{'fraction_non_alphanumeric': 0.04446460980036298, 'fraction_numerical': 0.019056261343012703, 'mean_word_length': 5.502949852507375, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Novel reciprocal fusion genes involving HNRNPC and RARG in acute promyelocytic leukemia lacking RARA rearrangement

Acute promyelocytic leukemia (APL) is a unique subtype of acute leukemia characterized by retinoic acid receptor alpha gene (RARA) rearrangements (RARArearranged APL), of which PML-RARa is the typical one. As an altered retinoic acid receptor, PML-RARA owns the ability to transmit oncogenic signals within the cell. PMLRARA competitively controls the DNA sequences of retinoic acid-responsive element (RARE) sites and has a negative effect on transcription, inhibits the activation of physiological ligands, and leads to the arrest of promyelocytic differentiation. However, there are some rare patients lacking RARA rearrangement although they share the same morphology and immunocytochemistry features with RARA -rearranged APL. The classification of such leukemias remains in chaos and they have been also termed as acute promyelocytic-like leukemias (APLL). For years the underlying molecular aberrations of APLL remained unrevealed, but in recent years, RARG and RARB rearrangenments have been found in APLL. RARA, RARB and RARG belong to the nuclear receptor superfamily, and their sequences and functions are highly similar. In the present study we identified a couple of novel reciprocal fusion genes involving the heterogeneous nuclear ribonucleoprotein C (HNRNPC) gene and the retinoic acid receptor gamma (RARG) gene in APLL. To our knowledges, the reciprocal fusions were identified in human disease for the first time. A 43-year-old man was referred to our hospital with fever and a sore throat. Laboratory investigations revealed the following patient characteristics: (1) hemoglobin level, 125 g/L; (2) platelet count, 57×10/L; and (3) white blood cell count 12×10L (1% blasts and 86% abnormal promyelocytes). No signs of coagulopathy were evident. Morphologic analysis of the bone marrow aspirate showed 86.5% microgranular atypical promyelocytes (Figure 1A). Analysis from flow cytometry showed that the blasts were positive for CD33, CD13, CD45, and cMPO and negative for CD14, CD34, CD16, CD56, HLA-DR, Bor T-cell markers. Thus, the patient started all-trans retinoic acid (ATRA, 60 mg/day) and arsenious acid (10 mg/day) treatment immediately. Afterwards, chromosomal analysis revealed the majority of metaphases were der(14)ins(14;?) (q24;?)t(14;17?) (q24;q11.2?),der17t(14;17?)(q24;q11.2?). Fluorescence in situ hybridization did not identify the PML/RARA rearrangement. A series of reverse transcription PCR (RTPCR) assays amplified the HOX11 gene and alternative transcripts of 31 fusion genes, including PML-RARA, NPM-RARA, PLZF-RARA, and BCR-ABL, which were all negative. Sanger sequencing detected no FLT3 mutation. A combined chemotherapy (daunorubicin plus cytarabine) was administrated immediately following ATRA, then, because RARA rearrangment was lacking, arsenious acid (days 1-7) was suspended. After three weeks of ATRA therapy no response was observed in blood cell counts, and no evidence suggested differentiation syndrome. A second bone marrow biopsy (Figure 1B) was subsequently peformed and the blasts were almost unchanged (87.5%) which resulted in the withdrawal of ATRA. Next, the patient received a new course of induction chemotherapy alone (homoharringtonine, daunorubicin and cytarabine, HDA) and he achieved a complete response (CR) this time. Afterwards, he received five cycles of chemotherapy, of which three were consolidated therapies (HAD, HA, and mitoxantrone plus cytarabine) and two were cytarabine intensive treatments. Unfortunately, the leukemia relapsed 1 year later, and two cycles of re-induction chemotherapy, MAC (mitoxantrone, cytarabine and cyclophosphamide) followed by FLAG regiment, were sequentially administrated. Yet the blast counts in the bone marrow remained almost at the same level as at the disease onset (87.2%). Subsequently, ATRA in combination with arsenious acid therapy of sufficient dose and duration was resumed and continued for four weeks. However, all treatments failed to produce any effects. The patient eventually died from sepsis. To identify molecular alterations, transcriptome sequencing (RNA-seq) analysis was performed using peripheral blood mononuclear cells which were obtained in the patient’ relapse phase. Total RNA (4.6 μg) was used to synthesize cDNA libraries, and rRNA were removed