LCK and small cell lung carcinoma: Although the Lck protein is known to be essential for both T-cell development and function (Veillette et al, 1989), this protein is aberrantly expressed in several malignancies, including colon carcinoma, small cell lung carcinoma, and prostate carcinoma with a trend of preferential expression in metastatic lesions (Robinson et al, 1996; McCracken et al, 1997; Krystal et al, 1998; Lutz et al, 1998).