Yes, you can. Any paper can be cited, whether it is preprinted, submitted or accepted but unpublished. Some journals do not encourage the citation of pre-printed papers, but the papers waiting for publication do not have this problem, because the papers have been reviewed and are as credible as published articles. Generally speaking, when citing such papers, you need to add "inpress" after the title of the reference. However, if your paper is based on an unpublished paper, it is best to attach it or include it in supporting materials.