Non-orthogonal multiple access (NOMA) is widely viewed as a potential candidate for providing enhanced multiple access in future mobile networks by eliminating the orthogonal distribution of radio resources amongst the users. Nevertheless, the performance of NOMA can be significantly improved by combining it with other sophisticated technologies such as wireless data caching and device-to-device (D2D) communications. In this letter, we propose a novel cellular system model which integrates uplink NOMA with cache based device-to-device (D2D) communications. The proposed system would enable a cellular user to upload data file to base station while simultaneously exchanging useful cache content with another nearby user. We maximize the system sum rate by deriving closed form solutions for optimal power allocation. Simulation results demonstrate the superior performance of our proposed model over other potential combinations of uplink NOMA and D2D communications.