A mobile station apparatus configures first and second timers related to first and second groups. A first group of cells uses a first uplink transmission timing, and a second group of secondary cells uses a second uplink transmission timing. When the first timer of the first group has expired: all transmission HARQ buffers in association with the cells of the first group are flushed, the second timer is considered as expired, and an uplink transmission on any cells except random access preamble transmission on the primary cell is stopped. In a case where the second timer of the second group has expired: all transmission HARQ buffers in association with the secondary cells of the second group are flushed, and an uplink transmission on any cells in the second group except random access preamble transmission on the any cells in the second group is stopped.