Adjuvant hormonal treatment with peptide YY or its analog decreases human pancreatic carcinoma growth

Neuropeptide Y Peptide Family and Cancer: Antitumor Therapeutic Strategies

Currently available data on the involvement of neuropeptide Y (NPY), peptide YY (PYY), and pancreatic polypeptide (PP) and their receptors (YRs) in cancer are updated. The structure and dynamics of YRs and their intracellular signaling pathways are also studied. The roles played by these peptides in 22 different cancer types are reviewed (e.g., breast cancer, colorectal cancer, Ewing sarcoma, liver cancer, melanoma, neuroblastoma, pancreatic cancer, pheochromocytoma, and prostate cancer). YRs could be used as cancer diagnostic markers and therapeutic targets. A high Y1R expression has been correlated with lymph node metastasis, advanced stages, and perineural invasion; an increased Y5R expression with survival and tumor growth; and a high serum NPY level with relapse, metastasis, and poor survival. YRs mediate tumor cell proliferation, migration, invasion, metastasis, and angiogenesis; YR antagonists block the previous actions and promote the death of cancer cells. NPY favors tumor cell growth, migration, and metastasis and promotes angiogenesis in some tumors (e.g., breast cancer, colorectal cancer, neuroblastoma, pancreatic cancer), whereas in others it exerts an antitumor effect (e.g., cholangiocarcinoma, Ewing sarcoma, liver cancer). PYY or its fragments block tumor cell growth, migration, and invasion in breast, colorectal, esophageal, liver, pancreatic, and prostate cancer. Current data show the peptidergic system's high potential for cancer diagnosis, treatment, and support using Y2R/Y5R antagonists and NPY or PYY agonists as promising antitumor therapeutic strategies. Some important research lines to be developed in the future will also be suggested.

Peptide YY mediates inhibition of tumor growth and inflammation

Peptide YY (PYY) orchestrates the functions of the gut and the pancreas by regulating growth, digestion and absorption. In addition to its physiological role, PYY exhibits immune and antitrophic properties in the pancreas by decreasing cytokine and amylase release. Although the exact mechanism(s) of action are still incompletely understood, PYY interacts at the acinar level with numerous intracellular transcription factors. In addition to ameliorating pancreatic inflammation, novel synthetic analogs of PYY have been developed that are potent inhibitors of pancreatic cancer proliferation, in vitro and in vivo. Additionally, PYY and its analogs have been shown to inhibit the growth of breast, esophagus, and gastric cancer in vitro. We, herein, plan to review some of the methods employed in the laboratory while investigating the utility of PYY in the treatment of inflammation and cancer.

PYY and the pancreas: inhibition of tumor growth and inflammation

Peptide YY (PYY) orchestrates function of the gut and pancreas by regulating growth, digestion and absorption. In addition to its physiological role, PYY exhibits immune and antitrophic properties in the pancreas by decreasing cytokine and amylase release. Although the exact mechanism(s) of action are still not fully understood, PYY interacts at the acinar level with numerous intracellular transcription factors. In addition to ameliorating pancreatic inflammation, novel synthetic analogs of PYY have been developed that are potent inhibitors in the proliferation of pancreatic cancer. The present paper reviews our current findings with PYY and examines the therapeutic implications of its utility in treating inflammation and cancer.

Differential RNA expression profile by cDNA microarray in sporadic primary hyperparathyroidism (pHPT): primary parathyroid hyperplasia versus adenoma

BACKGROUND

Differential diagnosis between adenoma and hyperplasia in primary hyperparathyroidism (pHPT) remains a dilemma. The aim of this study was to assess differences in transcriptional genomic expression profiles between sporadic (nonfamilial) parathyroid hyperplasia (SPH), adenoma, and normal tissue.

METHODS

Parathyroid tissue from 12 patients with parathyroid adenoma, 3 with SPH, and 2 with normal glands was selected for analysis. Histopathology was reviewed in all cases, and all patients with adenomas presented normocalcemia for a minimum of 6 months after one gland resection. Hybridizations were performed in a microarray containing 19,968 human cDNA clones including contiguous replicates. Direct comparisons were performed with reverse labeling for every different pooled sample entity. Expression levels were analyzed using the SAM, SMA, LIMMA, Cluster, and PAM packages in the R environment for statistical computing.

RESULTS

There were significant statistical differences between SPH and adenomas. In the direct comparison, a total of 200 genes showed differential expression (P < 0.03): 61 genes were upregulated (> 1.65-fold increase) and 139 were downregulated (> 1.58-fold decrease) with a B value > 4.68 (99.08% probability of real differential expression). When SPH was compared to normal parathyroid tissue, 50 genes were differentially expressed: 42 were upregulated (> 1.89) and 8 were downregulated (> 1.7) with a B > 4.26 (98.6% probability of real differential expression). At least 17 genes were differentially expressed and able to discriminate SPH from adenoma or normal tissue. Upregulated genes were related to apoptosis inhibition, cell proliferation, transcriptional activity and cell adhesion, among other activities. Downregulated genes were mainly related to ion channel activity, lipopolysaccharides, prostaglandin-d synthase, and integral membrane proteins.

CONCLUSIONS

Our data suggest that SPH and adenoma have a singular molecular signature that, theoretically, could be used for the differential diagnosis of these entities and normal parathyroid tissue.

Inositol hexaphosphate (IP6): a novel treatment for pancreatic cancer

BACKGROUND

Inositol hexaphosphate (IP6) is a naturally occurring polyphosphorylated carbohydrate found in food sources high in fiber content. IP6 has been reported to have significant inhibitory effects against a variety of primary tumors including breast and colon. The effects of IP6 have not been evaluated in pancreatic cancer. We hypothesized that IP6 would significantly inhibit cell growth and increase the apoptotic rate of pancreatic cancer in vitro.

MATERIALS AND METHODS

Two pancreatic cancer cell lines (MIAPACA and PANC1) were cultured using standard techniques and treated with IP6 at doses of 0.5, 1.0, and 5.0 mm. Cell viability was measured by MTT at 24 and 72 h. Apoptosis was evaluated by Annexin V-FITC and results calculated using FACS analysis. Statistical analysis was performed by ANOVA.

RESULTS

Significant reductions (P < 0.01) in cellular proliferation were observed with all IP6 concentrations tested in both cell lines and at both time points. Reductions in cell proliferation ranged from 37.1 to 91.5%. IP6 increased early and late apoptotic activity (P < 0.01).

CONCLUSIONS

Treatment of pancreatic cancer with the common dietary polyphosphorylated carbohydrate IP6 significantly decreased cellular growth and increased apoptosis. Our findings suggest that IP6 has the potential to become an effective adjunct for pancreatic cancer treatment. Further in vivo and human studies are needed to evaluate safety and clinical utility of this agent in patients with pancreatic cancer.

In vitro effects of keyhole limpet hemocyanin in breast and pancreatic cancer in regards to cell growth, cytokine production, and apoptosis

BACKGROUND

We have previously shown the inhibitory effects of keyhole limpet hemocyanin (KLH) against breast and pancreatic cancer in vitro. We hypothesize that its actions in breast and pancreas cancer cells are via apoptotic or cytokine pathways.

METHODS

Two breast cancer cell lines, ZR75-1 and MCF-7, and one pancreas cancer cell line, PANC-1, were treated with KLH at 500 mug, 250 mug, and 250 ng/mL. Cell viability, cytokine production, and apoptosis were measured.

RESULTS

Significant growth inhibition was observed in all cell lines at all KLH concentrations tested. Significant changes in cytokine production were observed in all cell lines. An increase in early and late apoptotic activity was observed in the MCF-7, whereas a reduction in late apoptotic activity was observed in the ZR75-1 cells.

CONCLUSIONS

KLH directly inhibits the growth of human breast and pancreas cancer in vitro by apoptotic and nonapoptotic mechanisms.

Mitochondria Permeabilization by a Novel Polycation Peptide BTM-P1

Bacillus thuringiensis subsp. medellin is known to produce the Cry11Bb protein of 94 kDa, which is toxic for mosquito larvae due to permeabilization of the plasma membrane of midgut epithelial cells. Earlier we found that a 2.8-kDa novel peptide BTM-P1, which was artificially synthesized taking into account the primary structure of Cry11Bb endotoxin, is active against several species of bacteria. In this work we show that BTM-P1 induces cyclosporin A-insensitive swelling of rat liver mitochondria in various salt solutions but not in the sucrose medium. Inorganic phosphate and Ca(2+) significantly increased this effect of the peptide. The uncoupling action of BTM-P1 on oxidative phosphorylation was stronger in the potassium-containing media and correlated with a decrease of the inner membrane potential of mitochondria. In isotonic KNO(3), KCl, or NH(4)NO(3) media, a complete drop of the inner membrane potential was observed at 1-2 microg/ml of the peptide. The peptide-induced swelling was increased by energization of mitochondria in the potassium-containing media, but it was inhibited in the NaNO(3), NH(4)NO(3), and Tris-NO(3) media. All mitochondrial effects of the peptide were completely prevented by adding a single N-terminal tryptophan residue to the peptide sequence. We suggest a mechanism of membrane permeabilization that includes a transmembrane- and surface potential-dependent insertion of the polycation peptide into the lipid bilayer and its oligomerization leading to formation of ion channels and also to the mitochondrial permeability transition pore opening in a cyclosporin A-insensitive manner.

Peptide YY inhibits the growth of Barrett's esophageal adenocarcinoma in vitro

BACKGROUND

Peptide YY (PYY) is an endogenous gut hormone that inhibits the growth of certain cancers. Adenocarcinoma of the esophagus usually arises from Barrett's esophagus. We hypothesized that treatment of Barrett's adenocarcinoma with PYY would result in decreased proliferation.

METHODS

Barrett's cancer cell lines (BIC and SEG-1) were treated with PYY (3-36) at 500 pmol/mL. Viability was measured by MTT at 24 and 72 hours. Apoptosis and necrosis was evaluated by flow cytometry.

RESULTS

PYY reduced proliferation in SEG-1 cells at 24 hours (21.2% +/- 3.4%, P <0.001) and 72 hours (14.2% +/- 6.2%, P <0.001). In the BIC cells, growth was inhibited by 7.9% +/- 7.0%, P = 0.021 after 72 hours. PYY increased late apoptotic activity in SEG-1 cells by 31%, P = 0.014.

CONCLUSIONS

This is the first report of antiproliferative effects of PYY against Barrett's carcinoma in vitro. Reductions in cell growth appear to be mediated by proapoptotic mechanisms. Further investigation of PYY in the treatment of Barrett's adenocarcinoma is warranted.

Four peptides decrease the number of human pancreatic adenocarcinoma cells

BACKGROUND

Long-acting natriuretic peptide, vessel dilator, kaliuretic peptide and atrial natriuretic peptide are four peptide hormones synthesized by the same gene. Their main known biologic properties are sodium and water excretion and blood pressure lowering in both animals and humans.

METHODS AND MATERIALS

These four peptide hormones, each at their 1-microm concentrations, were evaluated for their ability to decrease the number and/or proliferation of human pancreatic adenocarcinoma cells in culture at 24, 48, 72 and 96 h.

RESULTS

Vessel dilator, long-acting natriuretic peptide, kaliuretic peptide and atrial natriuretic peptide decreased the number of human pancreatic adenocarcinoma cells in culture by 65% (P<0.001), 47% (P<0.01), 37% (P<0.05) and 34% (P<0.05), respectively, within 24 h. This decrease was sustained without any proliferation of the cancer cells occurring in the 3 days following this decrease in number. The mechanism of these peptide hormones' decrease in cancer cell number and antiproliferative effects was a 83% (P<0.001) or greater inhibition of DNA synthesis but not owing to enhanced apoptosis, i.e. programmed cell death. The two known mediators of these peptide hormones' mechanism(s) of action, i.e. cyclic GMP and prostaglandin E2, inhibited DNA synthesis in these adenocarcinoma cells by 51% and 23%, respectively.

CONCLUSIONS

Four peptide hormones significantly decrease the number of pancreatic adenocarcinoma cells within 24 h and inhibit the proliferation of these cells for at least 96 h. Their mechanism of doing so is via inhibition of DNA synthesis mediated in part by cyclic GMP.

Role of gastrointestinal hormones in the proliferation of normal and neoplastic tissues

Gastrointestinal (GI) hormones are chemical messengers that regulate the physiological functions of the intestine and pancreas, including secretion, motility, absorption, and digestion. In addition to these well-defined physiological effects, GI hormones can stimulate proliferation of the nonneoplastic intestinal mucosa and pancreas. Furthermore, in an analogous fashion to breast and prostate cancer, certain GI cancers possess receptors for GI hormones; growth can be altered by administration of these hormones or by blocking their respective receptors. The GI hormones that affect proliferation, either stimulatory or inhibitory, include gastrin, cholecystokinin, gastrin-releasing peptide, neurotensin, peptide YY, glucagon-like peptide-2, and somatostatin. The effects of these peptides on normal and neoplastic GI tissues will be described. Also, future perspectives and potential therapeutic implications will be discussed.

In vitro anticancer effects of a novel immunostimulant: keyhole limpet hemocyanin

BACKGROUND

Keyhole limpet hemocyanin (KLH) is a recently described immune stimulant and hapten carrier derived from a circulating glycoprotein of the marine mollusk Megathura crenulata. It has been reported to be a potent form of intravesical immunotherapy for the treatment of transitional cell carcinoma of the bladder and has been used in a variety of genitourinary tumors. We hypothesized that KLH would be effective against other cancer cells in vitro.

METHODS

Multiple cancer cell lines were tested, including estrogen-dependent breast (MCF-7), estrogen-independent breast (ZR75-1), pancreas (PANC-1, MIA-PaCa), and prostate (DU145). Serial twofold dilutions of KLH were prepared in sterile 96-well plates. Dose-response curves were performed beginning with a concentration of 100 microg of KLH/well and ending at a concentration of 0.8 ng/well. Cells were added at concentrations of 5 x 10(4) cells per well. Cell viability was evaluated at 24 and 72 h by MTT assay at an absorbance of 570 nm.

RESULTS

Significant (P < 0.05) cancer cell growth inhibition was observed in four of the five cell lines tested at both time treatment intervals. The breast cancer line ZR75-1 exhibited a mean growth inhibition of 43 +/- 1.1% (range 37 to 59%) at 72 h, whereas treated MCF-7 cells had an average of 39 +/- 9.1% growth inhibition (range 35 to 44%) at these same concentrations. Treated PANC-1 cells had a mean growth inhibition of 19 +/- 0.8% (range 4 to 46%) at 72 h. The DU145 prostate cancer cell line averaged a 6 +/- 1.3% growth inhibition (range -19 to 55%) over the concentrations tested.

CONCLUSIONS

The direct growth inhibition of multiple tumor cell-lines exhibited by KLH is significant and warrants further in vitro mechanistic studies and in vivo experiments. Investigation into the efficacy and mechanism of response could directly lead to more effective treatment regimens for patients suffering from these diseases.

Peptide YY and cancer: current findings and potential clinical applications

Peptide YY (PYY) is a naturally occurring gut hormone with mostly inhibitory actions on multiple tissue targets. PYY has been identified in several carcinoid tumors and a decreased expression of PYY may be relevant to the development and progression of colon adenocarcinoma. Treatment with PYY decreases growth in pancreatic and breast tumors, most likely through a reduction in intracellular cAMP. In cancer patients, PYY may also improve malnutrition that results from iatrogenic causes or cachexia associated with advanced disease. PYY plays a significant role in multiple aspects of cancer from regulation of cell growth to potential therapeutic applications.

B-cell leukemia protein-2 and peptide YY chemotherapy resistance in colon cancer

BACKGROUND

Inhibition of apoptosis may allow cells with drug-induced damage to escape programmed cell death. The bcl-2 protein inhibits apoptosis and bcl-2 overexpression has been associated with drug resistance. It is our hypothesis that higher levels of bcl-2 expression will be seen in colon cancer cells resistant to PYY treatment.

METHODS

Caco2 and HCT116 colon cancer cells were treated with 2 microM PYY for 24 hours. Protein was extracted from cells surviving PYY treatment; bcl-2 expression was measured by enzyme-linked immunosorbent assay (ELISA) and confirmed by Western blotting.

RESULTS

Caco2 and HCT116 cells surviving PYY treatment demonstrated increased bcl-2 from 20.54+/-2.7 to 28.63+/-2.20 units/mL (P <0.05) and 21.98+/-1.28 to 29.32*+/-2.26 units/mL, respectively.

CONCLUSIONS

Increased expression of bcl-2 is seen in a population of colon cancer cells resistant to PYY. Hence, bcl-2 may protect neoplastic cells from apoptosis; its levels may be useful in predicting chemotherapy response and in selecting appropriate drug regimens.

Peptide YY inhibits growth of human breast cancer in vitro and in vivo

BACKGROUND

Hormonal manipulation is important in the treatment of breast cancer. Gastrointestinal hormones may have antiproliferative effects on malignancies arising outside the gastrointestinal tract. Peptide YY (PYY) suppresses growth of, and levels of, intracellular cyclic adenosine monophosphate (cAMP) in pancreatic adenocarcinoma. We hypothesized that PYY would inhibit growth of breast cancer.

MATERIALS AND METHODS

MCF-7 human breast infiltrative ductal carcinoma cells in 96-well plates were treated with PYY at 1.25 pmol/mcl. Control wells received an equal volume of bovine serum albumin to mimic experimental conditions. In vitro survival was determined by MTT assays, which reflect cell viability by measuring mitochondrial NADH-dependent dehydrogenase activity. MCF-7 cells in six-well plates were treated with PYY or albumin as described above. Intracellular cAMP levels in cell lysates were determined with a tritiated cAMP assay. One million MCF-7 cells were injected into mammary fat pads of 20 female athymic nude mice. Pellets releasing PYY at 400 pmol/kg/h were placed subcutaneously in 10 mice 24 h prior to cell inoculation. Tumors were harvested after 21 days, weighed, and measured with vernier calipers.

RESULTS

PYY reduced in vitro growth by 40% (P < 0.001). Intracellular cAMP levels in PYY-treated cells were 62.4% less than those of controls (P < 0.001). Tumors from control mice weighed twice as much as those from PYY-treated mice (P < 0.006); volume of PYY-exposed tumors was one-third that of controls (P < 0.005).

CONCLUSIONS

PYY inhibits growth of breast cancer in vitro and in vivo and may be of benefit in the treatment of this malignancy. The reduction in intracellular cAMP levels may contribute to the observed suppression of cell proliferation.