  Mechanical signaling plays a key role in biological processes like embryo
development and cancer growth. One prominent way to probe mechanical properties
of tissues is to study their response to externally applied forces. Using a
particle-based model featuring random apoptosis and environment-dependent
division rates, we evidence a crossover from linear flow to a shear-thinning
regime with increasing shear rate. To rationalize this non-linear flow we
derive a theoretical mean-field scenario that accounts for the interplay of
mechanical and active noise in local stresses. These noises are respectively
generated by the elastic response of the cell matrix to cell rearrangements and
by the internal activity.
