TY - JOUR
T1 - Role of proton-coupled folate transporter in pemetrexed resistance of mesothelioma
T2 - Clinical evidence and new pharmacological tools
AU - Giovannetti, E.
AU - Zucali, P. A.
AU - Assaraf, Y. G.
AU - Funel, N.
AU - Gemelli, M.
AU - Stark, M.
AU - Thunnissen, E.
AU - Hou, Z.
AU - Muller, I. B.
AU - Struys, E. A.
AU - Perrino, M.
AU - Jansen, G.
AU - Matherly, L. H.
AU - Peters, Godefridus J.
PY - 2017
Y1 - 2017
N2 - Background: Thymidylate synthase (TS) has a predictive role in pemetrexed treatment of mesothelioma; however, additional chemoresistance mechanisms are poorly understood. Here, we explored the role of the reduced-folate carrier (RFC/SLC19A1) and proton-coupled folate transporter (PCFT/SLC46A1) in antifolate resistance in mesothelioma. Patients and methods: PCFT, RFC and TS RNA and PCFT protein levels were determined by quantitative RT-PCR of frozen tissues and immunohistochemistry of tissue-microarrays, respectively, in two cohorts of pemetrexed-treated patients. Data were analyzed by t-test, Fisher's/log-rank test and Cox proportional models. The contribution of PCFT expression and PCFT-promoter methylation to pemetrexed activity were evaluated in mesothelioma cells and spheroids, through 5-aza-20-deoxycytidinemediated demethylation and siRNA-knockdown. Results: Pemetrexed-treated patients with low PCFT had significantly lower rates of disease control, and shorter overall survival (OS), in both the test (N=73, 11.3 versus 20.1 months, P=0.01) and validation (N=51, 12.6 versus 30.3 months, P=0.02) cohorts. Multivariate analysis confirmed PCFT-independent prognostic role. Low-PCFT protein levels were also associated with shorter OS. Patients with both low-PCFT and high-TS levels had the worst prognosis (OS, 5.5 months), whereas associations were neither found for RFC nor in pemetrexed-untreated patients. PCFT silencing reduced pemetrexed sensitivity, whereas 5-aza-20- deoxycytidine overcame resistance. Conclusions: These findings identify for the first time PCFT as a novel mesothelioma prognostic biomarker, prompting prospective trials for its validation. Moreover, preclinical data suggest that targeting PCFT-promoter methylation might eradicate pemetrexed-resistant cells characterized by low-PCFT expression.
AB - Background: Thymidylate synthase (TS) has a predictive role in pemetrexed treatment of mesothelioma; however, additional chemoresistance mechanisms are poorly understood. Here, we explored the role of the reduced-folate carrier (RFC/SLC19A1) and proton-coupled folate transporter (PCFT/SLC46A1) in antifolate resistance in mesothelioma. Patients and methods: PCFT, RFC and TS RNA and PCFT protein levels were determined by quantitative RT-PCR of frozen tissues and immunohistochemistry of tissue-microarrays, respectively, in two cohorts of pemetrexed-treated patients. Data were analyzed by t-test, Fisher's/log-rank test and Cox proportional models. The contribution of PCFT expression and PCFT-promoter methylation to pemetrexed activity were evaluated in mesothelioma cells and spheroids, through 5-aza-20-deoxycytidinemediated demethylation and siRNA-knockdown. Results: Pemetrexed-treated patients with low PCFT had significantly lower rates of disease control, and shorter overall survival (OS), in both the test (N=73, 11.3 versus 20.1 months, P=0.01) and validation (N=51, 12.6 versus 30.3 months, P=0.02) cohorts. Multivariate analysis confirmed PCFT-independent prognostic role. Low-PCFT protein levels were also associated with shorter OS. Patients with both low-PCFT and high-TS levels had the worst prognosis (OS, 5.5 months), whereas associations were neither found for RFC nor in pemetrexed-untreated patients. PCFT silencing reduced pemetrexed sensitivity, whereas 5-aza-20- deoxycytidine overcame resistance. Conclusions: These findings identify for the first time PCFT as a novel mesothelioma prognostic biomarker, prompting prospective trials for its validation. Moreover, preclinical data suggest that targeting PCFT-promoter methylation might eradicate pemetrexed-resistant cells characterized by low-PCFT expression.
KW - Expression
KW - Malignant pleural mesothelioma
KW - Methylation
KW - Outcome
KW - PCFT
KW - Pemetrexed
UR - http://www.scopus.com/inward/record.url?scp=85034110301&partnerID=8YFLogxK
U2 - https://doi.org/10.1093/annonc/mdx499
DO - https://doi.org/10.1093/annonc/mdx499
M3 - Article
C2 - 28945836
SN - 0923-7534
VL - 28
SP - 2725
EP - 2732
JO - Annals of Oncology
JF - Annals of Oncology
IS - 11
ER -