Inhibition of host signal transducer and activator of transcription factor 6 results in cure with cyclophosphamide and interleukin 12 immunotherapy.

BACKGROUND: Interleukin (IL)-12 immunotherapy is highly effective against established immunogenic tumors. However, nonimmunogenic tumors fail to respond to IL-12 therapy. Analysis of tumor rejection of the immunogenic tumors shows that a preexisting antitumor immune response is required for an effective IL-12 response. It is not known whether this lack of a preexisting host antitumor immune response is a limiting factor for the lack of response to IL-12 therapy by nonimmunogenic tumors. METHODS: Experiments were done using the spontaneously arising nonimmunogenic metastatic murine breast 4T1 carcinoma in normal and STAT6 knockout BALB/c mice. RESULTS: 4T1 is nonimmunogenic in normal mice, and established subcutaneous tumors are resistant to immunotherapy with cyclophosphamide (Cy) plus IL-12. However, in STAT6 knockout mice, 4T1 becomes immunogenic, and established 4T1 tumors are eradicated by Cy plus IL-12. Adoptive transfer of spleen cells from normal mice into STAT6 knockout mice before tumor inoculation reduces both the immunogenicity and response to Cy plus IL-12 immunotherapy of 4T1 in the recipient mice. CONCLUSIONS: Cy plus IL-12 immunotherapy can eradicate nonimmunogenic tumors as long as a preexisting immunity is established in the tumor-bearing host. Furthermore, the STAT6 pathway is likely involved in the suppression of the development of host antitumor immunity.

Production of interferon-gamma by tumor-sensitized T cells is essential for interleukin-12-induced complete tumor eradication.

BACKGROUND: Interferon-gamma (IFN-gamma) is essential for eradication of established large tumors by interleukin-12 (IL-12), but the critical source of IFN-gamma has not been defined. Adoptive transfer of T cells into T cell-deficient mice allows for evaluation of the role of T cells and T cell production of IFN-gamma in the antitumor immune response. METHODS: Wild-type C57BL/6, IL-12 receptor-beta1 knockout (IL-12Rbeta1 KO), IFN-gamma knockout (IFN-gamma KO), and IFN-gamma receptor-alpha knockout (IFN-gammaRalpha KO) mice were immunized and used as donors for adoptive transfer. Transfer of either splenocytes or CD90(+) T cells was performed into recipient T cell receptor-beta knockout (TCRbeta KO) and IFN-gamma/TCRbeta double knockout mice bearing 14-day subcutaneous MCA207 tumors. Half of the mice were treated with IL-12, and cure rates were compared. RESULTS: Transfer of either 1/4 immunized spleen equivalent or 10(7) immunized T cells into both TCRbeta KO and IFN-gamma/TCRbeta KO mice resulted in 80% to 100% cure when given with IL-12. However, transfer of 10(7) immunized T cells from IFN-gamma KO mice into TCRbeta KO mice was ineffective with or without IL-12. T cell response to IL-12, but not IFN-gamma, was required for tumor regression. CONCLUSIONS: Production of IFN-gamma by IL-12-responsive tumor-sensitized T cells is both necessary and sufficient for complete tumor eradication induced by IL-12. T cells are the source, but not the target, of IFN-gamma during tumor regression.

The role of IFN-gamma in rejection of established tumors by IL-12 : source of production and target.

We have demonstrated previously that established small and large murine MCA207 sarcomas can be completely eradicated by treatment with interleukin (IL) 12 alone and cyclophosphamide plus IL-12 (Cy+IL-12), respectively. The antitumor effect of IL-12/Cy+IL-12 has been found to be dependent on IFN-gamma and T cells. The role of IFN-gamma in IL-12-induced tumor rejection is unclear, because after IL-12 administration IFN-gamma is produced by multiple cell types, and it acts on most cell types because of the ubiquitous expression of its receptor. Using a T-cell-adoptive transfer model, we show that after IL-12 treatment, tumor-specific T-cell production of IFN-gamma is necessary and sufficient for rejection of established tumors. Furthermore, by testing tumors using IFN-gamma-unresponsive tumor cells, we show that tumor cell expression of MHC class I molecules in vivo is abrogated by blocking the response to IFN-gamma. However, tumor response to IFN-gamma is not essential for rejection of established small and large tumors by IL-12 and Cy+IL-12, respectively; neither is it essential for expression of tumor immunogenicity. Our results indicate that the rejection of established tumors by IL-12/Cy+IL-12 is dependent on the induction of a Th1 response producing IFN-gamma that acts on host cells.

Multiple-gland disease in primary hyperparathyroidism: a function of operative approach?

HYPOTHESIS: The approach to surgery for primary hyperparathyroidism (PHPT) is controversial. To determine whether routine bilateral neck exploration increases the detection of multiple-gland disease compared with a focused unilateral approach, we compared the incidence of single vs multiple-gland disease in patients undergoing surgical treatment for PHPT as a function of unilateral or bilateral exploration. DATA SOURCES: From 1993 through 1997, 214 consecutive patients underwent initial bilateral neck exploration for PHPT by a single surgeon. Each patient underwent the surgical procedure without prior localizing studies. Four parathyroid glands were identified, and abnormal glands were excised. The results were compared with published studies of patients who underwent either bilateral neck exploration or focused unilateral neck exploration for PHPT. STUDY SELECTION: All reported studies from 1995 through 2001 in a MEDLINE search using the terms "parathyroidectomy" or "primary hyperparathyroidism and surgery" and either "bilateral" or "conventional" or "minimally invasive," "selective," or "unilateral." DATA EXTRACTION: The studies were analyzed for numbers of patients and a final diagnosis of either a single adenoma or multiple-gland disease (double adenoma or hyperplasia). Proportions were compared statistically with a chi(2) test. DATA SYNTHESIS: In our series of 214 patients who underwent bilateral neck exploration, 79.4% had a single adenoma, and 20.6% had multiple-gland disease. Of 2166 patients in 14 studies who underwent bilateral neck exploration, 79.7% had a single adenoma, and 19.3% had multiple-gland disease. Of 2095 patients in 31 studies with a focused unilateral approach, 92.5% had a single adenoma, whereas only 5.3% had multiple-gland disease. The incidence of multiple-gland disease was significantly lower among patients treated with a focused unilateral approach compared with a bilateral approach as used in our series and the literature (P<.001). CONCLUSION: The data suggest that a focused unilateral surgical approach for PHPT may underestimate the incidence of multiple-gland disease.

Parathyroid hormone-related protein as a novel tumor marker in pancreatic adenocarcinoma.

INTRODUCTION: Parathyroid hormone-related protein (PTHrP) can act as an oncoprotein to regulate the growth and proliferation of many common malignancies, including pancreatic cancer. Previous studies have shown that PTHrP is produced by human pancreatic cancer cell lines, can be shown in the cytoplasm and nucleus of paraffin-embedded pancreatic adenocarcinoma tumor specimens, and is secreted into the media of cultured pancreatic adenocarcinoma cells. We hypothesized that PTHrP could serve as a tumor-marker for growth of pancreatic cancer in vivo. AIM AND METHODOLOGY: To test this hypothesis, we used an orthotopic model developed in our laboratory of the PTHrP-producing human pancreatic cancer line, BxPC-3. This tumor was stably transduced with green fluorescence protein (GFP) to facilitate visualization of tumor growth and metastases. At early (5 weeks) and late (13 weeks) time points after surgical orthotopic implantation, serum PTHrP was measured and primary and metastatic tumor burden was determined for each mouse by assessing GFP expression. RESULTS: By 5 weeks after surgical orthotopic implantation (early group), the mean serum PTHrP level was 33.3 pg/mL. In contrast, by 13 weeks after surgical orthotopic implantation (late group), the mean serum PTHrP level increased to 158.5 pg/mL. These differences were highly significant (p < 0.001, Student t test). Numerous metastatic lesions were readily visualized by GFP in the late group. Serum PTHrP levels measured by immunoassay correlated with primary pancreatic tumor weights and serum calcium levels (p <0.01). PTHrP levels were not detectable (<21 pg/mL) in any of the 10 control mice with no tumor. Western blotting of BxPC-3-GFP tumor lysates confirmed the presence of PTHrP. BxPC-3-GFP tumor tissue stained with antibody to PTHrP. CONCLUSION: These results indicate that PTHrP can serve as a tumor marker in animal models of pancreatic cancer and may be a useful tumor marker for clinical pancreatic adenocarcinoma.