Dr Léa Lemaitre

Post Doc, Division of Gastroenterology and Hepatology, Stanford University, Stanford, CA, USA

invited by Christophe Grosset, team 6 MIRCADE, Methods and Innovations for the Research in Pediatric Cancers.

Title: Targeting Macrophage-Mediated Mechanisms of Immune Evasion as adjuvant therapy in TACE-resistant Hepatocellular Carcinoma.

Abstract:

A key obstacle to progress in treatment of hepatocellular carcinoma (HCC) is the notorious tenacity of HCC to recur. Transarterial chemoembolization (TACE) is the most common treatment for unresectable HCC, however, it fails to provide a durable cure. The crux of the problem lies in residual cancer cells that persist after TACE. Our goal is to understand how these residual cells escape immune detection and survive after TACE in order to develop effective adjuvant therapies.

We used both in vitro and in vivo methods to mimic TACE- resistance by generating doxorubicin resistant- residual HCC models. We performed single-cell RNA sequencing on 3D tumoroids (31,000 cells) of doxorubicin resistant vs control HCC in coculture with macrophages. In addition, HCC patient-derived tumor cells and macrophages were used for validation. We developed an immunocompetent mouse model of syngeneic orthotopic allograft model of HCC, using doxorubicin-resistant or control HCC cell lines to test adjuvant therapies.

Using scRNAseq of 3D tumoroid model, we show that doxorubicin-resistant cancer cells exhibit a stem-cell-like phenotype with high expression of stemness markers (CK19, CD44), TGFb pathway (TGFBR1) and cytokines driving pro- tumor macrophage polarization (CXCL8, CCL2). On the other hand, the macrophages co-cultured with doxorubicin-resistant HCC showed a pro-tumor phenotype with increased PDL1 expression. We validated this finding using patient-derived samples, showing that doxorubicin resistant HCC tumoroid co- culture increased PDL1 expression on macrophages. Further, mRNA FISH showed that the CD68+ macrophages expressed higher levels of TGFB1 in TACE-resistant HCC than primary HCC (p=0.0011). Based on our in vitro analysis we identified the TGFB pathway and PDL1 as potential synergistic targets for adjuvant therapy of TACE-resistant HCC. In our mouse model of doxorubicin-resistant orthotopic allografts, we showed that treatment with combined TgfbrI and anti-Pdl1 antibodies resulted in significantly reduced liver tumor burden (p=0.01). Flow cytometry analysis revealed immune remodeling with increased infiltration of CD8T cells and M1-like macrophage (CD86+/MHC- II+), along with depletion of macrophages (PDL1+/CD206+) in the liver of treated doxorubicin-resistant orthotopic allografts.

We generated in vitro 3D models of TACE-resistance in HCC and identified the mechanistic roles of the PDL1+ macrophage-derived TGFβ1 on stem-like cancer cell persistence. We developed a mouse model of doxorubicin-resistant HCC and demonstrated that combined targeting of Pdl1 and Tgfb1 blocks tumor progression and evokes and anti-tumor macrophage and CD8T cell immune response. Thus combined targeting of PDL1 and TGFB1 holds therapeutic potential as adjuvant therapy in TACE to eliminate residual HCC, reduce recurrence and improve patient outcomes in HCC.

Biosketch:

My long-term research goals are to improve immunotherapies for cancer treatment. My objective is to decipher the complexity of the immune system in the tumor microenvironment. My academic training as a pharmacist and research scientist provides me with a strong background in pharmacy, medicine, clinical research, immunology, and oncology.

In my first year of pharmacy residency, I was involved in clinical trials, and I developed a novel chromatographic method to detect errors in the administration of intravenous chemotherapy. During my residency, I developed a strong interest in oncology research leading me to pursue an integrated masters program under the mentorship of Dr. Bettina Couderc. I analyzed the crosstalk between macrophages and mesenchymal stromal cells (MSCs) in chemotherapy-resistant ovarian cancer leading to 3 co-author publications. This research project reinforced my passion for immune-oncology. To further understand the role of MSCs in cancer resistance to therapies, I pursued PhD training under the supervision of Dr. Bettina Couderc and Jill Corre, entitled “Phenotypic and functional characterization of cancer-associated MSCs in multiple myeloma”. This work advanced the understanding of the tumor microenvironment in multiple myeloma and led to the publication of two first-authored publications (1, 2). During my doctoral and postdoctoral training, I was also involved in another project to decipher mechanisms of resistance to immunotherapy, the results were published in Immunity with me as the second author (3). I thus gained strong training and expertise in tumor immunology and novel immune monitoring technologies.

Three years ago, I joined the Dhanasekaran Lab to deepen my expertise in immuno-oncology. I have gained proficiency in advanced technologies such as CyTOF, spatial immunology and organoids. I have published a manuscript discussing macrophage-mediated mechanisms of resistance to immune checkpoint inhibitors (4, co-author, Cancer Res, 2023) and an article identifying novel mechanisms of resistance to therapy in liver cancer (5, first author, Nat Cancer, 2024). These papers serve as a cornerstone for my current application to develop a precision oncology platform for immunotherapy in HCC. Alongside my mentor, I have crafted a comprehensive career development plan aimed at enhancing my abilities in grant writing, mentoring, teaching, and communication.

1. Lea Lemaitre, DoSouto Ferreira L, Joubert MV, Avet-Loiseau H, Martinet L, Corre J, Couderc Imprinting of Mesenchymal Stromal Cell Transcriptome Persists even after Treatment in Patients with Multiple Myeloma. Int J Mol Sci. 2020 May 28.
2. Lea Lemaitre, Hamaidia M, Descamps JG, Do Souto Ferreira L, Joubert MV, Gadelorge M, Avet-Loiseau H, Justo A, Reina N, Deschaseaux F, Martinet L, Bourin P, Corre J, Espagnolle N. Toll-like receptor 4 selective inhibition in medullary microenvironment alters multiple myeloma cell growth. Blood advance. 2022 Jan 25; 6(2):672-678.
3. Weulersse M*, Asrir A*, Pichler AC*, Lemaitre Lea, Braun M, Carrié N, Joubert MV, Le Moine M, Do Souto L, Gaud G, Das I, Brauns E, Scarlata CM, Morandi E, Sundarrajan A, Cuisinier M, Buisson L, Maheo S, Kassem S, Agesta A, Pérès M, Verhoeyen E, Martinez A, Mazieres J, Dupré L, Gossye T, Pancaldi V, Guillerey C, Ayyoub M, Dejean AS, Saoudi A, Goriely S, Avet-Loiseau H, Bald T, Smyth MJ, Martinet L.. ** co-authors. Eomes-Dependent Loss of the Co-activating Receptor CD226 Restrains CD8 + T Cell Anti- tumor Functions and Limits the Efficacy of Cancer Immunotherapy. Immunity. 2020 Oct 13.
4. Renumathy Dhanasekaran, Aida Hansen, Jangho Park, Lea Lemaitre, Nia Adeniji, Sibu Kuruvilla, Akanksha Suresh, Josephine Zhang, Varsha Swamy, Dean W. Felsher. MYC overexpression drives immune evasion in hepatocellular carcinoma (HCC) that is reversible through restoration of pro- inflammatory macrophages. Cancer research. 2022 Dec 16.
5. Lea Lemaitre*, Nia Adeniji*, Akanksha Suresh*, Reshma Reguram, Josephine Zhang, Jangho Park, Amit Reddy, Alexandro E. Trevino, Aaron T. Mayer, Anja Deutzmann, Aida Hansen, Ling Tong, Vinodhini Arjunan, Neeraja Kambham, Brendan Visser, Monica Dua, Andrew Bonham, Nishita Kothary, H. Blaize D’Angio, Ryan Preska, Yanay Rosen, James Zou, Vivek Charu, Dean W. Felsher and Renumathy Dhanasekaran. Spatial Analysis Reveals Targetable Macrophage-Mediated Mechanisms of Immune Evasion in Hepatocellular Carcinoma Minimal Residual Disease. Nature cancer. 2024 Sept 20