Abstract 4580: Primary tumor-induced immunity eradicates disseminated tumor cells in syngeneic mouse model

Although clinically apparent metastasis is associated with late stages of cancer development, micro-metastatic dissemination may be an early event. However, the fate of these early disseminated tumor cells (DTC) remains elusive.

Using the syngeneic mouse models, we demonstrated that although both orthotopically-implanted murine 4T1 and EMT6 tumors are capable of disseminating into secondary organs, only 4T1 tumors develop overt metastasis. However, EMT6 tumors induce an anti-tumor immunity in syngeneic mice and that eradicates disseminated tumor cells (DTC) in distant organs. Following the complete removal of primary EMT6 tumors, mice do not develop detectable metastasis and generate an immunological memory that leads to complete elimination of repeatedly injected tumor cells via tail vein. Conversely, these cells readily grow and metastasize in immuno-deficient athymic or Rag2- mice, and when g-MDSCs from 4T1 tumor-bearing mice were co-injected into immunocompetent EMT6 primed mice. In contrast to complete resection, mice with residual tumors following surgery exhibited an enhanced growth of local and concomitant growth of DTCs at metastatic site with increased g-MDSCs accumulation in lung and spleen.

Together, our results suggest that some tumors are capable of inducing anti-tumor immunity against the DTCs when complete resection of primary tumor cures animals. However, in the presence of residual tumors, inflammation induced by surgical procedure promote the growth of DTCs.

Citation Format: Raziye Piranlioglu, Eunmi Lee, Maria Ouzuonova, Riley Rodier, Adam Greer, Feyzanur Bayraktar, Omer Can Durmus, Ali S. Arbab, Muthushamy Thangaraju, Max S. Wicha, Esteban Celis, Hasan Korkaya. Primary tumor-induced immunity eradicates disseminated tumor cells in syngeneic mouse model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4580.

Primary tumor-induced immunity eradicates disseminated tumor cells in syngeneic mouse model

Although clinically apparent metastasis is associated with late stages of cancer development, micro-metastatic dissemination may be an early event. However, the fate of these early disseminated tumor cells (DTC) remains elusive. We show that despite their capacity to disseminate into secondary organs, 4T1 tumor models develop overt metastasis while EMT6-tumor bearing mice clear DTCs shed from primary tumors as well as those introduced by intravenous (IV) injection. Following the surgical resection of primary EMT6 tumors, mice do not develop detectable metastasis and reject IV-injected tumor cells. In contrast, these cells readily grow and metastasize in immuno-deficient athymic or Rag2^−/− mice, an effect mimicked by CD8⁺ T-cell depletion in immunocompetent mice. Furthermore, recombinant G-CSF or adoptive transfer of granulocytic-MDSCs isolated from 4T1 tumor-bearing mice, induce metastasis by suppressing CD8⁺ T-cells in EMT6-primed mice. Our studies support the concept of immune surveillance providing molecular insights into the immune mechanisms during tumor progression.

Dissemination of tumor cells from the primary site is an early event. Here, the authors show that the early disseminated tumor cells are actively cleared by the host cytotoxic T lymphocytes induced by the primary tumor and that infiltration of granulocytic myeloid-derived suppressor cells counteracts such immune protection and allow metastasis development.

Abstract P5-07-12: RAD51AP1 is a novel prognostic marker and therapeutic target for breast cancer

Background: Ionizing radiation is one of the most effective therapeutic strategies for the treatment of breast cancer and is considered as a more appropriate therapy for patients with high-risk of recurrence. Despite substantial benefits are achievable with this treatment, especially for ductal carcinoma and early invasive cancer, the critical barrier in using this treatment strategy is that tumor cells develop radioresistance, which in turn progress into advanced invasive cancer. Breast cancer stem cells (BCSCs), a subpopulation of cells within the tumor with a characteristic feature of self-renewal, play a critical role radioresistance and treatment failure. BCSCs exhibit increased DNA repair activity by increasing RAD51AP1 for their prolonged survival and to evade from the radiation therapy. We explored the expression profile of RAD51AP1 in BCSCs, human normal and various subtypes of breast tumor tissues and cell lines and response to chemo- and radiation- therapy.

Methods: Gene expression (RNA and protein) profile was assessed using semi-quantitative and real-time PCR (qPCR) and western blot analyses. RAD51AP1 expression and its prognostic value in large cohort of human samples were analyzed by TCGA, GOBO, and Kaplan-Meier plotter integrative bioinformatics interface analyses. Breast cancer stem cell (BCSC) status was analyzed by FACS using CD24 and CD49f cell surface marker. Cell death was analyzed by propidium iodide (PI) stained cell cycle analysis.

Results: We found that tumor propagating CD49f+CD24+ cells activate RAD51AP1 more promptly than non-tumorigenic CD49f-CD24- cells and confer chemo- and radiation- therapy resistance. RAD51AP1 inactivation facilitates chemo- and radiation- therapy response by depleting CD49f+CD24+ cells with significant activation of apoptotic cell death signaling. RAD51AP1 expression was significantly higher in BC, especially in the basal triple-negative and HER2-positive BC subtype, than in normal mammary tissue. Further, RAD51AP1 expression is highest in grade III histological tumor types and negatively associated to overall disease-free survival. RAD51AP1 levels across different BC cell lines showed that triple-negative breast cancer (TNBC) cell lines expressed highest level of this gene than other sub types.

Conclusion:Overall, our findings provide evidence that BCSCs utilize DNA repair signaling for their self-renewal and RAD51AP1 play a critical role in BCSC self-renewal and maintenance. Further, RAD51AP1 expression profile can be used as a prognostic marker to monitor disease progression and chemotherapy response.

Citation Format: Thangaraju M, Kolhe RB, Pathania R. RAD51AP1 is a novel prognostic marker and therapeutic target for breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P5-07-12.

Abstract B50: MEK inhibitors mount a two-pronged attack to kill estrogen receptor positive (ER+) breast cancer cells undergoing hormonal therapy: Attenuated autophagy and induction of apoptosis

In a recent study, we identified the dephosphorylated form of BimEL as a key death effector of antiestrogen treatment of ER+ breast cancer cells and further showed that MEK1/MAPK1/2 blockade was required to produce high levels of dephosphorylated BimEL, particularly under conditions of insulin like growth factor 1 (IGF1) stimulation (Periyasamy-Thandavan et al., Breast Cancer Res. 14, 2012). Studies by others have identified MEK1/MAPK1/2 activation as essential to autophagy, a catabolic process induced by multiple stresses including ROS, ceramide accumulation, and nutrient deprivation. Autophagy induction results in autophagosome formation, trafficking of damaged proteins and mitochondria to the autophagosomes, and ultimately fusion with the lysosomes resulting in autolysosome formation. The autolysosome and its contents are degraded by the hydrolytic enzymes of the lysosome. Of particular interest to antiestrogen treatment of breast cancer, we and others have shown that pro-survival autophagy facilitates the emergence of antiestrogen resistant breast cancer cells. Thus, we are keenly interested in how MEK1/MAPK1/2 signaling affects pro-survival autophagy and if MEK blockade would be an effective approach toward blocking pro-survival autophagy in ER+ breast cancer cells undergoing hormonal treatment. In this study, we hypothesized that the requirement of MEK1/MAPK1/2 for pro-survival autophagy is due, in part, to its role in blocking the intracellular accumulation of dephosphorylated BimEL. To test this hypothesis, we modulated the expression of dephosphorylated BimEL with either a BimEL cDNA expression vector, siRNA targeting of BimEL, or MEK1 blockade with the small molecule inhibitor U0126 and determined the levels of the autophagic flux in ER+ breast cancer cells undergoing antiestrogen treatment. The determination of autophagic flux was made by comparing the levels of two proteins involved in autophagy -the LC3 /Atg8 and p62 (SQSTM1) proteins- in cell populations undergoing the different treatments in the presence or absence of chloroquine (CQ). The lipidated form of LC3, designated LC3II, is typically increased in cells undergoing autophagy, facilitates the formation of the mature autophagosomal membranes, and is subsequently degraded in the autolysosome. The p62 protein is required for the delivery of ubiquitinated protein complexes to the autophagosome and is degraded along with the ubiquitinated complex of proteins. CQ is a lysosomotrophic agent routinely used in autophagic flux assays because it blocks the turnover of autolysosomes with accumulation of LC3 II and p62, allowing the total levels of LC3II and p62 to be ascertained under all treatment conditions. These studies showed that siRNA targeting of BimEL increased basal and tamoxifen-induced autophagy in ER+ MCF-7 breast cancer cells. In contrast, the overexpression of dephosphorylated BimEL led to an increase in LC3 II and p62 levels due to a significant attenuation of autophagic flux (approximately 50%) in antiestrogen-treated cell populations. Current studies are focused on the mechanism of BimEL-mediated blockade of pro-survival autophagy, with the long term goal of optimizing this “downstream effector” function of MEK1/MAPK1/2 blockade in ER+ breast cancer cells for improved therapeutic outcome.

Citation Format: S. Takhar, M. Manning, A. Eason, M. Dix, S. Periyasamy-Thandavan, R. Padi, E. Bieberich, W. Hill, D. Browning, V. Ganapathy, M. Thangaraju, P. V. Schoenlein. MEK inhibitors mount a two-pronged attack to kill estrogen receptor positive (ER+) breast cancer cells undergoing hormonal therapy: Attenuated autophagy and induction of apoptosis. [abstract]. In: Proceedings of the AACR Special Conference on RAS Oncogenes: From Biology to Therapy; Feb 24-27, 2014; Lake Buena Vista, FL. Philadelphia (PA): AACR; Mol Cancer Res 2014;12(12 Suppl):Abstract nr B50. doi: 10.1158/1557-3125.RASONC14-B50

Role of SLC5A8, a plasma membrane transporter and a tumor suppressor, in the antitumor activity of dichloroacetate

There has been growing interest among the public and scientists in dichloroacetate as a potential anticancer drug. Credible evidence exists for the antitumor activity of this compound, but high concentrations are needed for significant therapeutic effect. Unfortunately, these high concentrations produce detrimental side effects involving nervous system, thereby precluding its use for cancer treatment. The mechanistic basis of the compound’s antitumor activity is its ability to activate pyruvate dehydrogenase complex through inhibition of pyruvate dehydrogenase kinase. Since the compound inhibits the kinase at micromolar concentrations, it is not known why therapeutically prohibitive high doses are needed for suppression of tumor growth. We hypothesized that lack of effective mechanisms for the entry of dichloroacetate into tumor cells may underlie this phenomenon. Here we show that SLC5A8 transports dichloroacetate very effectively with high affinity. This transporter is expressed in normal cells, but the expression is silenced in tumor cells via epigenetic mechanisms. The lack of the transporter makes tumor cells resistant to the antitumor activity of dichloroacetate. However, if the transporter is expressed in tumor cells ectopically, the cells become sensitive to the drug at low concentrations. This is evident in breast cancer cells, colon cancer cells, and prostate cancer cells. Normal cells, which constitutively express the transporter, are however not affected by the compound, indicating the tumor cell-selective therapeutic activity. The mechanism of the antitumor activity of the compound is still its ability to inhibit pyruvate dehydrogenase kinase and force mitochondrial oxidation of pyruvate. Since the silencing of SLC5A8 in tumors involves DNA methylation and its expression can be induced by treatment with DNA methylation inhibitors, our findings suggest that combining dichloroacetate with a DNA methylation inhibitor would offer a means to reduce the doses of dichloroacetate to avoid detrimental effects associated with high doses but without compromising antitumor activity.

Assessing the Zinc solubilization ability of Gluconacetobacter diazotrophicus in maize rhizosphere using labelled (65)Zn compounds

Solubilization of insoluble zinc compounds like ZnCO(3) and ZnO by G. diazotrophicus was confirmed using radiotracers. The zinc compounds (ZnCO(3) and ZnO) were tagged with (65)Zn. (65)ZnCO(3) and (65)ZnO was effectively solubilized and the uptake of zn by the plants also more in G. diazotrophicus inoculated treatments compared to the uninoculated treatments. Three types of soils (Zn deficientsterile, Zn deficient-unsterile, and Zn sufficient-sterile) were used in experiment. Among the three soils, Zn deficient-unsterile soil registered maximum zinc solubilization compared to other two soils. This may be due to other soil microorganisms in unsterile soil. Application of ZnO with G. diazotrophicus showed better uptake of the nutrient.

PKG inhibits TCF signaling in colon cancer cells by blocking beta-catenin expression and activating FOXO4

Activation of cGMP-dependent protein kinase (PKG) has anti-tumor effects in colon cancer cells but the mechanisms are not fully understood. This study has examined the regulation of beta-catenin/TCF signaling, as this pathway has been highlighted as central to the anti-tumor effects of PKG. We show that PKG activation in SW620 cells results in reduced beta-catenin expression and a dramatic inhibition of TCF-dependent transcription. PKG did not affect protein stability, nor did it increase phosphorylation of the amino-terminal Ser33/37/Thr41 residues that are known to target beta-catenin for degradation. However, we found that PKG potently inhibited transcription from a luciferase reporter driven by the human CTNNB1 promoter, and this corresponded to reduced beta-catenin mRNA levels. Although PKG was able to inhibit transcription from both the CTNNB1 and TCF reporters, the effect on protein levels was less consistent. Ectopic PKG had a marginal effect on beta-catenin protein levels in SW480 and HCT116 but was able to inhibit TCF-reporter activity by over 80%. Investigation of alternative mechanisms revealed that cJun-N-terminal kinase (JNK) activation was required for the PKG-dependent regulation of TCF activity. PKG activation caused beta-catenin to bind to FOXO4 in colon cancer cells, and this required JNK. Activation of PKG was also found to increase the nuclear content of FOXO4 and increase the expression of the FOXO target genes MnSOD and catalase. FOXO4 activation was required for the inhibition of TCF activity as FOXO4-specific short-interfering RNA completely blocked the inhibitory effect of PKG. These data illustrate a dual-inhibitory effect of PKG on TCF activity in colon cancer cells that involves reduced expression of beta-catenin at the transcriptional level, and also beta-catenin sequestration by FOXO4 activation.

Ecological occurrence of Gluconacetobacter diazotrophicus and nitrogen-fixing Acetobacteraceae members: their possible role in plant growth promotion

Gluconacetobacter diazotrophicus has a long-standing history of bacterial-plant interrelationship as a symbiotic endophyte capable of fixing atmospheric nitrogen. In low nitrogen fertilized sugarcane fields it plays a significant role and its occurrence was realised in most of the sugarcane growing countries. In this mini review, the association of G. diazotrophicus with sugarcane, other crop plants and with various hosts is discussed. The factors affecting survival in the rhizosphere and the putative soil mode of transmission are emphasized. In addition, other N(2)-fixing Acetobacteraceae members, including Gluconacetobacter azotocaptans, Gluconacetobacter johannae and Swaminathania salitolerans, occurring in coffee, corn and rice plants are also covered. Lastly, the plant-growth-promoting traits identified in this group of bacteria, including N(2) fixation, phytohormone synthesis, P and Zn solubilization and biocontrol, are analysed.

Method and quantity of liquid formulation of phosphobacteria required for seed inoculation

The survival of vegetative and sporulated cells of the Bacillus cultures on the seeds of the crop plants was tried in different combinations. One milliliter inoculum with 1 mL adhesive combination or sterile water showed better results followed by 1.5 mL inoculum with 0.5 mL adhesive or sterile water. The population of 5.5x10(5) cfu seed(-1) on black gram, 10.5x10(5) cfu seed(-1) on soybean and 6.5x10(5) cfu seed(-1) on maize were observed after 12 h of incubation in 1 mL sporulated inoculum mixed with 1 mL of rice gruel. The sporulated inoculum along with rice gruel favoured the adherence of the regenerated cells as rice gruel is rich in nutrient content.

Sporulation and regeneration efficiency of phosphobacteria (Bacillus megaterium var phosphaticum)

Sporulation in Bacillus megaterium var phosphaticum (PB - 1) was induced using modified nutrient media. This modified medium induced sporulation within 36 h. After spore induction the spores were kept under refrigerated (5°C) and room temperature (32°C) for five months and survival of spores was studied at 15 days intervals by plating them in nutrient agar medium. It was observed that there was not much variation in the storage temperature (5°C & 32°C). The spore cells of Bacillus megaterium var phosphaticum (PB - 1) were observed up to five months of storage under refrigerated (5°C) and room temperature (32°C). Regeneration of spore cells into vegetative cells was studied in tap water, rice gruel, nutrient broth, sterile lignite and sterile water at different concentrations of spore inoculum. The multiplication of sporulated Bacillus megaterium var phosphaticum culture was fast and reached its maximum (29.5 × 10(8) cfu ml(-1)) in nutrient broth containing 5 per cent inoculum level.

Solubilization of insoluble zinc compounds by Gluconacetobacter diazotrophicus and the detrimental action of zinc ion (Zn2+) and zinc chelates on root knot nematode Meloidogyne incognita

AIM

To examine the zinc (Zn) solubilization potential and nematicidal properties of Gluconacetobacter diazotrophicus.

METHODS AND RESULTS

Atomic Absorption Spectrophotometer, Differential Pulse Polarography and Gas Chromatography Coupled Mass Spectrometry were used to estimate the total Zn and Zn(2+) ions and identify the organic acids present in the culture supernatants. The effect of culture filtrate of Zn-amended G. diazotrophicus PAl5 on Meloidogyne incognita in tomato was examined under gnotobiotic conditions. Gluconacetobacter diazotrophicus PAl5 effectively solubilized the Zn compounds tested and 5-ketogluconic acid was identified as the major organic acid aiding the solubilization of zinc oxide. The presence of Zn compounds in the culture filtrates of G. diazotrophicus enhanced the mortality and reduced the root penetration of M. incognita under in vitro conditions.

CONCLUSIONS

5-ketogluconic acid produced by G. diazotrophicus mediated the solubilization process and the available Zn(2+) ions enhanced the nematicidal activity of G. diazotrophicus against M. incognita.

SIGNIFICANCE AND IMPACT OF THE STUDY

Zn solubilization and enhanced nematicidal activity of Zn-amended G. diazotrophicus provides the possibility of exploiting it as a plant growth promoting bacteria.

Solubilization of zinc compounds by the diazotrophic, plant growth promoting bacterium Gluconacetobacter diazotrophicus

Gluconacetobacter diazotrophicus an endophytic diazotroph also encountered as rhizosphere bacterium is reported to possess different plant growth promoting characteristics. In this study, we assessed the zinc solubilizing potential of G. diazotrophicus under in vitro conditions with different Zn compounds using glucose or sucrose as carbon sources. G. diazotrophicus showed variations in their solubilization potential with the strains used and the Zn compounds tested. G. diazotrophicus PAl5 efficiently solubilized the Zn compounds tested and ZnO was effectively solubilized than ZnCO(3) or Zn(3)(PO(4))(2). The soluble Zn concentration was determined in the culture supernatant through Atomic Absorption Spectrophotometer. Gas chromatography coupled Mass Spectrometry analysis revealed 5-ketogluconic acid, a derivative of gluconic acid as the major organic acid produced by G. diazotrophicus PAl5 cultured with glucose as carbon source. This organic anion may be an important agent that helped in the solubilization of insoluble Zn compounds.

Induction of the BRCA2 promoter by nuclear factor-kappa B

BRCA2 is a tumor suppressor gene that has been implicated in response to DNA damage, cell cycle control, and transcription. BRCA2 has been found to be overexpressed in many breast tumors, suggesting that altered expression of the BRCA2 gene may contribute to breast tumorigenesis. To determine how BRCA2 is overexpressed in tumors, we investigated the transcriptional regulation of the BRCA2 promoter. Deletion mapping of the BRCA2 promoter identified three regions associated with 3-fold activation or repression and one upstream stimulatory factor binding site associated with 20-fold activation. Gel shift and cotransfection studies verified the role of USF in regulation of BRCA2 transcription. Analysis of the -144 to -59 region associated with 3-fold activation identified a putative NFkappaB binding site. Cotransfection of the p65 and p50 subunits of NFkappaB up-regulated the BRCA2 promoter 16-fold in a luciferase reporter assay, whereas mutations in the binding site ablated the effect. Gel shift and supershift assays with anti-p65 and -p50 antibodies demonstrated that NFkappaB binds specifically to the NFkappaB site. In addition, ectopic expression of NFkappaB resulted in increased levels of endogeneous BRCA2 expression. Thus, NFkappaB and USF regulate BRCA2 expression through the BRCA2 promoter.

BRCA1 facilitates stress-induced apoptosis in breast and ovarian cancer cell lines

The BRCA1 tumor suppressor gene has previously been implicated in induction of high levels of apoptosis in osteocarcinoma cell lines. Overexpression of BRCA1 was shown to induce an apoptotic signaling pathway involving the c-Jun N-terminal kinase (JNK), but the signaling steps upstream and downstream of JNK were not delineated. To better understand the role of BRCA1 in apoptosis, we examined the effect of wild-type and C-terminal-truncated dominant negative BRCA1 on breast and ovarian cancer cell lines subjected to a number of different pro-apoptotic stimuli, including growth factor withdrawal, substratum detachment, ionizing radiation, and treatment with anticancer agents. All of these treatments were found to induce substantial levels of apoptosis in the presence of wild-type BRCA1, whereas dominant negative BRCA1 truncation mutants diminished the apoptotic response. Subsequent mapping of the apoptotic pathway induced by growth factor withdrawal demonstrated that BRCA1 enhanced signaling through a pathway that sequentially involved H-Ras, MEKK4, JNK, Fas ligand/Fas interactions, and caspase-9 activation. In addition, the pathway functioned independently of the p53 tumor suppressor. These data suggest that BRCA1 is an important modulator of the response to cellular stress and that loss of this apoptotic potential due to BRCA1 mutations may contribute to tumor development.

Caspase-8-mediated intracellular acidification precedes mitochondrial dysfunction in somatostatin-induced apoptosis

Activation of initiator and effector caspases, mitochondrial changes involving a reduction in its membrane potential and release of cytochrome c (cyt c) into the cytosol, are characteristic features of apoptosis. These changes are associated with cell acidification in some models of apoptosis. The hierarchical relationship between these events has, however, not been deciphered. We have shown that somatostatin (SST), acting via the Src homology 2 bearing tyrosine phosphatase SHP-1, exerts cytotoxic action in MCF-7 cells, and triggers cell acidification and apoptosis. We investigated the temporal sequence of apoptotic events linking caspase activation, acidification, and mitochondrial dysfunction in this system and report here that (i) SHP-1-mediated caspase-8 activation is required for SST-induced decrease in pH(i). (ii) Effector caspases are induced only when there is concomitant acidification. (iii) Decrease in pH(i) is necessary to induce reduction in mitochondrial membrane potential, cyt c release and caspase-9 activation and (iv) depletion of ATP ablates SST-induced cyt c release and caspase-9 activation, but not its ability to induce effector caspases and apoptosis. These data reveal that SHP-1-/caspase-8-mediated acidification occurs at a site other than the mitochondrion and that SST-induced apoptosis is not dependent on disruption of mitochondrial function and caspase-9 activation.

Regulation of acidification and apoptosis by SHP-1 and Bcl-2

Recruitment of the SH2 domain containing cytoplasmic protein-tyrosine phosphatase SHP-1 to the membrane by somatostatin (SST) is an early event in its antiproliferative signaling that induces intracellular acidification-dependent apoptosis in breast cancer cells. Fas ligation also induces acidification-dependent apoptosis in a manner requiring the presence of SHP-1 at the membrane. Moreover, we have recently reported that SHP-1 is required not only for acidification, but also for apoptotic events that follow acidification (Thangaraju, M., Sharma, K., Liu, D., Shen, S. H., and Srikant, C. B. (1999) Cancer Res. 59, 1649-1654). Here we show that ectopically expressed SHP-1 was predominantly membrane-associated and amplified the cytotoxic signaling initiated upon SST receptor activation and Fas ligation. The catalytically inactive mutant of SHP-1 (SHP-1C455S) abolished the ability of the SST agonists to signal apoptosis by preventing the recruitment of wild type SHP-1 to the membrane. Overexpression of the anti-apoptotic protein Bcl-2 in MCF-7 cells inhibited SST-induced apoptosis upstream of acidification by inhibiting p53-dependent induction of Bax as well as by raising the resting pH(i) and attenuating SST-induced decrease in pH(i). By contrast, Bcl-2 failed to prevent apoptosis triggered by direct acidification. These data demonstrate that (i) membrane-associated SHP-1 is required for receptor-mediated cytotoxic signaling that causes intracellular acidification and apoptosis, and (ii) Bcl-2 acts distal to SHP-1 and p53 to prevent SST-induced acidification but cannot inhibit the apoptotic events that ensue intracellular acidification.

Interdependent regulation of intracellular acidification and SHP-1 in apoptosis

The G protein-coupled receptor agonist somatostatin (SST)-induces apoptosis in MCF-7 human breast cancer cells. This is associated with induction of wild-type p53, Bax, and an acidic endonuclease. We have shown recently that its cytotoxic signaling is mediated via membrane-associated SHP-1 and is dependent on decrease in intracellular pH (pHi) to 6.5. Here we investigated the relationship between intracellular acidification and SHP-1 in cytotoxic signaling. Clamping of pHi at 7.25 by the proton-ionophore nigericin abolished SST-signaled apoptosis without affecting its ability to regulate SHP-1, p53, and Bax. Apoptosis could be induced by nigericin clamping of pHi to 6.5. Such acidification-induced apoptosis was not observed at pHi <6.0 or >6.7. pHi-dependent apoptosis was associated with the translocation of SHP-1 to the membrane, enhanced in cells overexpressing SHP-1, and was abolished by its inactive mutant SHP-1C455S. Acidification caused by inhibition of Na+/H+ exchanger and H+ ATPase (pHi = 6.55 and 6.65, respectively) also triggered apoptosis. The effect of concurrent inhibition of Na+/H+ exchanger and H(+)-ATPase on pHi and apoptosis was comparable with that of SST. Acidification-induced, SHP-1-dependent apoptosis occurred in breast cancer cell lines in which SST was cytotoxic (MCF-7 and T47D) or not (MDA-MB-231). We conclude that: (a) SST-induced SHP-1-dependent acidification occurs subsequent to or independent of the induction of p53 and Bax; (b) SST-induced intracellular acidification may arise due to inhibition of Na+/H+ exchanger and H(+)-ATPase; and (c) SHP-1 is necessary not only for agonist-induced acidification but also for the execution of acidification-dependent apoptosis. We suggest that combined targeting of SHP-1 and intracellular acidification may lead to a novel strategy of anticancer therapy bypassing the need for receptor-mediated signaling.

Subtype-selective expression of the five somatostatin receptors (hSSTR1-5) in human pancreatic islet cells: a quantitative double-label immunohistochemical analysis

We have developed a panel of rabbit polyclonal antipeptide antibodies against the five human somatostatin receptor subtypes (hSSTR1-5) and used them to analyze the pattern of expression of hSSTR1-5 in normal human islet cells by quantitative double-label confocal fluorescence immunocytochemistry. All five hSSTR subtypes were variably expressed in islets. The number of SSTR immunopositive cells showed a rank order of SSTR1 > SSTR5 > SSTR2 > SSTR3 > SSTR4. SSTR1 was strongly colocalized with insulin in all beta-cells. SSTR5 was also an abundant isotype, being colocalized in 87% of beta-cells. SSTR2 was found in 46% of beta-cells, whereas SSTR3 and SSTR4 were relatively poorly expressed. SSTR2 was strongly colocalized with glucagon in 89% of alpha-cells, whereas SSTR5 and SSTR1 colocalized with glucagon in 35 and 26% of alpha-cells, respectively. SSTR3 was detected in occasional alpha-cells, and SSTR4 was absent. SSTR5 was preferentially expressed in 75% of SST-positive cells and was the principal delta-cell SSTR subtype, whereas SSTR1-3 were colocalized in only a few delta-cells, and SSTR4 was absent. These studies reveal predominant expression of SSTR1, SSTR2, and SSTR5 in human islets. Beta-cells, alpha-cells, and delta-cells each express multiple SSTR isoforms, beta-cells being rich in SSTR1 and SSTR5, alpha-cells in SSTR2, and delta-cells in SSTR5. Although there is no absolute specificity of any SSTR for an islet cell type, SSTR1 is beta-cell selective, and SSTR2 is alpha-cell selective. SSTR5 is well expressed in beta-cells and delta-cells and moderately well expressed in alpha-cells, and thereby it lacks the islet cell selectivity displayed by SSTR1 and SSTR2. Subtype-selective SSTR expression in islet cells could be the basis for preferential insulin suppression by SSTR1-specific ligands and of glucagon inhibition by SSTR2-selective compounds.

The salubrious effect of tamoxifen [correction of Tamaxifen] on serum marker enzymes, glycoproteins, and lysosomal enzymes level in breast cancer woman

Tumour markers correlate strongly with prognosis based on tumour burden and surgical resectability. If chemotherapy is extremely effective in certain stage of the disease, the sensitive marker may be of great use in monitoring disease response and drug treatment. Hence, this study was launched to evaluate the changes in tumour marker enzymes like lactate dehydrogenase (LDH), glutamate oxaloacetate transaminase (SGOT), glutamate pyruvate transaminase (SGPT), alkaline phosphatase, and acid phosphatase in before and after 3 and 6 months tamoxifen treated breast cancer patients. In addition, the changes in serum glycoproteins viz., hexose, hexosamine, and sialic acid and lysosomal enzymes such as N-acetyl-beta-D-glucosaminidase, beta-D-galactosidase, and beta-D-glucuronidase were analysed in these patients. These values were compared with their age matched healthy control subjects. At 6 months evaluation, the tamoxifen treated postmenopausal breast cancer women showed a statistically significant decreased (p < 0.001, 0.05 respectively) levels of LDH, SGOT, SGPT, alkaline and acid phosphatases than their baseline values. Similarly, the levels of hexose, hexosamine, and sialic acid and N-acetyl-beta-D-glucosaminidase, beta-D-galactosidase, and beta-D-glucuronidase were decreased significantly (p < 0.001) in tamoxifen received postmenopausal women. The result of this study suggested that tamoxifen potentially retard the metastasis of breast cancer as well as the bone demineralisation in postmenopausal breast cancer women. Thus, tamoxifen may also have its antitumour activity through its beneficial effects on tumour marker enzymes and serum proteins in breast cancer women.

The salubrious effects of ascorbic acid on cyclophosphamide instigated lipid abnormalities in fibrosarcoma bearing rats

The combined effect of cyclophosphamide and ascorbic acid on plasma lipids and lipoprotein profiles are important since, ascorbic acid encumbered the lipid abnormalities initiated by cyclophosphamide during cancer chemotherapy. Hence, the study was launched to appraise the salutary role of ascorbic acid in cyclophosphamide administered fibrosarcoma bearing rats. Fibrosarcoma cell line induced rats were treated with cyclophosphamide (10 mg/kg body weight) and ascorbic acid (200 mg/kg body weight) individually and in combination for 28 days. The concentration of plasma lipids and lipoprotein profiles were determined in control and experimental animals. The untreated, as well as cyclophosphamide administered fibrosarcoma bearing rats, divulged significantly increased levels of plasma total cholesterol, triglycerides, phospholipids, VLDL- and LDL-cholesterol, as compared with their respective control animals. In contrast, ester and HDL-cholesterol levels exhibited a marked decrease in these animals. Similar observations were also noticed in liver lipid values, as well. However, these lipid abnormalities were corrected by the co-administration of ascorbic acid. These results suggested, that some clinical entanglement of cyclophosphamide was refrained by co-administration of ascorbic acid in tumor stress condition.

Effect of tamoxifen on lipids and lipid metabolising marker enzymes in experimental atherosclerosis in Wistar rats

Tamoxifen, a non-steroidal anti-oestrogen, is used in the treatment of breast cancer, both receptor positive and negative tumours. It also possesses weak oestrogenic activity which forms the basis of this study. Tamoxifen (2 different dosages) was administered through diet (10 mg/kg diet and 20 mg/kg diet) to experimental atherosclerosis induced female rats to assess the effect of tamoxifen on plasma lipid levels, lipoprotein cholesterol level and on the activity of lipid metabolising enzymes. The plasma total lipid level was increased in atherosclerosis suffering animals compared to control animals with concomitant changes in the activity of lipid metabolising enzymes. HDL-cholesterol was decreased while LDL-cholesterol and VLDL-cholesterol were increased in the atherosclerosis induced group. Cholesterol and free cholesterol were decreased in tamoxifen treated groups while the other lipids show a moderate increase. HDL-cholesterol was increased but LDL-cholesterol was decreased in the tamoxifen treated groups. The higher dosage tamoxifen given group animals show significantly favourable results from therapy stand point when compared to diseased group.

Alpha-tocopherol ameliorates cyclophosphamide-induced hyperlipidemia in fibrosarcoma-bearing rats

Cyclophosphamide, an alkylating agent, is currently being used for the treatment of various types of cancer, either alone or in combination with other cytostatic drugs. However, cyclophosphamide has a detrimental effect on lipid metabolism and causes hyperlipidemia in patients. Since alpha-tocopherol is known to reduce hyperlipidemia, we have investigated the effects of adding alpha-tocopherol to the cyclophosphamide treatment. Our study, carried out on fibrosarcoma-bearing rats, shows that alpha-tocopherol markedly reduces cyclophosphamide-induced hyperlipidemia and brings lipid metabolism down to values observed in untreated controls.

Plasma lipids and lipoprotein alterations in tamoxifen-treated breast cancer women in relation to the menopausal status

Plasma lipids and lipoprotein profiles were monitored in 72 postmenopausal and 29 premenopausal breast cancer women who were treated with tamoxifen (20 mg twice a day) for 6 months. The levels of total and free cholesterol and LDL cholesterol were markedly (P < 0.001 for each) decreased in 3 and 6 month tamoxifen-treated postmenopausal women than the baseline values of untreated breast cancer patients. On the contrary, plasma ester cholesterol, triglycerides, VLDL and HDL cholesterol levels were increased significantly in these patients. In the case of premenopausal women the lipid lowering potential of tamoxifen was markedly retarded. These results indicated that tamoxifen - treatment was more beneficial and estrogenic in postmenopausal women's lipids. In premenopausal breast cancer women, tamoxifen was antiestrogenic and less beneficial. Hence, the difference in plasma lipids and lipoprotein content was no greater among those receiving tamoxifen and baseline values of premeno - pausal women. These results indicate that tamoxifen-treatment has a more beneficial effect in postmenopausal women, with a likely reduction in cardiovascular disease, than in premenopausal subjects.

Effect of administering cyclophosphamide and vitamin E on the levels of tumor-marker enzymes in rats with experimentally induced fibrosarcoma

Cyclophosphamide, and antineoplastic drug, and vitamin E, the common antioxidant present in the diet, were administered in separate dosages and in combination to animals (rats) with fibrosarcoma, metastatic tumor of the connective tissues, induced. The anticancer drug (20 mg/kg body weight) and the vitamin-E (400 mg/kg body weight) was administered for a period of 28 days from the day of tumor transplantation. The individual and the combined effects of these two substances were investigated by checking the growth of the tumor. Tumor markers like lactate dehydrogenase (LDH), serum glutamate pyruvate transminase (SGPT), serum glutamate oxaloacetate transaminase (SGOT), acid phosphatase, and alkaline phosphatase were analyzed for the changes in their concentration in serum, liver, and kidney to assess the success of the therapy. The increased level of the enzymes in the fibrosarcoma-suffering rats (GPII) was reduced by cyclophosphamide treatment (GP III) and vitamin E administration (GP IV). Among the treated groups, the combination therapy (GP V) showed greater efficacy in the treatment of fibrosarcoma than did individual administration, as there was more reduction in the levels of enzymes in Group V than those in to Groups III and IV. The enzyme levels were brought to near the normal level.

Effect of tamoxifen on erythrocyte membrane lipids, lipid peroxides, and antioxidative enzymes in breast cancer women

Fasting blood samples were taken from 64 tamoxifen-treated postmenopausal women with early stage breast cancer. The levels of erythrocyte lipid peroxidation and the status of erythrocyte detoxifying enzymes were analyzed in untreated and treated patients for 3 months and 6 months with tamoxifen. Erythrocyte membrane lipid peroxidation and membrane cholesterol, phospholipid were also determined in all the patients. The 3 months and 6 months tamoxifen-treated patients showed significantly decreased levels of erythrocyte, erythrocyte membrane lipid peroxide with concomitantly increased levels of detoxifying enzymes when compared with baseline values of untreated women. Erythrocyte membrane cholesterol and phospholipid levels were markedly decreased in tamoxifen-treated patients than in untreated women. An interesting finding of this study indicates that the lipid peroxide, as well as, the lipid lowering efficacy of tamoxifen, was increased in patients with greater levels of baseline lipid and lipid peroxides in their erythrocyte membrane. These results indicate that tamoxifen is a potent suppressor of lipid peroxide formation through the favorable effects on membrane lipids and protective enzyme system.

Effect of tamoxifen on lipid peroxide and antioxidative system in postmenopausal women with breast cancer

BACKGROUND

Current evidence clearly indicates that free radicals play a prominent role in the incidence and development of breast cancer. Available literature suggests that tamoxifen is a potent suppressor of lipid peroxide formation in both animal and human systems. The purpose of this study was to understand the rate of lipid peroxidation and the status of antioxidants in tamoxifen-treated postmenopausal women with breast cancer.

METHODS

A short term evaluation of 6 months' tamoxifen therapy (10 mg twice a day) in 64 postmenopausal women was conducted. The rate of serum lipid peroxidation and the status of enzymic and nonenzymic antioxidants were evaluated before and after 3 and 6 months' tamoxifen treatment.

RESULTS

At 3 and 6 months' evaluation, tamoxifen-treated patients showed a significantly decreased concentration of malondialdehyde (P < 0.001), an end product of lipid peroxidation, and remarkably increased levels of enzymic and nonenzymic antioxidants. In addition to that, the concentrations of serum selenium and vitamins A, C, and E were increased significantly (P < 0.01 for each) in these patients.

CONCLUSION

The results suggest that tamoxifen therapy exerts significant positive effects on the rate of lipid peroxidation and protective systems in postmenopausal women with breast cancer.

Effect of alpha-tocopherol on lipid peroxidation and antioxidant system in fibrosarcoma bearing rats

The anticarcinogenic activity of alpha-tocopherol (Vitamin E) was tried in fibrosarcoma induced rats through its antioxidative potential. The rate of formation of malondialdehyde (MDA), the end product of lipid peroxidation was analysed in alpha-tocopherol (400 mg/kg body weight) treated and untreated fibrosarcoma bearing rats with respective controls. The levels of non-enzymic antioxidants like, glutathione and vitamin E, and enzymic antioxidants viz., catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GSH-PX), and glutathione-S-transferase (GST) were assayed as well. Significantly increased (p < 0.001) level of lipid peroxide was observed with concomitant decreases in the level of enzymic and non-enzymic antioxidants in fibrosarcoma bearing rats when compared with control animals. In alpha-tocopherol supplemented animals, the corrected level of these parameters were observed likely to near normal values. Thus, alpha-tocopherol can be accepted to pose first line of defense mechanism against excessively formed reactive species due to impaired antioxidant systems in fibrosarcoma conditions, that cause membrane damage leading to deleterious effects.

Effect of tamoxifen on plasma lipids and lipoproteins in postmenopausal women with breast cancer

BACKGROUND

Adjuvant tamoxifen therapy is given to large and increasing numbers of women with early-stage breast cancer. The effects of this drug on plasma lipids and lipoprotein profiles are important, because cardiovascular disease also develops over time in a large percentage of tamoxifen-treated postmenopausal women. The purpose of the study was to evaluate the effects of tamoxifen on plasma lipid and lipoprotein profiles in postmenopausal Indian women who were disease-free after primary treatment for breast cancer.

METHODS

A short-term evaluation of 6 months of tamoxifen therapy (10 mg twice a day) in 45 postmenopausal women was conducted. The plasma lipids and lipoprotein levels were evaluated before and after 3 and 6 months of tamoxifen treatment.

RESULTS

At 3 and 6 months' evaluation, patients receiving tamoxifen showed significantly decreased levels of total cholesterol, free cholesterol, and low-density lipoprotein cholesterol (P < 0.001 for each) and increased levels of plasma triglycerides, free fatty acids, very low density lipoprotein cholesterol, and high-density lipoprotein cholesterol.

CONCLUSION

The results suggest that tamoxifen therapy benefits postmenopausal patients with breast cancer, with likely reduction in the risk of cardiovascular disease.

Changes observed in antioxidant system in the blood of postmenopausal women with breast cancer

From experimental studies and epidemiological data, it can be inferred that lipid peroxidation is increased in cancer patients. Cases of post-menopausal, untreated women with benign and malignant breast tumours, were compared with their age matched controls in their serum lipid peroxides, antioxidant vitamins (E and C), serum selenium and serum ceruloplasmin. Erythrocyte and its membrane lipid peroxidation and antioxidant enzymes (catalase, superoxide dismutase, glutathione peroxidase and glutathione-S-transferase) levels were also analyzed. Significant increase in circulating lipid peroxides, ceruloplasmin and significant decrease in antioxidant vitamins and selenium were observed in breast cancer women. The erythrocyte and its membrane lipid peroxidation was increased significantly and severe impairment of antioxidant potential was observed in breast cancer women.