carrier, no unifying model currently accounts for the ion dependence of NKCC1 regulation. In this paper, evidence is presented for the first time that hsp90 associates with the cytosolic C terminus of NKCC1, probably when the carrier is predominantly in its unfolded form during early biogenesis. Evidence is also presented that the Cl(-)(i)-dependent regulatory pathway can be activated by a thermal stress but that it is no longer operational if NKCC1-expressing cells are pretreated with geldanamycin, an antibiotic that inhibits hsp90, albeit nonspecifically. Taken together, our data indicate that binding of hsp90 to NKCC1 may be required for Na(+)-K(+)-Cl(-) cotransport to occur at the cell surface and that it could play an important role in ion-dependent signaling mechanisms, insofar as the maneuvers that were used to alter the expression or activity of the chaperone do not exert their main effect by inducing other cellular events such as the unfolded protein response. Further studies will be required to elucidate the functional relevance of this novel interaction.

Self-interacting domains in the C terminus of a cation-Cl- cotransporter described for the first time.

The first isoform of the Na+-K+-Cl- cotransporter (NKCC1), a widely distributed member of the cation-Cl- cotransporter superfamily, plays key roles in many physiological processes by regulating the ion and water content of animal cells and by sustaining electrolyte secretion across various epithelia. Indirect studies have led to the prediction that NKCC1 operates as a dimer assembled through binding domains that are distal to the amino portion of the carrier. In this study, evidence is presented that NKCC1 possesses self-interacting properties that result in the formation of a large complex between the proximal and the distal segment of the cytosolic C terminus. Elaborate mapping studies of these segments showed that the contact sites are dispersed along the entire C terminus, and they also led to the identification of a critical interacting residue that belongs to a putative forkhead-associated binding domain. In conjunction with previous findings, our results indicate that the uncovered interacting domains are probably a major determinant of the NKCC1 conformational landscape and assembly into a high order structure. A model is proposed in which the carrier could alternate between monomeric and homo-oligomeric units via chemical- or ligand-dependent changes in conformational dynamics.

Purinergic-induced signaling in C11-MDCK cells inhibits the secretory Na-K-Cl cotransporter.

Purinergic inhibition of Na-K-Cl cotransport has been noted in various renal epithelial cells derived from the collecting tubule, including Madin-Darby canine kidney (MDCK) cells. In recent studies, we have observed purinergic inhibition of Na-K-Cl cotransport in C11-MDCK subclones (alpha-intercalated-like cells). Interestingly, Na-K-Cl cotransport activity was also detected in C7-MDCK subclones (principal-like cells) but was not affected by ATP. In this investigation, we have transfected the human Na-K-Cl cotransporter (huNKCC1) in both C11 and C7 cells to determine whether these differences in NKCC regulation by ATP were due to cell-specific purinoceptor signaling pathways or to cell-specific isoforms/splice variants of the transporter. In both cell lines, we found that endogenous as well as huNKCC1-derived cotransport activity was restricted to the basolateral side. In addition, we were able to show that extracellular application of 100 microM ATP or 100 microM UTP abolished NKCC activity in both mock- and huNKCC1-transfected C11 cells but not in mock- and huNKCC1-transfected C7 cells; in C11 cells, intriguingly, this inhibition was not affected by inhibitors of RNA and protein synthesis and occurred even though expression levels of UTP-sensitive P2Y2-, P2Y4-, and P2Y6-purinoceptors were not different from those observed in C7 cells. These results suggest that C11 cells express an undetermined type of UTP-sensitive P2-purinoceptors or a unique P2Y-purinoceptor-triggered signaling cascade that leads to inhibition of NKCC1.

Common human UGT1A polymorphisms and the altered metabolism of irinotecan active metabolite 7-ethyl-10-hydroxycamptothecin (SN-38).

7-Ethyl-10-hydroxycamptothecin (SN-38) is the pharmacologically active metabolite of irinotecan, in addition to being responsible for severe toxicity. Glucuronidation is the main metabolic pathway of SN-38 and has been shown to protect against irinotecan-induced gastrointestinal toxicity. The purpose of this study was to determine whether common polymorphic UDP-glucuronosyltransferase (UGT) affects SN-38 glucuronidation. First, kinetic characterization of SN-38-glucuronide (SN-38-G) formation was assessed for all known human UGT1A and UGT2B overexpressed in human embryonic kidney 293 cells. To assess the relative activity of UGT isoenzymes for SN-38, rates of formation of SN-38-G were monitored by liquid chromatography/mass spectrometry analysis and normalized by level of UGT cellular expression. Determination of intrinsic clearances predicts that hepatic UGT1A1 and UGT1A9 and the extrahepatic UGT1A7 are major components in SN-38-G formation, whereas a minor role is suggested for UGT1A6, UGT1A8, and UGT1A10. In support of the involvement of UGT1A9, a strong coefficient of correlation was observed in the glucuronidation of SN-38 and a substrate, mainly glucuronidate, by UGT1A9 (flavopiridol) by human liver microsomes (coefficient of correlation, 0.905; p = 0.002). In vitro functional experiments revealed a negative impact of the UGT1A1 allelic variants. Residual activities of 49, 7, 8, and 11% were observed for UGT1A1*6 (G(71)R), UGT1A1*27 (P(229)Q), UGT1A1*35 (L(233)R), and UGT1A1*7 (Y(486)D), respectively. Common variants of UGT1A7, UGT1A7*3 (N(129)K;R(131)K;W(208)R), and UGT1A7*4 (W(208)R), displayed residual activities of 41 and 28% compared with the UGT1A7*1 allele. Taken together, these data provide the evidence that molecular determinants of irinotecan response may include the UGT1A polymorphisms studied herein and common genetic variants of the hepatic UGT1A9 isoenzyme yet to be described.