Surprisingly, the present inventors have discovered that expression of TAT-039 protein in human patients is associated with cancer, and that the overexpressed protein is present in plasma membrane fractions. Thus, the present inventors have discovered that TAT-039 is associated with abnormal development and growth, and may be useful as a target for the identification of anti-cancer compounds, including antibodies for use in immunotherapy. Accordingly, the present invention provides methods for the identification of compounds that inhibit TAT-039 expression or activity, comprising: contacting a candidate compound with a TAT-039 and detecting the presence or absence of binding between said compound and said TAT-039, or detecting a change in TAT-039 expression or activity. Methods are also included for the identification of compounds that modulate TAT-039 expression or activity, comprising: administering a compound to a cell or cell population, and detecting a change in TAT-039 expression or activity. The methods of the invention are useful for the identification of anti-cancer compounds.