A first User Equipment (UE), a second UE, a first Radio Network Node (RNN), and methods therein for controlling interference between transmissions in a first system and transmissions in a second system. The first system comprises the first UE and the first RNN serving the first UE. The second system comprises the second UE and a second RNN serving the second UE. The first system has a first priority in a first part of a shared spectrum and the second system has a second priority in the first part of the shared spectrum, wherein the first priority is higher than the second priority. The method in the first UE comprises transmitting a signal to a second RNN that is to perform a downlink transmission to the second UE, which signal is configured to control the transmission of the second RNN.