ENSG00000279284 and parathyroid gland adenoma: LOH and p27 deficiency was observed in a bronchial carcinoid and cervical neuroendocrine carcinoma from patients with MEN4, supporting that CDKN1B may act as a tumor suppressor gene; however, LOH was not observed in a parathyroid adenoma from one of these cases, and reduced expression of p27 was observed in a LOH-negative tumor, indicating that CDKN1B haploinsufficiency may lead to tumor development (13, 15).