If the initial tissue level of RANKL is sufficient for the formation of a traveling wave-like front of osteoclasts in the absence of PTHrP production (Figure 7-A, ), switching on the PTHrP production leads to faster and bigger resorption fronts, and hence a further increase in tumor mass after 90 days (Figure 7-A, ). The gene discussed is PTHLH; the disease is neoplasm.