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2016 ; 7
(39
): 63408-63423
Nephropedia Template TP
gab.com Text
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English Wikipedia
Altered pH gradient at the plasma membrane of osteosarcoma cells is a key
mechanism of drug resistance
#MMPMID27566564
Avnet S
; Lemma S
; Cortini M
; Pellegrini P
; Perut F
; Zini N
; Kusuzaki K
; Chano T
; Grisendi G
; Dominici M
; De Milito A
; Baldini N
Oncotarget
2016[Sep]; 7
(39
): 63408-63423
PMID27566564
show ga
Current therapy of osteosarcoma (OS), the most common primary bone malignancy, is
based on a combination of surgery and chemotherapy. Multidrug resistance mediated
by P-glycoprotein (P-gp) overexpression has been previously associated with
treatment failure and progression of OS, although other mechanisms may also play
a role. We considered the typical acidic extracellular pH (pHe) of sarcomas, and
found that doxorubicin (DXR) cytotoxicity is reduced in P-gp negative OS cells
cultured at pHe 6.5 compared to standard 7.4. Short-time (24-48 hours) exposure
to low pHe significantly increased the number and acidity of lysosomes, and the
combination of DXR with omeprazole, a proton pump inhibitor targeting lysosomal
acidity, significantly enhanced DXR cytotoxicity. In OS xenografts, the
combination treatment of DXR and omeprazole significantly reduced tumor volume
and body weight loss. The impaired toxicity of DXR at low pHe was not associated
with increased autophagy or lysosomal acidification, but rather, as shown by
SNARF staining, with a reversal of the pH gradient at the plasma membrane
(?pHcm), eventually leading to a reduced DXR intracellular accumulation. Finally,
the reversal of ?pHcm in OS cells promoted resistance not only to DXR, but also
to cisplatin and methotrexate, and, to a lesser extent, to vincristine.
Altogether, our findings show that, in OS cells, short-term acidosis induces
resistance to different chemotherapeutic drugs by a reversal of ?pHcm, suggesting
that buffer therapies or regimens including proton pump inhibitors in combination
to low concentrations of conventional anticancer agents may offer novel solutions
to overcome drug resistance.
|*Drug Resistance, Multiple
[MESH]
|*Drug Resistance, Neoplasm
[MESH]
|ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism
[MESH]