Vaccine against MUC1 antigen expressed in inflammatory bowel disease and cancer lessens colonic inflammation and prevents progression to colitis-associated colon cancer

Abstract

Association of chronic inflammation with an increased risk of cancer is well established, but the contributions of innate versus adaptive immunity are not fully delineated. There has furthermore been little consideration of the role played by chronic inflammation-associated antigens, including cancer antigens, and the possibility of using them as vaccines to lower the cancer risk. We studied the human tumor antigen MUC1 which is abnormally expressed in colon cancers and also in inflammatory bowel disease (IBD) that gives rise to colitis-associated colon cancer (CACC). Using our new mouse model of MUC1(+) IBD that progresses to CACC, interleukin-10 knockout mice crossed with MUC1 transgenic mice, we show that vaccination against MUC1 delays IBD and prevents progression to CACC. One mechanism is the induction of MUC1-specific adaptive immunity (anti-MUC1 IgG and anti-MUC1 CTL), which seems to eliminate abnormal MUC1(+) cells in IBD colons. The other mechanism is the change in the local and the systemic microenvironments. Compared with IBD in vaccinated mice, IBD in control mice is dominated by larger numbers of neutrophils in the colon and myeloid-derived suppressor cells in the spleen, which can compromise adaptive immunity and facilitate tumor growth. This suggests that the tumor-promoting microenvironment of chronic inflammation can be converted to a tumor-inhibiting environment by increasing adaptive immunity against a disease-associated antigen.

Figure 1

Vaccination of MUC1⁺/IL-10^−/− mice with a MUC1 vaccine slows down IBD development and decreases intestinal inflammation. (A) Kaplan-Meir curves representing development of rectal prolapse in vaccinated (solid line, n=19), adjuvant treated (dotted line, n=16) or untreated (gray line, n=34) mice. Arrows indicate administration of the vaccine or adjuvant alone at 6, 8, and 10 weeks of age. * p=0.043. P value was determined by the log-rank test. (B) Colonic inflammation scores formice that received vaccine (n=8), adjuvant alone (n=9), or remained untreated (n=13), sacrificed at 16 weeks of age. * p=0.015. P value was determined by unpaired two-tailed Student’s t test. (C) Representative H&E sections of colons from an untreated, an adjuvant treated, and a vaccinated MUC1⁺/IL-10^−/− mouse. Scale bar, 50 μm.

Figure 2

MUC1-specific immune responses in vaccinated versus control MUC1⁺/IL-10^−/− mice. (A) MUC1-specific antibodies in serum of untreated (n=6), adjuvant treated (n=4), and vaccinated (n=7) mice. IgM isotype, top panel; IgG isotype, bottom panel; Optical Density (O.D.) measured by ELISA at 450 nm. Serum samples were diluted 1:50. P value was determined by unpaired two-tailed Student’s t test. (B) Splenocytes from untreated, adjuvant treated, or vaccinated MUC1⁺/IL-10^−/− mice were stained with MUC1 peptide loaded H2Kb-Ig dimer. Representative dot plots from two independent experiments. (C) Results of standard ⁵¹Cr release assay at an effector:tumor cell (E:T) ratio of 50:1. Effector cells are pooled lymph node (LN) from two mice per group. Targets are RMA (H2Kb) or RMA-MUC1 (H2Kb), transfected with human MUC1 cDNA. (D) Immunostaining (hematoxylin counterstained) of colon sections with anti-MUC1 antibodies. Scale bar, 50μm.

Figure 3

Vaccination against MUC1 prevents the development of dysplasia and CACC. (A) Percentage of untreated (n=13) and adjuvant treated (n=9) mice with dysplasia at 16 weeks of age. Vaccinated mice (n=8) had no areas of dysplasia. *, p=0.046. P value was determined by two-tailed Fisher’s exact test. (B) Representative H&E stained colon sections showing dysplastic lesions. Scale bar, 50μm. (C) Percentage of untreated (n=16), adjuvant treated (n=6), or vaccinated (n=10) mice with tumors. *, p= 0.041. P value was determined by two-tailed Fisher’s exact test. (D) Representative colon section showing multiple tumors in the colon of an untreated mouse. Immunostaining (hematoxylin counterstained) for MUC1 of a representative colon tumor from an untreated mouse. Scale bar, 100μm.

Figure 4

Vaccination induces changes in the local and systemic microenvironments of MUC1⁺/IL-10^−/− mice with IBD. (A) Representative H&E sections of colons from an untreated, an adjuvant treated, and a vaccinated MUC1⁺/IL-10^−/− mouse. Scale bar, 100 μm. Inserts are oil immersion magnification ×1000 and show infiltration of neutrophils (lobular shaped nuclei and copious cytoplasm) in the colons of untreated and adjuvant treated mice and infiltration of lymphocytes (small round nuclei and little cytoplasm) in colons of vaccinated mice. (B) Neutrophil-produced lactoferrin levels in the feces collected at 4, 8, 10, and 16 weeks of age in vaccinated (n=7), adjuvant treated (n=6), and untreated (n=5) MUC1⁺/IL-10^−/− mice, as measured by ELISA. (C) MDSC (Gr1⁺CD11b⁺) in spleens of indicated experimental groups. Representative dot plots of several independent experiments.