Combination chemotherapy with 5-fluorouracil (5FU) and 1,3-bis(2-chloro-ethyl)-1-nitrosourea (BCNU) prolongs survival of rats with dimethylhydrazine-induced colon cancer

Morin supplementation modulates PERK branch of UPR and mitigates 1,2-dimethylhydrazine-induced angiogenesis and oxidative stress in the colon of experimental rats

Angiogenesis, disturbance in redox homeostasis, and deregulated redox signaling are considered as common hallmarks of cancer progression and chemo resistance. In this context, PERK (protein kinase PKR-like ER kinase) branch of the unfolded protein response (UPR), an adaptive mechanism triggered by endoplasmic reticulum (ER) stress to cope with protein misfolding and perturbed proteostasis, has shown to regulate angiogenesis and oxidative stress. This study aimed to investigate the impact of morin, a poly phenolic compound from the family of Moraceae on PERK-Nrf2-VEGF axis in experimental rats challenged with the colon specific procarcinogen 1,2-dimethylhydrazine (DMH). Male albino Wistar rats were randomized into four groups (n = 6) viz., control, morin control, DMH control, and DMH administered rats treated with morin. Immunohistochemical analysis of colonic cross-section revealed that DMH alone administered rats showed significantly increased expression of Nrf2 predominantly in the cytoplasm. Angiogenic growth factors viz., VEGF, PDGF, and bFGF are also shown to be increased in the DMH alone administered tumor bearing rats as compared to control. Significant downregulation was also observed in the downstream targets of Nrf2 such as hemeoxygenase 1 (HO1), glutathione peroxidase 2 (GPX2), thioredoxin (TRXN), glutathione S transferase (GST), and uridine glucuronyl transferase (UGT) as evidenced by the qPCR analysis. Immunoblot analysis revealed that onset of oxidative stress and angiogenesis in the colon of DMH alone administered rats were due to downregulation of pPERK along with its downstream targets such as peIF2α and CHOP. Supplementation of morin reversed the DMH-induced alterations and suppresses oxidative stress and angiogenesis via PERK phosphorylation.

Antiproliferative effect of p-Coumaric acid targets UPR activation by downregulating Grp78 in colon cancer

p-CA is a naturally occurring phenolic acid present in most plants and in all commonly consumed vegetables and fruits. Here we demonstrated the anti-cancer effect of the food borne phytochemical p-CA both in vitro and in vivo models of colon cancer using growth rate and tumor incidence as endpoints. Glucose regulated protein (GRP78) induction and UPR activation plays a key role in oncogenic progression, therefore increased dependence of cancer cells on these UPR signaling pathways for survival can be exploited for anti-cancer research. Hence we investigated the effect of p-CA on Grp78 a molecular chaperone often upregulated in colon cancer and its impact on unfolded protein response (UPR). Administration of the procarcinogen 1,2- dimethylhydrazine (DMH) causes Grp78 upregulation and tumor adaptation via UPR activation. The adaptive activity of UPR activates antiapoptotic NF-κB that results in upregulation of the markers of inflammation and angiogenesis. Supplementation of p-CA downregulated Grp78 and activated UPR mediated apoptosis both in in vitro and in vivo models of colon cancer. Further we observed that p-CA significantly reduced inflammation by decreasing the expression of cytokines COX-2, IL-6, TNF-α and PGE2 as analyzed by q-PCR and also reduced the expression of p-p65 and p-IκBα as analyzed by western blot. Further mechanistic insights revealed that p-CA inhibits Grp78 upregulation in cancer cells through activation of PERK-eIF2α-ATF-4-CHOP pathway that culminates in apoptosis inducing effect of p-CA.

Effect of oral Lactococcus lactis containing endostatin on 1, 2-dimethylhydrazine-induced colon tumor in rats

AIM

To investigate the effects of oral Lactococcus lactis (L lactis) containing endostatin on 1, 2-dimethylhydrazine (DMH)-induced rat colorectal cancer.

METHODS

Recombinant endostatin was produced by the expression of L lactis NZ9000. Sixty male Wistar rats were injected with DMH (40 mg/kg body weight) subcutaneously once a week for 10 wk to induce colorectal cancer. The rats were gavaged with 1 mL of endostatin at a dose of 1 x 10(8)/d and fed with the basal diet. The animals were killed after 22 wk for histopathological examination. The total time of experimental observation was 58 wk.

RESULTS

Rat endostatin protein was expressed in L lactis. Recombinant endostatin exhibited a significant effect on colorectal cancer (P<0.05). Furthermore, the mean survival time of the rats treated with endostatin was longer than that of the animals treated with DMH. There was no statistically significant difference between the rats treated with endostatin and those treated with DMH. The results showed that endostatin could not result in complete cure.

Crystal structure and conformation of 5-fluorouridine: conformational preferences for 5-fluorinated pyranosides

Crystals of 5-fluorouridine (5FUrd) have unit cell dimensions a = 7.716(1), b = 5.861(2), c = 13.041(1)A, alpha = gamma = 90 degrees, beta = 96.70 degrees (1), space group P2(1), Z = 2, rho obs = 1.56 gm/c.c and rho calc = 1574 gm/c.c The crystal structure was determined with diffractometric data and refined to a final reliability index of 0.042 for the observed 2205 reflections (I > or = 3sigma). The nucleoside has the anti conformation [chi = 53.1(4) degrees] with the furanose ring in the favorite C2'-endo conformation. The conformation across the sugar exocyclic bond is g+, with values of 49.1(4) and -69.3(4) degrees for phi(theta c) and phi (infinity) respectively. The pseudorotational amplitude tau(m) is 34.5 (2) with a phase angle of 171.6(4) degrees. The crystal structure is stabilized by a network of N-H...O and O-H...O involving the N3 of the uracil base and the sugar 03' and 02' as donors and the 02 and 04 of the uracil base and 03' oxygen as acceptors respectively. Fluorine is neither involved in the hydrogen bonding nor in the stacking interactions. Our studies of several 5-fluorinated nucleosides show the following preferred conformational features: 1) the most favored anti conformation for the nucleoside [chi varies from -20 to + 60 degrees] 2) an inverse correlation between the glycosyl bond distance and the chi angle 3) a wide variation of conformations of the sugar ranging froni C2'-endo through C3'-endo to C4'-exo 4) the preferred g+ across the exocyclic C4'-C5' bond and 5) no role for the fluorine atom in the hydrogen bonding or base stacking interactions.

Lack of inhibitory effects of Lactic acid bacteria on 1,2-dimethylhydrazine-induced colon tumors in rats

AIM: A myriad of healthful effects has been attributed to the probiotic lactic acid bacteria, perhaps the most controversial issue remains that of anticancer activity. This study was aimed at investigating the putative anti-cancer effects of lactic acid bacteria strains on the progression of colon tumor in 1,2-dimethylhydrazine (DMH)-treated animals.

METHODS: The strain of lactic acid bacteria used in this study was lactic acid bacteria NZ9000 that conformed to the characteristics of plasmid free. Sixty male Wistar rats were given subcutaneous injections of DMH at a dose of 40 mg/kg body wt or saline once a week for 10 wk. The rats were divided into 6 experimental groups. After the last DMH injection, animals in groups 1 and 4 were gavaged with 1 mL of lactic acid bacteria at a dose of 5 × 10⁹ per day or vehicle until sacrifice at the end of week 22 or week 52. Animals in groups 1-3 were killed at the end of week 22 for histopathological examination. The whole period of experimental observation was 52 wk.

RESULTS: By the end of 22nd week, final average body weights of the rats treated with DMH alone and all animals receiving lactic acid bacteria were significantly decreased compared with the vehicle control (P < 0.05). No differences in tumor incidence, multiplicity, dimensions and stage in the colonic mucosa were observed among the groups. At week 52, the survival rate of the rats administered lactic acid bacteria was lower than that of the rats treated with DMH that were fed on control fluids of non-lactococcus lactis. The mean survival time of lactic acid bacteria-treated animals was 39 wk.

CONCLUSION: These results indicate that lactic acid bacteria lacks inhibitory effects on the progression of colon tumor in DMH-treated animals, and does not support the hypothesis that alteration of colonic flora may exert an influence on the progression of colon tumor.

Experimental colorectal cancer as a model of human disease

Colorectal cancer may now be induced consistently in experimental animals by the carcinogen 1,2-dimethylhydrazine (DMH). Adenomas and adenocarcinomas are produced in the large bowel and these resemble human colorectal cancer both macroscopically, and in their clinical behaviour. They are a close model of human disease and may be used for the evaluation of anti-cancer therapies and for the development of a diagnostic test for colorectal cancer.

Growth characteristics of autochthonous experimental colonic tumors as assessed by serial colonoscopic measurement in rats

We report the growth characteristics of autochthonous experimental colonic tumors as assessed by serial measurements at colonoscopy. Male Fischer 344 rats were given 10 weekly subcutaneous injections of the bowel carcinogen azoxymethane, 10 mg/kg (weeks 1-10). Beginning in week 15, colonoscopy to the splenic flexure was performed weekly with a pediatric fiberoptic bronchoscope. Width of identified tumors was measured in photographs that included a scale passed through the biopsy channel, and tumor volume was calculated using computerized image analysis. Sensitivity, specificity, predictive values, and efficiency of colonoscopy for identification of tumors were 85%-100%. Cumulative tumor incidence in the descending colon increased in a relatively linear fashion from 3% at week 15 to 68% at week 30. Tumor width by colonoscopy correlated well with width at necropsy (r = 0.951). Growth curves of individual tumors were highly variable; however, tumor width showed stable mean weekly growth rates. By contrast, mean calculated tumor volume rose exponentially, with deviation from the fitted curve in the sixth week. All tumors greater than 3 mm in width or greater than 10 mm3 in volume showed invasion. Final tumor width and volume, and growth of tumor volume during the initial week but not the later weeks of observation, correlated with depth of invasion. Our findings suggest that colonoscopic measurement was useful to study the growth characteristics of autochthonous experimental colonic tumors; azoxymethane administration produced persistently altered colonic epithelium that had variable latent periods until development of visible tumors in individual rats; the growth curves of individual colonic tumors were exponential, although variable, during the initial weeks; invasion was found in small tumors and depth of invasion correlated with growth rate during the initial week but not the later weeks. This aggressive behavior of the tumors early in their course contrasts with colorectal adenomas in humans and argues against the routine occurrence of an adenoma-carcinoma sequence in the model we used.