Vitamin supplementation during chemotherapy has often been associated with lower recurrence and mortality rates in cancer patients. We had previously demonstrated that the multivitamin (C, D3, and B12)–cisplatin nanoparticle complex—NanoCisVital (NCV)—could alleviate chemotherapy-induced cancer fatigue. Chitosan is frequently used in functional nanomaterials to encapsulate drugs, because it is biodegradable, biocompatible, and non-toxic. The chitosan-based NCVs were prepared, and their physicochemical properties, size, and stability were evaluated before assessing their effect on cancer cell lines. The multivitamin mixture is packed in the core, and cisplatin is loaded at the periphery of the nanoparticle. This encapsulation facilitates the slow and sequential release of peripheral cisplatin and the core multivitamin combination. By increasing the amounts of vitamin and drug-encapsulated nanoparticles in breast and cervical cancer cell lines, the viable cell percentage was calculated. DDX3X promotes cancer cell proliferation, invasion, and metastasis, while Ki-67 promotes active cell proliferation in all cell types. DDX3X is elevated in several cancer types, and breast cancer cells express it abnormally. The Ki-67 protein is a biomarker of cell proliferation that is present throughout all active stages of the cell cycle but undetectable in the resting state. The expression of the DDX3X and Ki-67 genes is altered in NCV-treated cells. This study uses DDX3X and Ki-67 gene expression as a comparative measuring tool for the anti-cancer and cell proliferation effects of cisplatin and vitamins, respectively.