Consistent with this observation that ERK is critical for signaling of airway smooth muscle cell activity in asthma, bronchoalveolar lavage fluid from asthma patients has been shown to augment ERK activation, increase cyclin D1 protein abundance, DNA synthesis, and proliferation of cultured human airway smooth muscle cells (Naureckas et al. 1999). The gene discussed is CCND1; the disease is asthma.