ABSTRACT
A key cofactor of several enzymes implicated in DNA synthesis, repair, and methylation, folate has been shown to be required for normal cell growth and replication and is the basis for cancer chemotherapy using antifolates. γ-Glutamyl hydrolase (GGH) catalyzes the removal of γ-polyglutamate tails of folylpoly-/antifolylpoly-γ-glutamates to facilitate their export out of the cell, thereby maintaining metabolic homeostasis of folates or pharmacological efficacy of antifolates. However, the factors that control or modulate GGH function are not well understood. In this study, we show that intact GGH is not indispensable for the chemosensitivity and growth of acute lymphoblastic leukemia (ALL) cells, whereas GGH lacking N-terminal signal peptide (GGH-ΔN ) confers the significant drug resistance of ALL cells to the antifolates MTX and RTX. In addition, ALL cells harboring GGH-ΔN show high susceptibility to the change in folates, and glycosylation is not responsible for these phenotypes elicited by GGH-ΔN . Mechanistically, the loss of signal peptide enhances intracellular retention of GGH and its lysosomal disposition. Our findings clearly define the in vivo role of GGH in ALL cells and indicate a novel modulation of the GGH function, suggesting new avenues for ALL treatment in future.
Subject(s)
Drug Resistance, Neoplasm/genetics , Folic Acid Antagonists/pharmacology , Folic Acid/metabolism , Lymphocytes/drug effects , Protein Sorting Signals/genetics , gamma-Glutamyl Hydrolase/genetics , CRISPR-Cas Systems , Cell Line, Tumor , Cell Survival/drug effects , Gene Editing/methods , Glycosylation , HeLa Cells , Humans , Lymphocytes/metabolism , Lymphocytes/pathology , Lysosomes/drug effects , Lysosomes/metabolism , Methotrexate/pharmacology , Polyglutamic Acid/metabolism , Quinazolines/pharmacology , Thiophenes/pharmacology , gamma-Glutamyl Hydrolase/deficiencyABSTRACT
FUNDAMENTO Y OBJETIVO: La influencia de las alteraciones del metabolismo de la homocisteína en el pronóstico del síndrome coronario agudo sin elevación del segmento ST está sujeta a controversias. PACIENTES Y MÉTODO: Estudio prospectivo de 109 pacientes con síndrome coronario agudo sin elevación del segmento ST. Se determinaron los valores plasmáticos basales de homocisteína y folatos. Se analizaron sus características clínicas y se estudió la supervivencia según la presencia de concentración alta de homocisteína o baja de folatos en plasma. RESULTADOS: Tanto la supervivencia libre de episodios, como la supervivencia total a 2 años fue menor en los pacientes con folatos bajos (el 36,5 frente al 72,5%, p = 0,02, y el 48 frente al 94%, p < 0,001, respectivamente). Los pacientes con homocisteína elevada presentaron una menor supervivencia libre de episodios a los 2 años (el 57,4 frente al 89,1%, p < 0,01), y no se encontraron diferencias en términos de supervivencia total (el 86,3 frente al 97,3%, p = 0,11). En el análisis mediante regresión de Cox, la presencia de folatos bajos se identificó como predictor independiente de mortalidad (odds ratio [OR] = 8,33; intervalo de confianza [IC] del 95%, 1,88-33,33; p < 0,01); además, la hiperhomocisteinemia moderada fue un predictor independiente de episodios en el seguimiento (OR = 4,34; IC del 95%, 1,47-12,50; p < 0,01). CONCLUSIONES: En esta serie, los pacientes con hiperhomocisteinemia y/o valores bajos de folatos presentaron un pronóstico peor que el de aquéllos con valores normales. La presencia de valores bajos de folatos y la existencia de hiperhomocisteinemia moderada fueron predictores independientes de mal pronóstico en el seguimiento
BACKGROUND AND OBJECTIVE: The influence of homocysteine metabolism on the prognosis of acute coronary syndrome without ST elevation is controversial. PATIENTS AND METHOD: Prospective study of 109 patients admitted because of acute coronary syndrome without ST elevation. Basal plasmatic levels of homocysteine and folates were obtained. Clinical features and survival data on follow-up were registered. RESULTS: Both two years-free-of-events and total survival were lower in patients with low folate levels (36.5% vs 72.5%, p = 0.02; 48% vs 94%, p <.001). Patients with high homocysteine levels had lower two years-free-of-events survival (57.4% vs 89.1%, p <.01); but no difference in the total survival was observed (86.3% vs 97.3%, p = 0.11). The multivariate analysis showed that low folate levels was an independent predictor of mortality (odds ratio [OR] = 8.33; 95% confidence interval [CI], 1.88-33.33; p < 0.01), and moderate high homocysteine was an independent predictor of events on follow-up (OR = 4.34; 95% CI, 1.47-12.50; p < 0.01). CONCLUSIONS: Patients with high homocysteine or low folate levels have a poor prognosis compared with those with normal levels. On the other hand, low folate levels and moderate hyiperhomocysteinemia are independent predictors of bad prognosis in the follow-up
