A20: Modelos para linfoma de células B en ratones

Los investigadores están usando modelos de ratones preclínicos en un esfuerzo por emplear métodos de tratamiento convencionales para linfoma  —como radioterapia y quimioterapia— en combinación con agentes inmunomoduladores para tratar con mayor eficacia esta enfermedad. Covance ha desarrollado el modelo tumoral A20 singeneico, un linfoma de células B, para trabajar con estas aplicaciones de inmuno-oncología.

AUTOR:

Sheri Barnes, PhD, Director, Scientific Development

FECHA:

Octubre de 2017

Lymphomas represent a highly heterogenous set of lymphoid cell malignancies. They can originate from either B or T cells, but B cell-derived lymphomas, specifically non-Hodgkin lymphoma (NHL), are the most prevalent. Lymphomas can be diagnosed in children and adolescents, but incidence of lymphoma increases significantly with age, the median age of diagnosis being 67 years. Se estima que en el 2017 se diagnosticarán 72.240 nuevos casos de LNH en los Estados Unidos y 20.140 pacientes fallecerán a causa de esta enfermedad. While the five-year survival rate for NHL is relatively high at 71 %, recurrence can occur most often within five years of treatment,1 making the development of new treatment strategies for lymphoma essential for long term survival of these patients.

Given the impact of immunotherapy in other cancers, researchers are using preclinical mouse modeling in an effort to employ conventional treatment methods for lymphoma, such as radiotherapy and chemotherapy, in combination with immunomodulatory agents to more effectively treat this disease. Covance ha desarrollado el modelo tumoral A20 singeneico, un linfoma de células B, para trabajar con estas aplicaciones de inmuno-oncología. A20 was derived from a spontaneously arising reticulum cell sarcoma from an aging Balb/c mouse.2 A20 tumors are reported to express high levels of PD-L13 and are responsive to immunomodulatory antibodies. Taken together, A20 is an attractive model for use in immunotherapy drug development.

The doubling time of A20 is ~4-5 days, a moderate growth rate relative to other syngeneic models, potentially facilitating a longer dosing duration for test agents to elicit their anti-tumor activity. Figure 1 demonstrates median (1A) and individual (B-E) growth of control tumors compared to those treated with an immunomodulatory antibody. With dosing initiated on Day 3 after implant for the checkpoint inhibitors anti-PD-1 and anti-PD-L1, and on Day 10 after implant for the agonist anti-GITR, the anti-tumor response is striking. We expect that initiating dosing with these agents once A20 tumors are palpable will allow room for improvement in combination with candidate molecules.

Fig. 1: Median and Individual Growth of A20 Tumors Following Immunotherapy

Fig. 1: Median and Individual Growth of A20 Tumors Following Immunotherapy

 

To investigate immunomodulatory effects of anti-GITR on the A20 tumor, we analyzed T cell and myeloid cell populations in tumor one week post-treatment. The results are illustrated in Figure 2. With anti-GITR treatment, the CD8+/Treg ratio increases dramatically (Fig. 2A). This increase indicates engagement of the host immune system which is also reflected in tumor burden decreases (Fig. 1). In contrast, changes in myeloid cell populations were modest. While some myeloid cell populations were unchanged with treatment, trends toward a decrease in %M-MDSC accompanied by an increase in %M1 macrophages are evident with anti-GITR treatment compared with isotype control (Fig. 2B).

Fig. 2: Immunoprofiling of A20 Tumors Following Anti-GITR Treatment

Fig. 2: Immunoprofiling of A20 Tumors Following Anti-GITR Treatment

 

In addition to the promise of immunotherapy, radiation therapy is often used in the course of lymphoma treatment clinically and is typically administered in combination with other agents. Covance employs the Small Animal Radiation Research Platform (SARRP) by XStrahl for modeling focal beam radiation (see our related blog and poster), and we investigated a single dose range of 5-20 Gy against A20 tumors. Median (Figure 3A) and individual (Figure 3B-E) tumor growth following this treatment are illustrated below. A20 tumors are impacted by radiation at all doses, and two mice each at the 10 and 20 Gy dose levels had durable complete responses almost 70 days post implant. These animals remained tumor free despite a rechallenge with a second injection of A20 cells, while tumors grew as expected in naïve age-matched animals (data not shown).

Fig. 3: Median and Individual Growth Curves of A20 Tumors Following Focal Beam Radiation

Fig. 3: Median and Individual Growth Curves of A20 Tumors Following Focal Beam Radiation

 

The A20 model provides robust preclinical means by which to study B cell lymphoma. The responsiveness of A20 to checkpoint inhibitors, costimulatory immunoagonists, and radiotherapy makes it an attractive model for use in the preclinical immuno-oncology space. Please contact Covance to speak with our scientists about how A20 or one of our other syngeneic models can be used for your next immuno-oncology study.

1Howlader N, Noone AM, Krapcho M, Miller D, Bishop K, Kosary CL, Yu M, Ruhl J, Tatalovich Z, Mariotto A, Lewis DR, Chen HS, Feuer EJ, Cronin KA (eds). SEER Cancer Statistics Review, 1975-2014, National Cancer Institute. Bethesda, MD, https://seer.cancer.gov/csr/1975_2014/, según la presentación de datos de SEER de noviembre de 2016, publicado en el sitio web de SEER en abril de 2017.

2Kim KJ, Kanellopoulos Langevin C, Merwin RM, Sachs DH, Asofsky R (1979) Establishment and characterization of BALB/c lymphoma lines with B cell properties.  Journal ofImmunology, 122(2): 549–554.

3Sagiv-Barfi I, Kohrt HEK, Czerwinski DK, Ng PP, Chang BY, Levy L (2015) Therapeutic antitumor immunity by checkpoint blockade is enhanced by ibrutinib, an inhibitor of both BTK and ITK.  PNAS, 112(9): E966-E972.

Nota: Los estudios se realizaron de conformidad con la normativa de bienestar animal vigente en un establecimiento con acreditación de AAALAC