In addition, we also found the GPRC5A is down-regulated in lung tissues of pneumonia (Fig. 7a, b), suggesting the GPRC5A deficiency might promote the enrichment of SPA+ABCG1+ subset in S/TB region and SPA+ABCG1+might serve as markers for the early diagnosis of lung cancer. The gene discussed is ABCG1; the disease is pneumonia.