{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,2]],"date-time":"2026-10-02T20:50:54Z","timestamp":1790974254526,"version":"4.1.0"},"reference-count":24,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2023,4,15]],"date-time":"2023-04-15T00:00:00Z","timestamp":1681516800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Department of Clinical Medicine, Aarhus University"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJMS"],"abstract":"<jats:p>Follicular lymphoma (FL) is a lymphoid neoplasia characterized by an indolent clinical nature. Despite generally favorable prognoses, early progression and histological transformation (HT) to a more aggressive lymphoma histology remain the leading causes of death among FL patients. To provide a basis for possible novel treatment options, we set out to evaluate the expression levels of indoleamine 2,3-dioxygenase 1 (IDO1), an immunoinhibitory checkpoint molecule, in follicular and transformed follicular biopsies. The expression levels of IDO1 were assessed using immunohistochemical staining and digital image analysis in lymphoma biopsies from 33 FL patients without subsequent HT (non-transforming FL, nt-FL) and 20 patients with subsequent HT (subsequently transforming FL, st-FL) as well as in paired high-grade biopsies from the time of HT (transformed FL, tFL). Despite no statistical difference in IDO1 expression levels seen between the groups, all diagnostic and transformed lymphomas exhibited positive expression, indicating its possible role in novel treatment regimens. In addition, IDO1 expression revealed a positive correlation with another immune checkpoint inhibitor, namely programmed death 1 (PD-1). In summary, we report IDO1 expression in all cases of FL and tFL, which provides the grounds for future investigations of anti-IDO1 therapy as a possible treatment for FL patients.<\/jats:p>","DOI":"10.3390\/ijms24087314","type":"journal-article","created":{"date-parts":[[2023,4,17]],"date-time":"2023-04-17T03:14:09Z","timestamp":1681701249000},"page":"7314","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["IDO1 Protein Is Expressed in Diagnostic Biopsies from Both Follicular and Transformed Follicular Patients"],"prefix":"10.3390","volume":"24","author":[{"given":"Marie Beck Hairing","family":"Enemark","sequence":"first","affiliation":[{"name":"Department of Hematology, Aarhus University Hospital, 8200 Aarhus, Denmark"},{"name":"Department of Clinical Medicine, Aarhus University, 8000 Aarhus, Denmark"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Emma Frasez","family":"S\u00f8rensen","sequence":"additional","affiliation":[{"name":"Department of Hematology, Aarhus University Hospital, 8200 Aarhus, Denmark"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0166-8558","authenticated-orcid":false,"given":"Trine Engelbrecht","family":"Hybel","sequence":"additional","affiliation":[{"name":"Department of Hematology, Aarhus University Hospital, 8200 Aarhus, Denmark"},{"name":"Department of Clinical Medicine, Aarhus University, 8000 Aarhus, Denmark"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0089-4273","authenticated-orcid":false,"given":"Maja Dam","family":"Andersen","sequence":"additional","affiliation":[{"name":"Department of Hematology, Aarhus University Hospital, 8200 Aarhus, Denmark"},{"name":"Department of Clinical Medicine, Aarhus University, 8000 Aarhus, Denmark"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Charlotte","family":"Madsen","sequence":"additional","affiliation":[{"name":"Department of Hematology, Aarhus University Hospital, 8200 Aarhus, Denmark"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kristina Lystlund","family":"Lauridsen","sequence":"additional","affiliation":[{"name":"Department of Pathology, Aarhus University Hospital, 8200 Aarhus, Denmark"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3459-7429","authenticated-orcid":false,"given":"Bent","family":"Honor\u00e9","sequence":"additional","affiliation":[{"name":"Department of Biomedicine, Aarhus University, 8000 Aarhus, Denmark"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Francesco","family":"d\u2019Amore","sequence":"additional","affiliation":[{"name":"Department of Hematology, Aarhus University Hospital, 8200 Aarhus, Denmark"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Trine Lindhardt","family":"Plesner","sequence":"additional","affiliation":[{"name":"Department of Pathology, Copenhagen University Hospital, 2100 Copenhagen, Denmark"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2158-3885","authenticated-orcid":false,"given":"Stephen Jacques","family":"Hamilton-Dutoit","sequence":"additional","affiliation":[{"name":"Department of Pathology, Aarhus University Hospital, 8200 Aarhus, Denmark"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5089-3271","authenticated-orcid":false,"given":"Maja","family":"Ludvigsen","sequence":"additional","affiliation":[{"name":"Department of Hematology, Aarhus University Hospital, 8200 Aarhus, Denmark"},{"name":"Department of Clinical Medicine, Aarhus University, 8000 Aarhus, Denmark"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2023,4,15]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"2375","DOI":"10.1182\/blood-2016-01-643569","article-title":"The 2016 revision of the World Health Organization classification of lymphoid neoplasms","volume":"127","author":"Swerdlow","year":"2016","journal-title":"Blood"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"83","DOI":"10.1038\/s41572-019-0132-x","article-title":"Follicular lymphoma","volume":"5","author":"Carbone","year":"2019","journal-title":"Nat. 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