Tumors evade immune destruction by actively inducing immune tolerance through the recruitment of CD4+CD25+Foxp3+ regulatory T cells (Treg). We have previously described increased prevalence of these cells in pancreatic adenocarcinoma, but it remains unclear what mechanisms are involved in recruiting Treg into the tumor microenvironment. Here, we postulated that chemokines might direct Treg homing to tumor. We show, in both human pancreatic adenocarcinoma and a murine pancreatic tumor model (Pan02), that tumor cells produce increased levels of ligands for the CCR5 chemokine receptor, and, reciprocally, that CD4+ Foxp3+ Treg, compared with CD4+ Foxp3− effector T cells, preferentially express CCR5. When CCR5/CCL5 signaling is disrupted, either by reducing CCL5 production by tumor cells or by systemic administration of a CCR5 inhibitor (TAK-779), Treg migration to tumors is reduced and tumors are smaller than in control mice. Thus, this study demonstrates the importance of Treg in immune evasion by tumors, how blockade of Treg migration may inhibit tumor growth, and, specifically in pancreatic adenocarcinoma, the role of CCR5 in the homing of tumor-associated Treg. Selective targeting of CCR5/CCL5 signaling may represent a novel immunomodulatory strategy for the treatment of cancer.

Objective To determine the prognostic significance of histologic type/subtype in a large series of patients with primary resected retroperitoneal sarcoma. Summary Background Data The histologic diversity and rarity of retroperitoneal sarcoma has hampered the ability to predict patient outcome. Methods From a single-institution, prospective database, 675 patients treated surgically for primary, non-metastatic retroperitoneal sarcoma during 1982–2010 were identified and histologic type/subtype was reviewed. Clinicopathologic variables were analyzed for association with disease-specific death (DSD), local recurrence (LR), and distant recurrence (DR). Results Median follow-up for survivors was 7.5 years. The predominant histologies were well-differentiated liposarcoma, dedifferentiated liposarcoma, and leiomyosarcoma. Five-year cumulative incidence of DSD was 31%, and factors independently associated with DSD were R2 resection, resection of ≥3 contiguous organs, and histologic type. Five-year cumulative incidence for LR was 39% and for DR was 24%. R1 resection, age, tumor size, and histologic type were independently associated with LR; size, resection of ≥3 organs, and histologic type were independently associated with DR. Liposarcoma and leiomyosarcoma were associated with late recurrence and DSD (as long as 15 years from diagnosis). For solitary fibrous tumor, local recurrence was uncommon (<10%), but early distant recurrence was common (36% at 5 years). Nomograms were developed to predict DSD, LR, and DR. Conclusions Histologic type/subtype is the most important independent predictor of DSD, LR, and DR in primary retroperitoneal sarcoma. Histology predicts the pattern and incidence of LR and DR and will aid in more accurate patient counseling and selection of patients for adjuvant therapy trials.

Background Intraductal papillary mucinous neoplasms (IPMN) are being increasingly recognized as important precursors to pancreatic adenocarcinoma. Elucidation of the genetic changes underlying IPMN carcinogenesis may improve the diagnosis and management of IPMN. We sought to determine whether different histologic subtypes of IPMN would exhibit different frequencies of specific genetic mutations. Study Design Patients with resected IPMN-associated invasive carcinoma (IPMN-INV) between 1997 and 2012 were reviewed. Areas of carcinoma, high-grade dysplasia and low-grade dysplasia were micro-dissected from each pathologic specimen. Targeted, massively-parallel sequencing was then performed on a panel of 275 genes (including KRAS, GNAS and RNF43). Results 38 patients with resected IPMN-INV and sufficient tissue for microdissection were identified. Median follow-up was 2.6 years. GNAS mutations were more prevalent in colloid-type IPMN-INV than tubular-type IPMN-INV, 89% vs 32% respectively (p=0.0003). Conversely, KRAS mutations were more prevalent in tubular-type than colloid-type IPMN-INV, 89% vs 52%, respectively (p=0.01). For non-invasive IPMN subtypes, GNAS mutations were more prevalent in intestinal (74%) compared with pancreatobiliary (31%) and gastric (50%) subtypes (p=0.02). The presence of these mutations did not vary according to the degree of dysplasia (GNAS: invasive 61%, high-grade 59%, low-grade 53%, KRAS: invasive 71%, high-grade 62%, low-grade 74%), suggesting that mutations in these genes occur early in IPMN carcinogenesis. Conclusions IPMN-associated colloid carcinoma and its intestinal-type pre-invasive precursor are associated with high frequencies of GNAS mutations. The mutation profile of tubular carcinoma resembles conventional pancreatic adenocarcinoma. Preoperative determination of mutational status may assist with clinical treatment decisions.

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CD4+25+Foxp3+ regulatory T cells (Treg) play a critical role in the induction of tolerance to tumor associated antigens and suppression of anti-tumor immunity. How Treg are induced in cancer is poorly understood. We reported previously that Treg are significantly elevated in the peripheral blood of patients with pancreas cancer and that in a murine pancreas cancer model induction of Treg appears to be TGF-Beta dependent. Here we provide additional evidence that Treg are increased locally within the tumor microenvironment by a mechanism that appears dependent on TGF-Beta Receptor expression and the presence of tumor derived TGF-Beta. The murine pancreas cancer cell line Pan02 produces high levels of TGF-Beta both in vitro and in vivo. In contrast, the esophageal murine cancer cell line, Eso2, does not. Immunohistochemical staining of Foxp3 in explanted tumors shows an identifiable population of Treg in the Pan02 (TGF-Beta positive) tumors but not Eso2 (TGF-Beta negative). Naïve CD4+25−Foxp3− T cells, when adoptively transferred into Rag−/− mice, are converted into Foxp3+ Treg in the presence of Pan02 but not Eso2 tumors. Induction of Treg in Pan02 mice is blocked by systemic injection of an anti-TGF-Beta antibody. If Rag−/− mice are instead reconstituted with naïve CD4+25− T cells expressing a mutated TGF-Beta receptor, induction of Foxp3+ Treg in Pan02 bearing mice is blocked. Collectively these observations further support the role of TGF-Beta in the induction of Treg in pancreas adenocarcinoma.

Dramatic responses are being observed in colorectal cancer liver metastases treated with newer chemotherapeutic regimens. These have been associated with normalization of [(18)F]fluoro-2-deoxy-D-glucose (FDG) uptake (complete metabolic response) on follow-up Positron Emission Tomography with [(18)F]fluoro-2-deoxy-D-glucose (FDG-PET) scans in some patients. It is unclear how often complete metabolic response is indicative of complete tumor destruction. We analyzed a subset of patients who had neoadjuvant chemotherapy for hepatic metastases from colorectal adenocarcinoma. Inclusion criteria were: (1) FDG-avid hepatic lesions before initiation of chemotherapy; (2) complete metabolic response of the same lesions after chemotherapy; and (3) histopathologic examination of hepatic lesions. Complete pathologic response was defined as no histologically identifiable viable tumor. Fourteen patients fit the inclusion criteria. All had synchronous, hepatic-only colorectal metastases. On microscopic examination, complete pathologic response to the neoadjuvant regimen was found in only 5 of 34 lesions (15%) and in only 3 of the 14 patients (21%). Seven lesions had complete metabolic response and disappeared on computed tomography (CT); of these, six still contained viable tumor. We conclude that complete metabolic response on FDG-PET after neoadjuvant chemotherapy is an unreliable indicator of complete pathologic response. Therefore, currently, curative resection of liver metastases in these patients should not be deferred on the basis of FDG-PET findings.

Recent studies describe a heterogeneous population of cells of the myeloid lineage, termed myeloid derived suppressor cells (MDSC), which are observed with increased prevalence in the peripheral blood and tumor microenvironment of cancer patients, including pancreatic cancer. Accumulation of MDSC in the peripheral circulation has been related to extent of disease, and correlates with stage. MDSC have primarily been implicated in promoting tumor growth by suppressing antitumor immunity. There is also compelling evidence MDSC are also involved in angiogenesis and metastatic spread. Two main subsets of MDSC have been identified in cancer patients: a monocytic subset, characterized by expression of CD14, and a granulocytic subset characterized by expression of CD15. Both subsets of MDSC actively suppress host immunity through a variety of mechanisms including production of reactive oxygen species and arginase. Just as in humans, accumulation of monocytic and granulocytic MDSC has been noted in the bone marrow, spleen, peripheral circulation, and tumors of tumor bearing mice. Successful targeting of MDSC in mice is associated with improved immune responses, delayed tumor growth, improved survival, and increased efficacy of vaccine therapy. By further elucidating mechanisms of MDSC recruitment and maintenance in the tumor environment, strategies could be developed to reverse immune tolerance to tumor. We discuss here what is currently known about MDSC as well as some potential strategies targeting MDSC in the context of our work on pancreatic cancer and recent literature. Due to the number of new reports on MDSC, the most pertinent ones have been selected.

Objectives Exosomes are important mediators in intercellular communications and play a role in cancer progression and metastasis. Exosomal membranes are enriched in endosome-specific tetraspanins (CD9 and CD63). Here, we explored the expression of CD63 and CD9 utilizing immunohistochemistry in malignant and non-malignant cells in 29 resected pancreatic specimens (RPS) of mixed racial background. Methods The pathologic tissues (PTs) and adjacent normal tissues (ANTs) in each RPS were stained for CD63 and CD9. Two pathologists independently scored the expression of CD63 and CD9. Staining intensity was graded from 1–3. Staining percentage was estimated in 10% increments. An average Q score (Intensity X Percentage of staining) was calculated. Unpaired t test was used for statistical analysis. Results The mean multiplicative Quick-score (Q-score) for CD63 and CD9 expression is higher in PTs (209 and 72) compared to ANTs (154 and 24) (p= 0.0041; p=0.0018). The Mean Q score for CD63 and CD9 expression is higher in the malignant PTs (231 and 85) compared to ANTs (129 and 25) (p<0.0001 and p < 0.0124). Conclusions Exosomal markers (CD63 and CD9) expression assessment using IHC is feasible in RPS. The expression of CD63 and CD9 is higher in PTs and malignant PTs compared to their ANT.