A method of diagnosing lung cancer in a subject-in-need thereof is provided. The method comprises: (a) providing a biological sample of the subject which comprises peripheral blood mononuclear cells (PBMCs); (b) in vitro contacting the PBMCs with a stimulant selected from the group consisting of the stimulants listed in Tables 3 and 4; and (c) measuring metabolic activity of the PBMCs having been contacted according to (b), wherein a statistically significant change in the metabolic activity of the PBMCs as compared to a control sample is indicative of lung cancer.