Among all the subtypes of
breast cancer, triple-negative breast cancer (TNBC) has been associated with the worst prognosis. Recently, for many solid
tumors (including
breast cancer) metabolic reprogramming has appeared as a
cancer cell hallmark, and the elevated glycolytic pathway has been linked to their aggressive phenotype. In the present study, we evaluated the prognostic and therapeutic relevance of PFKFB3 (6-phosphofructo-2-
kinase/
fructose-2,6-bisphosphatase) in TNBCs. Prognostic significance of PFKFB3 expression was evaluated in overall breast
cancers as well as in TNBCs. PFKFB3 inhibitor (3PO potent analogue i.e.,
PFK15) cytotoxicity in TNBC cell lines (MDA-MB-231 and MDA-MB-468) was analyzed using an MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay.
Cancer cell physiological characteristics like clonogenicity and migration were also investigated after
PFK15 treatment. As fructose-2,6-bisphosphate (F-2,6-BP), has been associated with increased PFK-1 activity, the effect of PFKFB3 inhibition by
PFK15 was investigated on two major
isoforms of
phosphofructokinase-1 (PFK-1) in
breast cancer, that is,
phosphofructokinase-platelet type (PFKP) and
phosphofructokinase-liver type (PFKL) (relevant to
breast cancer). For PFKL inhibition, the
siRNA approach was used. PFKFB3 expression was significantly correlated with inferior overall survival in
breast cancer patients including TNBCs.
PFK15 treatment in TNBC cells (i.e., MDA-MB-231 and MDA-MB-468) resulted in a decreased PFKP expression, thereby leading to reduced colony formation ability, migration rate, and extracellular
lactate levels. However, to our surprise
PFK15 treatment in both TNBC cells also resulted in elevated PFKL levels. Our results demonstrated that the combinatorial inhibition of
PFK15 with siPFKL was more effective in TNBC cells, as it led to a decrease in colony formation ability, migration rate, extracellular
lactate levels, and PFK-1 activity when compared with individual treatments. Using bona fide PFKFB3 inhibitor, that is, AZ67, we further show that AZ67 treatment to TNBC cells has no effect either on the expression of PFKP and PFKL, or on the
lactate production. In summary, our present in vitro study demonstrated that 3PO derived
PFK15 mechanism of action is totally different from AZ67 in TNBC cells. However, we advocate that the PFK15-mediated inhibition (along with PFKL) on the TNBCs migration, colony formation, and PFK-1 activity can be further explored for the therapeutic advantage of TNBC patients.