Pion-Nucleon Sigma Term and Strangeness in Nucleon

It is shown that the meson exchange interaction between dynamical quarks generated by the chiral symmetry breaking is of crucial importance to explain the empirical value of the pion-nucleon σ-term. The large contribution of ss and gluon to a nucleon mass is predicted by using the QCD energy-momentum trace anomaly from the pion-nucleon σ-term.