Immunity as the predominant factor determining metastasis by murine lymphomas

Area of Science:

• Immunology
• Oncology
• Cancer Metastasis Research

Background:

• The L5178E (non-M) lymphoma and its highly metastatic subline L51787ES (M) were utilized to investigate metastatic behavior.
• Tumorigenicity and metastatic potential are key factors in cancer progression and treatment strategies.
• Understanding the interplay between tumor cells and the host immune system is crucial for deciphering metastasis.

Purpose of the Study:

• To elucidate the factors influencing the metastatic behavior of L5178E lymphoma and its metastatic subline in syngeneic mice.
• To determine the role of host immunological responses versus intrinsic tumor cell properties in cancer metastasis.
• To investigate the impact of host irradiation on tumor metastasis and immune cell infiltration.

Main Methods:

• Transplantation of L5178E (non-M) and L51787ES (M) lymphoma sublines into intact and irradiated syngeneic DBA2 mice.
• Assessment of metastatic potential through observation of tumor growth and metastasis formation.
• Evaluation of immunogenicity using conventional transplantation criteria and a lymph node weight-gain assay.
• Analysis of host-cell infiltration into subcutaneous tumors and in vitro characterization of infiltrating cells.

Main Results:

• The non-M tumor rarely metastasized in intact mice but showed extensive, lethal metastasis in irradiated recipients.
• Host irradiation did not affect the metastatic behavior of the highly metastatic M subline.
• The non-M tumor was more immunogenic than the M subline, with greater host-cell infiltration (macrophages) in non-M tumors.
• Despite higher in vitro motility of M cells, metastatic behavior was primarily dictated by host immunological responses.

Conclusions:

• Host immunological status significantly influences the metastatic potential of tumors, overriding intrinsic tumor cell characteristics like motility.
• Irradiation of the host can abrogate anti-tumor immunity, thereby promoting metastasis of less aggressive tumor variants.
• Macrophage infiltration plays a role in the host's control over tumor metastasis.