This paper aims to contribute to the demonstration of the microwave dielectric spectroscopy relevance for biological applications. We demonstrate indeed that microwave dielectric spectroscopy may significantly identify the membrane permeabilization (and its consequence on cells) of cells induced by chemo-treatment. Standard deviations on both real and imaginary parts (resp.) of the permittivity between several experiments are below 0.08 and 0.06 (resp.), whereas the contrasts on these two parameters reach 1.92 and 1.30 (resp.) at 10 GHz. The contrasts to the standard deviation ratio are then above 22, which permits to convince the biologists that the technique can significantly and efficiently detect the viability state of a cells population in their traditional culture medium. Moreover, these results permits to predict that such a technique can evaluate the viability of a cells population with few percents of accuracy.