Olaparib combined with chemotherapy for treatment of T-cell acute lymphoblastic leukemia relapse after unrelated umbilical cord blood transplantation

As one of the most common hematological malignancies, T-cell acute lymphoblastic leukemia (T-ALL) accounts for 20–25% of all acute lymphoblastic leukemia cases and is often accompanied by mediastinal space and central nervous system metastasis [1]. Currently, traditional combination chemotherapy is the main treatment approach for T-ALL. Although allogeneic hematopoietic stem cell transplantation (allo-HSCT) is suitable for patients with high-risk factors, recurrence after transplantation is still common, especially for patients with advanced disease [2]. Evidence suggests that specific genetic variants can predict disease prognosis, for instance, NOTCH1 and FBXW7 mutations are associated with a better outcome, while the SET-CAN fusion gene is associated with poor outcomes [3,4]. However, only a few targeted genes have been developed for T-ALL therapies. In the past few decades, the induction of DNA damage has been the main mechanism of tumor therapy, but it has insurmountable toxic side effects on normal cells. In recent years synthetic lethality strategies have received more attention on the rationale that tumor cells with homologous recombination DNA repair (HRR) defect are more sensitive to Poly ADP-ribose polymerase inhibitor (PARPi) [5]. To date, various PARPi have shown excellent efficacy in the treatment of breast and ovarian cancer with breast cancer 1/2 (BRCA 1/2) mutation [6]. However, the impact of PARPi on T-ALL with BRCA 1/2 mutation remains undefined [7]. Here, we report the use of PARPi olaparib combined with chemotherapy for the successful treatment of a T-ALL patient carrying a BRCA1 mutation who experienced a salvage treatment failure after the recurrence of umbilical cord blood transplantation (UCBT).

On 5 January 2018, a 24-year-old male patient was admitted to our hospital due to stomach discomfort for 1 month, fatigue for 2 weeks, and fever for 1 week. Complete blood count: WBC 0.59 × 10⁹/L, Hb 88 g/L, PLT 29 × 10⁹/L. Bone marrow aspiration showed lymphoblastic leukemia. Bone marrow flow cytometry showed that abnormal cells accounted for more than 50.6% of the nuclear cells which strongly express CD34, CD117, and CD7, express CD38, CD33, CD123, and CD99, but not CD13, CD11b, CD10, CD19, MPO, CD2, CDla, CD4, CD8, mCD3, CD16, and CD56, variable express TDT and cCD3, weakly express HLA-DR and CD5. This was consistent with the diagnosis of T-ALL.

Screening of 43 leukemia fusion genes detected SET-CAN but not 29 Ph-like ALL fusion genes. Cytogenetic analyses were normal, and no abnormalities of MLL and p53 were identified by fluorescence in situ hybridization. The patient received a VDCP regimen (Vindesine 2 mg/m², on day 1, 8, 15, 22, Cyclophosphamide 1 g/m² on day 1, Daunomycin 45 mg/m² on day 1–3, Prednisone 60 mg/m², on day 1–21) beginning on 15 January 2018. Bone marrow examination on the 15th day of chemotherapy indicated complete remission with residual abnormal T lymphoid blasts accounting for 1.49% of total nuclear cells (TNCs). The Hyper-CVAD B regimen (Methotrexate 1 g/m² on day 1, Cytarabine 2 g/m², q12h on day 2–3) was then administered as consolidation chemotherapy.

The patient returned to our hospital for unrelated umbilical cord blood transplantation (UCBT) in July 2018. The bone marrow aspiration before transplantation suggested remission with residual abnormal T lymphoid blasts accounting for 2.12% of TNCs and SET-CAN fusion gene positivity in 60.36% of the cells. Pretreatment with TBI/FLAG/CY was started on 26 July 2018, and cord blood infusion was administered with 1.19 × 10⁷/kg TNCs and 0.95 × 10⁵/kg CD34+ cells on 6 August 2018. Pre-engraftment syndrome (PES) occurred 7 days later and was improved by methylprednisolone treatment at a dose of 1 mg/kg. He reached donor chimerism of 100% on day +14, donor leukocyte engraftment on day +21, and platelet engraftment on day +70. On day +28, bone marrow morphology showed remission, the minimal residual disease (MRD) detected by flow cytometry was negative and no SET-CAN fusion gene was detected. On day +40, The patient developed diarrhea which was confirmed by colonoscopy and mucosal biopsy as GVHD and improved after received 2 mg/kg methylprednisolone and basiliximab treatment.

However, bone marrow aspiration on 26 August 2019, revealed 5% of lymphoblasts. Flow cytometry showed 2.52% abnormal T lymphoid blasts expressing for cCD3, CD34, CD38 and CD7 and negative for CD3, CD4, CD8, CD5, CD2, cTdT and CD56. The percentages of abnormal cells expressing HLA-ABC, HLA-DR/DP/DQ, PD-L1, CD86, and galectin-9 were 100%, 22.29%, 0.1%, 0.03%, and 52.54%, respectively, and SET-CAN fusion gene reached 70.7% indicating relapse of T-ALL. After administration of interferon (1MU subcutaneous injection qod), one cycle therapy with CD38 monoclonal antibody Daratumumab (16 mg/kg on day 1) [8], the Hyper-CVAD B regimen (Methotrexate 1 g/m² on day 1; Cytarabine 1.5 g/m² q12h on day 2–3), and CLAG regimen (G-CSF 5 μg/kg on day 0–4; Cladribine 5 mg/m² on day 1–5, and cytarabine 1 g/m² on day 1–5) sequentially, the patient did not achieve remission.

For exploring a feasibility treatment regimen, additional tests were done. HLA loss testing produced a positive result, and the testing for whole-exome sequencing of peripheral blood detected a BRCA1 missense mutation of c:3596C > T p.A1199V at exon10, a TREX1 gene missense mutation of c.318C > G p.N106K at exon2, and an MSH3 missense mutation of c:1858G > A p.D620N at exon13, which were further verified by sanger sequencing (Figure 1), suggesting that this patient might benefit from PARPi treatment. Olaparib-based combination therapy was proposed, and the patient provided oral and written consent after careful consultation. Beginning on 4 December 2019, the patient received the CLAG regimen as chemotherapy in combination with oral olaparib 300 mg twice a day for two weeks. The patient tolerated the olaparib combined with the CLAG regimen well. Grade IV bone marrow suppression occurred after chemotherapy and lasted for about three weeks. During this period, he developed fever and his blood culture showed Klebsiella pneumonia sepsis. After antibiotic treatment, the infection was well controlled. After this period, WBC resumed. On 7 January 2020, the bone marrow morphology showed remission, the platelets were not fully recovered, no abnormal cells were found in the detection of the bone marrow MRD, the SET-CAN fusion gene was quantitatively reduced to 0, and the donor Chimeric rate was 100%. On 19 February 2020, a second round of CLAG combined with olaparib was applied. Bone marrow examination on 20 March 2020, shows continued remission. The treatment regimen carried out according to the results of MRD and SET-CAN gene detection during the entire course of post-transplant is presented in Figure 2. Because of the lack of suitable donors for the second hematopoietic stem cell transplantation, the patient decided not to receive further combination therapy or a second allo-HSCT. Informed consent for publication of this case was obtained from the patient.

Figure 1. Sanger Sequence of Exon11 of BRCA1, Exon2 of TREX1, and Exon13 of MSH3, the Arrow Showing Mutations.

Figure 2. The entire course of treatment of post-transplant relapse.

As a sensor for DNA breaks, PARP recognizes and binds damaged DNA at single-strand DNA breaks [9]. After DNA is repaired, PARP1 release from DNA and resumes its catalytically inactive state. Recent studies have shown that certain PRRPi, including olaparib, can ‘trap’ PARP1 on DNA to prevent its release from the damaged sites. These stalled replication forks can be repaired and restarted via BRCA1 or BRCA2 dependent HRR, a form of DNA repair that uses a homologous DNA sequence to guide repair at the double-strand break. When cells become HRR defect caused by germline or somatic mutations of BRCA1 or BRCA2 genes, the impede replication forks stalled by PARPi cannot be repaired, which often leads to tumor cell death and synthetic lethality [5]. This synthetic lethal interaction between PARPi and BRCA1 or BRCA2 mutation was used for the treatment of breast, ovarian and other cancers, in which BRCA1 or BRCA2 are mutated [10]. It is recognized that deficiencies in some tumor suppressor genes involved in HRR, such as ATM, ATR, PALB2, and the FANC gene family were also shown to confer sensitivity to PARPi. Cancers with these mutations are therefore candidates for displaying BRCAness [11–13]. Therefore, BRCAness is a phenocopy of BRCA1 or BRCA2 mutation; it describes the situation in which an HRR defect exists in a tumor in the absence of a germline BRCA1 or BRCA2 mutation [11,14].

Although BRCA mutations in hematological tumors are uncommon, identification of the BRCAness phenotype may allow more leukemia patients to benefit from PARPi treatment [15]. LIM-domain only 2(LMO2) in diffuse large B cell lymphomas (DLBCL) and T-ALL cells are one type of the BRCAness reported by Salma Parvin et al. LMO2 is an important T-cell oncogene that overexpressed in T-ALL cells. They found that high expression of LMO2 in DLBCL and T-ALL cells results in HRR dysfunction that phenocopies BRCA1 and BRCA2 mutations, and exhibit high sensitivity to PARPi [16].

At present, in addition to detecting related gene mutations, HRR defects can also be screened by identifying ‘genomic scars’ caused by genome instability [17], including loss of heterozygosity (LOH), telomeric allelic imbalance (TAI), and large-scale state transitions (LST) [18–20]. One kind of LOH is HLA loss which often occurs under the donor immune pressure after HSCT [21], especially in relapsed patients after haploidentical stem cell transplantation and sometimes in unrelated transplantation and cord blood transplantation [22], its possible mechanism partly involves defects in the repair of double-stranded DNA breaks [23]. moreover, the patient’s two mutation genes, MSH3 and TREX1 were also shown to participate in various DNA mismatches repair [24,25]. Although there is no evidence to verify either HLA loss or MSH3 and TREX1 mutations are BRCAness or involved in HRR, they are all genomic instability events that might be a potential candidate for BRCAness.

Due to the presence of BRCA1 mutation and other gene abnormalities which might be ‘BRCAness’, we speculated that the mechanism of synthetic lethality contributed to the efficacy of olaparib in the present case.

In summary, this case suggests that T-ALL patients with BRCA 1/2 mutation or other ‘BRCAness’ phenotype may benefit from PARPi treatment. PARPi in combination with chemotherapy may be a new option for relapsed patients after allo-HSCT if salvage treatment is ineffective. Studies in larger cohorts are needed to validate the effectiveness of this treatment approach.

Acknowledgments

The authors would like to thank Medjaden Inc. for editing and proofreading the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The authors confirm that the data supporting the findings of this study are available within the article.