STUDY QUESTION
Is it possible to purge leukemia cells from OT (OT) fragments before transplantation?
SUMMARY ANSWER
Our photodynamic therapy (PDT) approach has been shown to efficiently destroy leukemia cells from tumour-infiltration mimicking models (TIMs), indicating the feasibility of this technique to purge OT samples.
WHAT IS KNOWN ALREADY
Autotransplantation of cryopreserved OT is the most suitable option to preserve fertility for prepubertal girls and women who require immediate cancer treatment. Up to now, more than 200 live births have already been reported after OT cryopreservation and transplantation. Leukemia is the twelfth most common cancer in Europe among prepubertal girls and women of reproductive age and in 2020, the estimated number of new leukemia cases was higher than 33,000 in girls between 0 and 19 years old. Unfortunately, once their health has been restored, autotransplantation of cryopreserved OT for leukemia patients is not advised due to the high risk of transferring malignant cells back to the patient leading to leukemia recurrence.
STUDY DESIGN, SIZE AND DURATION
To safely transplant the OT from leukemia patients and restore their fertility, our goal was to develop a PDT strategy to eliminate leukemia ex vivo. To this end, we designed OR141-loaded niosomes (ORN) to create the most effective formulation for ex vivo purging OT fragments from acute myelogenous leukemia cells (n = 4). Moreover, to ensure that such treatments are not harmful to follicle survival and development so they can be deemed a potential fertility restoration alternative, the effect of the ORN-based PDT purging procedure on follicles was assessed after xenografting the photodynamic treated OT in SCID mice (n = 5). The work was carried out between September 2020 and April 2022 at the Catholic University of Louvain.
PARTICIPANTS/MATERIALS, SETTING AND METHODS
After establishing the best ORN formulation, our PDT approach was used to eradicate HL60 cells from ex vivo TIMs prepared by microinjection of cancer cell suspension in OT fragments. The purging efficiency was analyzed by droplet digital polymerase chain reaction and immunohistochemical analyses. Additionally, we evaluated the effect of ORN-based PDT on follicle density, survival and development and tissue quality in terms of fibrotic areas and vascularization after 7-day xenotransplantation to immunodeficient mice.
MAIN RESULTS AND THE ROLE OF CHANCE
The ex vivo purging of TIMs demonstrated that our PDT strategy could selectively eradicate the malignant cells from tissue fragments without affecting OT normal cells, as evidenced by PCR and immunohistochemical analysis. Regarding the effect of our PDT approach on follicle population and OT quality, our results after xenotransplantation revealed no significant difference between the follicle density of control (non-treated, grafted OT) and PDT-treated groups (2.38 ± 0.63 and 3.21 ± 1.94 morphologically normal follicles/mm2, respectively). In addition, our findings showed that the control and PDT-treated OT could be equally vascularized (7.65 ± 1.45% and 9.89 ± 2.21%, respectively). Similarly, the proportions of fibrotic area did not differ between the control (15.96 ± 5.94%) and PDT-treated groups (13.32 ± 3.05%).
LARGE SCALE DATA
N/A
LIMITATIONS, REASONS FOR CAUTION
This study did not use OT fragments from leukemia patients, but TIMs created after injection of HL60 cells in OT from healthy patients. Therefore, while the results are promising, whether our PDT approach will be equally successful in eliminating malignant cells from leukemia patients remains to be assessed.
WIDER IMPLICATIONS OF THE FINDINGS
Our results showed that the purging procedure causes no significant impairment effect on follicle development and tissue quality, suggesting that our novel PDT procedure could be a promising strategy to destroy leukemia cells in fragments of OT, allowing safe transplantation in cancer survivors.
STUDY FUNDING/COMPETING INTEREST(S)
This study was supported by grants from the Fonds National de la Recherche Scientifique de Belgique (FNRS-PDR Convention grant number T.0004.20 awarded to C.A.A.), Fondation Louvain (awarded to C.A.A.; a Ph.D. scholarship awarded to S.M., as part of a legacy from Mr. Frans Heyes, and a Ph.D. scholarship awarded to A.D. as part of a legacy from Mrs. Ilse Schirmer) and Foundation Against Cancer (grant 2018-042 awarded to A.C.). The authors declare no competing interests.
WHAT DOES THIS MEAN FOR PATIENTS?
Cancer treatment can damage ovarian function, potentially impairing patient fertility. In prepubertal girls and women who need cancer therapy immediately, it is possible to remove the ovarian tissue before the cancer treatment, cryopreserve it in cryobanks, and transplant it after cancer remission. However, this strategy cannot be offered to leukemia patients because of the high risk of reintroduction of cancer cells present in the cryopreserved ovarian tissue, which could potentially lead to leukemia recurrence. In order to safely transplant the ovarian tissue from these patients, these leukemia cells should be destroyed first. An alternative to selectively eradicate these cells without harming the follicle population could be photodynamic therapy. Based on this hypothesis, this study aimed to develop a novel photosensitizer to destroy leukemia cells in ovarian fragments. Our results showed that we could successfully purge these cells without harming follicle survival and development and ovarian tissue quality. This suggests that our novel procedure could be a promising strategy to destroy leukemia cells in ovary fragments, allowing their safe transplantation in cancer survivors.