Background and Objective: The high degree of malignancy of tumour cells is linked to alterations
of many physiological parameters like the intracellular pH (pHi). The pHi in cancer cell line is regulated
by the carbonic anhydrase IX (CA IX). The main enzymatic function of the CA IX protein is to
catalyze the hydration of carbon dioxide into bicarbonate ions and protons. CA IX expression in a broad
variety of human tumor tissues is associated with resistance to therapy. One promising approach is to
target the mechanism regulating pH homeostasis with carbonic anhydrase inhibitors like sulfamides and
Methods: In this work we have evaluated effects of umbelliferone and acetazolamide in a high resistant
melanoma cell line (A375) over expressing CA IX. Impact of effective doses of CA IX inhibitors on
apoptosis, intracellular pH (pHi), CA IX protein expression and functionality have been investigated.
Determination of effective doses of CA IX inhibitors was performed with MTT tests. We also evaluated
sensitization effect of CA inhibitors to conventional therapy as dacarbazin.
Results: We have used 10 µM Umbelliferone and 100 µM Acetazolamide as effective doses for 24h.
These doses did not induce any apoptosis. Umbelliferone induced a more important pHi decrease than
Acetalozamide from 7.3 to 7.08 and to 7.12 respectively, and a more important decrease in s-CA IX fraction
showing a decrease in CA IX function. We have demonstrated that pre-treatment with umbelliferone
or acetazolamide allows a better dacarbazin efficacy.
Conclusion: We have demonstrated that inhibitors modify intracellular pH and CAIX functionality and
sensitize cells to Dacarbazin. These original results complete the knowledge on Sulfamide CA IX inhibitors,
bring new insights about Coumarin compounds and offer new possibilities in high grade melanoma