The invention is based on the finding that the human RPT4 protein/gene can function as a therapeutic target for solid tumour type cancers, especially solid tumours of the colon, and that reducing the abundance of RPT4 in tumour cells causes a significant increase in cancer cell death, and potently decreases the survival and proliferation of cancer cells in tumour growth assays (FIGS. 3 and 4). A further, but linked, aspect of the invention is based on the finding that inhibitors of RPT4 significantly decrease the viability of chemotherapeutic-resistant tumours, especially solid tumours, especially colorectal solid tumours (FIG. 5). A further, but linked, aspect is based on the finding that the efficacy of conventional chemotherapeutic therapy, for example 5-FU/oxaliplatin therapy, is significantly improved when combined with treatment with a RPT4 inhibitor (FIG. 6). A further, but linked, aspect of the invention is based on the finding that levels of RPT4 in solid tumours such as colorectal cancer can function as a prognostic variable of outcome/survival (FIG. 2).
