마우스 악성 흑색종의 실험적 폐전이에 대한 Monophosphory Lipid A, Polyadenylic-polyuridylic Acid 및 Cisplatin의 항암효과

Abstract

[한글]

종양에 대한 숙주의 방어기전은 주로 세포매개성 면역반응에 의해 유도되는 세포독성 T 림프구(cytotoxic T lymphocyte: CTL), 자연살(natural killer: NK) 세포, 림포카인 활성살(lymphokine activated killer: LAK) 세포, 종양침윤 림프구(tumor infiltrating lymphocyte: TIL) 및 대식세포의 세포독성 작용이 중요한 역활을 하는 것으로 알려져 있다.

이러한 사실에서 근래에는 이 세포들, 특히 LAK 및 TIL 세포를 interleukin(IL)-2로 시험관내에서 증식 및 활성화시켜 IL-2와 함께 종양환자에 재투여하는 자가입양 면역요법(autologous adoptive immunotherapy)이 시도되었고, 이 방법이 일부 환자에서는 임상적 치료 효과가 있음이 보고되었다. 그러나 이들 세포의 지속적인 성장과 세포독성능 유지를 위한 IL-2의 대량투여가 높은 부작용을 유발하고, 또한 몇몇 종양의 유형에만 치료효과가 있기 때문에 이 요법은 많은 문제가 제기되고 있다.

Monophosphoryl lipid A(MPL)는 endotoxin인 lipopolysaccharide(LPS)의 유도체로서 독성이 매우 낮고 LPS와 매우 유사하게 면역반응을 증가시키며 특히 대식세포를 활성화시키는 동시에 interferon(IFN)-γ의 생성도 증가시키는 것으로 알려져 있다. 한편 polyadenylic-polyuridylic acid[poly(A)·poly(U))는 합성중합 핵산물질로 주로 T 세포에 작용하여IFN-γ의 생성을 증가시킴으로서 NK 세포의 세포 독성능을 증강시키는 것으로 보고되고 있다.

이에 본 연구에서는 MPL, poly(A)· Poly(U) 및 항암제인 cisplatin을 단독 혹은 병용투여하여 마우스 악성 흑색종의 실험적 폐전이에 미치는 항종양효과를 관찰하고 그 작용기전을 규명하고자 하였다.

1. MPL, poly(A) · poly(U) 및 cisplatin 투여군은 대조군에 비해 전이성 폐암 형성이 현저히 억제되었다.

2. Cisplatin과 MPL 또는 Poly(A)·Poly(U)의 병용투여는 병용효과가 없었으나, MPL 및 Poly(A) · poly(U)에 의한 항암효과는 단독투여보다 병용투여가 증가하는 경향을 보였다.

3. 생체내 MPL 및 Poly(A)· poly(U)의 투여시 비장 림프구의 세포독성능은 YAC-1 및 악성 흑색종세포에 대해 모두 증가하는데 반하여, 대식세포의 세포독성능은 YAC-1에 대해서만 증가하는 것으로 나타났다. 그리고 그 효과는 MPL 투여군이 Poly(A)· Poly(U) 투여

군보다 더 높은 것으로 나타났다.

한편 시험관내에서 MPL 및 poly(A)· Poly(U)의 자극은 비장 림프구 및 대식세포의 세포독성능을 증가시키지 못하였다.

4. 리장 림프구의 IL-2 및 IFN-γ의 생성은 MPL 및 po1y(A)· poly(U) 투여군에서 대조군에 비해 현저히 증가하였으며, MPL 투여군이 poly(A)·poly(U) 투여군보다 높은 증가를 보였다.

이들 세포의 IL-4의 생성은 poly(A)· poly(U) 투여군과 대조군사이에는 차이가 없었으며, MPL 투여군에서는 오히려 현저히 감소하였다.

이상의 결과를 종합하여 볼때 마우스에 있어서 MPL 및 poly(A)· poly(U) 투여는 악성 흑색종의 실험적 폐전이를 억제하는 것으로 나타났으며, 이들의 억제현상은 림프구의 IL-2 및IFN-γ의 생성을 증가시켜, NK 세포 및 대식세포의 세포독성능의 증가에 의해 기인된

것으로 생각된다. 특히 MPL이 poly(A)· poly(U)보다 높은 암 억제 효과를 나타내는 경향을 보이며, 세포 매개성 면역기능에 관여하는 IL-2 및 IFN-γ의 생성을 현저하게 증가시키는 점을 고려할때, 향후 유용한 면역치료제로 쓰일 수 있을 것으로 사료된다.

Antltumor effect of monophosphoryl lipid A, polyadenylic-polyuridylic acid and

cisplatin on B16 melanoma-induced pulmonary metastasis in mice

Chul Ho Cho

Department of Medical science The Graduate School, Yonsei University

(Directed by Professor Joo Deuk Kim)

Despite aggressive surgery, radiation and combined chemotherapy, recurrence after

treatment of primary cancer is common. Complete eradication of cancer cells with

these modalities is hard, if at all, to achieve.

Immunity is usually depressed in hosts with tumor and a strong relationship

exists between immunocompetence and prognosis of cancer. Immunotherapy thus aims at

stimulating natural host defense mechanism to facilitate tumor regression.

Augmentation of natural killer(NK) cell cytotoxicity, macrophage activation, and

interferon (IFN)-γ-mediated T Iymphocyte proliferation are believed to be the main

antitumor effects of immunotherapy.

Monophosphoryl lipid A(MPL), a derivative of lipopolysaccharide(LPS), which has

antitumor activity with low toxicity, has been shown to enhance antibody production

with increased IFN-γ in both young adult and aging mice. Polyadenylic-polyuridrlic

acid[poly(A) · poly(U)] is a nontoxic and metabolically stable immunomodulator,

capable of efficiently stimulating various compartments of host-immune system,

thereby enhancing their antitumor activity. It has been successfully used in

adjuvant treatment of human breast and stomach cancer, increasing patient survival

and decreasing recurrence. This study looted into antitumor effects of MPL, poly(A)

· poly(U) and cisplatin, used alone or in combination, against Bl6 melanoma lung

metastasis in mice, and the following results were obtained:

1) Antitumor effects of MPL, poly(A) · poly(U) and cisplatin were significantly

higher in the mice treated with these agents than the saline-treated controls.

2) The combined use of MPL and poly(A) · poly(U) tended to show, though not

significant, higher antitumor effect than the sole use of either MPL or poly(A) ·

poly(U) in mice not previously treated with cisplatin, but not in mice pretreated

with cisplatin.

3) In vivo inoculation of MPL and poly(A) · poly(U) significantly enhanced

cytotoxicity of spleen cells against both YAC-1 cells and Bl6 melanoma cells, but

enhanced cytotoxicity of peritoneal macrophages only against the former(YAC-1

cells). In vitro, it failed to increase cytotoxicity of either spleen cells or

peritoneal macrophages.

4) In vivo IL-2 and IFN-γ Production were significantly higher in the mice

treated with MPL or poly(A)·poly(U) than the controls with the production in the

mice treated with MPL higher than with poly(A)·poly(U). IL-4 production in vivo

was not different between the mice treated with poly(A)·poly(U) and the controls,

but in the MPL-treated mice, it was significantly lower than in the controls.

Antitumor activity of MPL and Poly(A)·Poly(U) against metastatic lung cancer

appears to arise from increased cytotoxicy of NK cells and macrophages, mediated by

the increased IL-2 and IFN-γ production. In Particular, compared with

poly(A)·poly(B), MPL, the substance showing as in this study a high antitumor

effect and significantly increased production of IL-2 and IFN-γ, the cytokines

believed to be important in cell-mediated immunity, appears premising as a

potentially useful immunotherapeutic agent.

[영문]

Despite aggressive surgery, radiation and combined chemotherapy, recurrence after treatment of primary cancer is common. Complete eradication of cancer cells with these modalities is hard, if at all, to achieve.

Immunity is usually depressed in hosts with tumor and a strong relationship exists between immunocompetence and prognosis of cancer. Immunotherapy thus aims at stimulating natural host defense mechanism to facilitate tumor regression.

Augmentation of natural killer(NK) cell cytotoxicity, macrophage activation, and interferon (IFN)-γ-mediated T Iymphocyte proliferation are believed to be the main antitumor effects of immunotherapy.

Monophosphoryl lipid A(MPL), a derivative of lipopolysaccharide(LPS), which has antitumor activity with low toxicity, has been shown to enhance antibody production with increased IFN-γ in both young adult and aging mice. Polyadenylic-polyuridrlic acid[poly(A) · poly(U)] is a nontoxic and metabolically stable immunomodulator, capable of efficiently stimulating various compartments of host-immune system, thereby enhancing their antitumor activity. It has been successfully used in adjuvant treatment of human breast and stomach cancer, increasing patient survival and decreasing recurrence. This study looted into antitumor effects of MPL, poly(A) · poly(U) and cisplatin, used alone or in combination, against Bl6 melanoma lung metastasis in mice, and the following results were obtained:

1) Antitumor effects of MPL, poly(A) · poly(U) and cisplatin were significantly higher in the mice treated with these agents than the saline-treated controls.

2) The combined use of MPL and poly(A) · poly(U) tended to show, though not significant, higher antitumor effect than the sole use of either MPL or poly(A) · poly(U) in mice not previously treated with cisplatin, but not in mice pretreated

with cisplatin.

3) In vivo inoculation of MPL and poly(A) · poly(U) significantly enhanced cytotoxicity of spleen cells against both YAC-1 cells and Bl6 melanoma cells, but enhanced cytotoxicity of peritoneal macrophages only against the former(YAC-1 cells). In vitro, it failed to increase cytotoxicity of either spleen cells or peritoneal macrophages.

4) In vivo IL-2 and IFN-γ Production were significantly higher in the mice treated with MPL or poly(A)·poly(U) than the controls with the production in the mice treated with MPL higher than with poly(A)·poly(U). IL-4 production in vivo was not different between the mice treated with poly(A)·poly(U) and the controls, but in the MPL-treated mice, it was significantly lower than in the controls.

Antitumor activity of MPL and Poly(A)·Poly(U) against metastatic lung cancer appears to arise from increased cytotoxicy of NK cells and macrophages, mediated by the increased IL-2 and IFN-γ production. In Particular, compared with poly(A)·poly(B), MPL, the substance showing as in this study a high antitumor

effect and significantly increased production of IL-2 and IFN-γ, the cytokines believed to be important in cell-mediated immunity, appears premising as a potentially useful immunotherapeutic agent.