Nicotine plasma concentration in smokers ranges in between . and mM , with a peak level occurring within min from smoking initiation and declining with an typical elimination half existence of about h . Nicotine can exert these effects via nAChR activation, also in non neuronal cells . Notably, a nAChR was recognized within the human colon cancer cell lines HT and DLD , during which NNK, a carcinogen formed by nicotine nitrozation, enhanced cell migration with the mediation of this receptor . Furthermore, nicotine promoted cell proliferation in HT line by means of a nAChR activation, with the contribution of b adrenoceptors , and in SW colon cancer cells as a result of activation of epidermal development element receptor and c Src, together with protein expression of LOX . In our study, nicotine induced a statistically significant enhance inside the proliferation fee of Caco and HCT colon cancer cells. In both cell lines, remedy that has a BTX, a aggressive antagonist of the subunit of nicotinic receptor, inhibited nicotine induced effects on cell proliferation. Indeed, within a BTX taken care of cells mitotic fee turned back to control levels, indicating that nicotine induced cell development was largely mediated by a nAChR .
Nicotine effects on Caco and HCT cells will not be limited to cell development. In actual fact, we observed a statistically considerable reduce of apoptosis in nicotine handled cells in each common and serum free of charge culture conditions. As being a matter of truth, it is well known that serum deprivation induces apoptosis in cultured cells. To order Vorinostat selleck chemicals amplify the apoptotic price and maximize nicotine antiapoptotic impact, we repeated the experiments in serum absolutely free situations. The addition of the BTX counteracts these effects and restores an apoptotic fee just like that observed in manage cultures, for that reason suggesting the involvement of the nAChR. It really is extensively acknowledged that nicotine inhibits apoptosis in lots of distinct tumors too as in regular cells, and this process appears to be mediated by non neuronal nAChRs. Then again, controversy exists with regards to the precise subunit responsible for this impact.
Actually, although there exists evidence to the involvement in the dihydro b erythroidine delicate a b subunits of nAChR from the inhibition of apoptosis in both bronchial Rigosertib epithelial and non modest cell lung cancer cells , several researchers have proven the implication of the nAChR in the resistance to apoptosis of different cell sorts . To our best awareness, just one research has previously addressed nicotine induced effects on apoptosis of colon cancer cells. Then again, information offered through the paper of Crowley Weber et al. highlighted that nicotine appears to increase the apoptotic rate in colon cancer cells, in lieu of to cut back it.
Monthly Archives: May 2013
Yet, when ASO Bcl and ASO Clus were mixed, whilst there was a red
Having said that, when ASO Bcl and ASO Clus were mixed, although there was a decrease in the levels with the proteins, the anticipated synergy in enhancing sensitivity to TRAIL was not observed. In fact, in most cell lines the results had been discovered to be even decrease than people of ASO Bcl transfection alone. This may well be explained in element by the probable aggressive transfection uptake of ASOBcl and ASO Clus. Total our information propose that down regulation of Bcl by ASO Bcl has by far the most potent effect on expanding TRAIL sensitivity and Clus expression might also possess a position in TCCB TRAIL resistance. Transforming development issue was initially isolated like a transforming factor of usual rat kidney fibroblasts. Subsequent investigations demonstrated that TGF is actually a crucial detrimental regulator with the immune system. TGF knockout mice die of diffuse autoimmune response to weeks just after birth. Even more scientific studies showed that TGF inhibits interleukin production, top rated to your inhibition of T cell proliferation.
Moreover, TGF inhibits the potential of na?ve CD and CD T cells to develop into mature effector T cells, Th or Th, or cytotoxic T0070907 selleck selleck lymphocytes, respectively. In macrophages and monocytes TGF is stimulatory and inhibitory. TGF is actually a potent chemoattractant of human blood monocytes and it activates phagocytic action in macrophages. However, TGF has also been shown to deactivate macrophages by suppressing nitric oxide and reactive oxygen intermediates. TGF signals go through a heteromeric complicated of style I and II receptors . Ligand binding initially takes place with TRII. In flip, TRI is recruited to the complex and TRII cross phosphorylates TRI to propagate signaling through smads, a loved ones of transcription factors. A lot more not too long ago Smad independent TGF signaling pathways have already been recognized. In many reliable malignancies TGF more than expression continues to be reported while in the context of low or reduction of TGF receptors. For instance, in prostate cancer improved TGF levels happen to be reported in tissues and serum in association by using a reduction of TRI and TRI expression.
The improved TGF levels promote tumor progression by suppressing host immune response and promoting angiogenesis. Therefore, a potential anticancer therapeutic system certainly is the inhibition of TGF signaling. A short while ago a novel modest molecule inhibitor of TRI ALK , designated IN Sorafenib , has become reported to inhibit renal fibrosis. From the current study we further characterized the specificity of IN likewise because the effect on prostate cancer cells. We report that IN blocks TGF and activin signaling, when simultaneously decreasing tumor take as well as the tumor growth rate in mice with established prostate cancer xenografts.
ATM phosphorylates a p peptide on serine in vitro and this phosph
ATM phosphorylates a p peptide on serine in vitro and this phosphorylation correlates with p protein stabilization in cells exposed to IR . p protein and p serine phosphorylation had been evident while in the soluble nuclear fraction created from cells exposed to both ?Gy particles emitted by P or ?. Gy particles emitted by P . p protein and p serine phosphorylation had been higher while in the soluble nuclear fraction created from cells exposed to both ?Gy particles emitted by P or?. Gy particles emitted by P . Additional, p protein and p serine phosphorylation had been better within the soluble nuclear fraction created from cells exposed to P orthophosphate than P orthophosphate.pprotein andp serine phosphorylation had been induced inside the cytoplasmic and micrococcal nuclease digested chromatin fractions created from cells exposed to either?Gy particles emitted by Por?. Gy particles emitted by P . In all samples the improve in p protein and p serine phosphorylation was prevented by concurrent exposure towards the selective inhibitor of ATM kinase exercise KU . ATM kinase exercise correlates with ATM serine phosphorylation .
ATM serine phosphorylation was evident during the micrococcal nuclease digested chromatin fraction produced from cells exposed to both?Gy particles emitted by Por?. Gy particles emitted by P . ATM serine phosphorylation was better IOX2 in cells exposed to P orthophosphate than in cells exposed to P orthophosphate. ATM serine phosphorylation was prevented by concurrent exposure to KU. ATM protein accumulated in the micrococcal nuclease digested chromatin fraction generated from cells exposed to either Porthophosphate or P orthophosphate and concurrently exposed for the selective inhibitor of ATM kinase exercise KU. The protein kinase CHK is phosphorylated and activated in response to DNA harm by ionizing radiation . Phosphorylation on CHK threonine is ATM kinase dependent in response to IR and CHK threonine phosphorylation is crucial for activation of CHK kinase activity . CHK threonine phosphorylation was induced in cells exposed to ?Gy particles emitted by P or ?. Gy particles emitted by P .
The increase in CHK threonine phosphorylation was higher in cells exposed to particles emitted by P than in cells exposed to particles emitted by P. Even further, ATM dependent CHK threonine phosphorylation was prevented by concurrent exposure to KU Accumulation of ATM inside the chromatin fraction in cells exposed to ? particles emitted by P or P We established the relative volume of ATM in cell fractions generated from IMR taken care of with both vehicle or KU through an Rho kinase inhibitor selleck chemicals publicity to ?. Gy particles emitted by P . This was simply because our observation that ATM protein accumulated from the micrococcal nuclease digested chromatin fraction generated from cells exposed to both P orthophosphate or Porthophosphate as well as selective inhibitor of ATM kinase action KU was sudden .
These data implicate the ATM Chk CdcC pathway from the cell cycle
These information implicate the ATM Chk CdcC pathway while in the cell cycle arrest induced by jaceosidin ERK is involved with the jaceosidin induced G M cell cycle arrest It’s been demonstrated that jaceosidin induced apoptosis is mediated by regulation of ERK activation likewise as ROS accumulation . In this regard, we investigated the involvement on the ERK signaling in development inhibitory result by jaceosidin in endometrial cancer. Interestingly, jaceosidin greater ERK phosphorylation . Additionally, jaceosidin induced development inhibition of HecA cells was substantially abrogated in the presence of the ERK inhibitor, PD . These findings are steady with past reports showing that ERK activation might contribute on the activation with the ATM, Chk , and CdcC pathway Discussion Jaceosidin, a naturally happening dietary flavonoid isolated from Artemisia princeps, has anti inflammatory, anti oxidative, and anti tumor properties . Jaceosidin is reported to get growth inhibitory results in quite a few cancer cell lines including breast, ovarian, cervical, prostate, colon cancer, and glioblastoma cells .
On the other hand, the mechanism of action of jaceosidin about the cell development inhibition in cervical, prostate, and colon cancer hasn’t been elucidated . Then again, the growthinhibitory impact of jaceosidin was associated with all the induction of apoptosis in ras transformed human breast epithelial cells and CAOV ovarian cancer cells . The proapoptotic activity of jaceosidin in ras transformed human breast epithelial cells was mediated by ROS accumulation and inhibition of ERK and JNK activation supplier FTY720 . In CAOV cells, jaceosidin induced apoptosis involved activation of caspase by means of mitochondrial pathway . Moreover, jaceosidin induced apoptosis in U glioblastoma cells as a result of G M phase arrest . From the current review, we found that jaceosidin induces development inhibition in human endometrial cancer cells by raising the population of cells inside the G M phase on the cell cycle. These information suggested that jaceosidin has cell linespecific growth inhibitory result in different cancer cells.
The precise mechanism in the distinctive responses of cancer cells to jaceosidin stays for being even more investigated. Cell cycle blockade is thought to be a highly effective system for eliminating cancer cells . Without a doubt, agents that inhibit cell cycle progression, such as mifepristone and histone deacetylase inhibitors, happen to be Screening Library reported as possible therapeutics for endometrial cancers . Regulation on the cell cycle takes place at two leading checkpoints, one at the G S transition and 1 with the G M transition. The G M checkpoint plays a critical role inside the maintenance of chromosomal integrity by allowing cells to restore DNA harm just before entering mitosis. Cdc , a cyclin dependent kinase, may be a primary regulator within the cell cycle at this checkpoint .
We studied the expression of Forkhead protein , particularly p FO
We studied the expression of Forkhead protein , especially p FOXO plus the cyclic AMP response element binding protein , especially p CREB , which promotes neuronal survival when phosphorylated. Our benefits propose that h of CGN S K withdrawal inhibits p FOXO Ser and p CREB Ser phosphorylation, though treatment method with M SP prevents this dephosphorylation mediated inhibition . The phosphorylation of each proteins when CGNs were taken care of with SP could also clarify, in component, the neuroprotective properties of this drug on this apoptotic model, and once again confirms that Akt remains activate when SP is implemented to inhibit JNK. In regard to CDK, a further cyclin dependent kinase that may be involved in the practice of neuronal apoptosis , Akt has not long ago been proven to immediately regulate CDK activity via the raise of p protein expression, which activates CDK . Thus, the following experiments we carried out sought to further investigate no matter whether SP could protect against cdk p breakdown and the formation of professional apoptotic cdk p.
Right here, Western blot evaluation showed that SP increased the p p ratio SMI-4a dissolve solubility selleck chemicals and prevented the breakdown of cdk p . Eventually, to determine whether Akt is involved in SP mediated neuroprotection, we subjected CGNs to a neuroprotective therapy within the presence of LY, a PIK Akt inhibitor, soon after S K withdrawal. The PIK AKT inhibitor, in aspect, counteracted the antiapoptotic results of SP against S K withdrawal, this getting demonstrated from the vital raise in DNA fragmentation and also the quantity of condensed nuclei . To further figure out no matter if the neuroprotective results of SP may be mediated by the activation of the Akt pathway we investigated the effects of this drug on LY mediated neurotoxicity in CGNs. We first determined the concentrations of LY that mediated CGN cell reduction . Applying the MTT assay and PI staining by movement cytometry, we located that CGN viability was appreciably lowered just after h of treatment with m PIK inhibitor ; SP, in a concentration choice of M, protected CGNs from loss of cell viability and DNA fragmentation .
Evaluation of probable pathways associated with sustaining FTY720 clinical trial Akt activated by SP treatment For you to elucidate the mechanism by which SP maintains Akt activation we studied previously recognized pathways that activate Akt. For instance, it is recognized that the PIK pathway may be activated by a number of ligands this kind of as N methyl D aspartate , neurotrophic variables, insulin and others. To find out if the antiapoptotic effects of SP are as a consequence of interaction with neurotrophin receptors, we used Ka, a potent TrkB inhibitor. Treatment method of CGNs with S K withdrawal during the presence of SP was, even so, not altered by this compound .
Considering PEG modified liposomes are knownto be secure in blood
Because PEG modified liposomes are knownto be steady in blood circulation, it appears to supply SU to tumor tissues by endothelial cell layer by EPR effect . As a result, not only passive targeting, actively focusing on to angiogenic endothelial cells may be a crucial aspect in drug delivery of angiogenesis inhibitors. In conclusion, we showed that APRPG PEG Lip SU suppressed tumor angiogenesis and prolonged the survival instances of tumor bearing mice, indicating that APRPG modified liposomes correctly provide SU to angiogenic endothelial cells. The existing study suggest that angiogenic vessel targeted liposomes are useful carriers of angiogenesis inhibitors for antiangiogenic cancer treatment. The fibroblast development component household plays many different roles in determining and regulating functions of some endocrine related tissues or organs . With the known members on the loved ones, FGF is usually a novel member iden tified by Nishimura et al Accumulating proof signifies the position of FGF as a vital regulator of long-term energy stability and metabolic process.
Mice lacking FGF cannot react appropriately to a ketogenic food plan, resulting in an impaired capability to mobilize and use lipids . The FGF expresses pre dominantly in pancreas, liver and adipose tissues, and rather much less in other organs, which includes the testis . Countless studies have focused over the function of FGF in metabolic regulation from the liver, body fat, and in some cases skeletal muscle . However, the PD98059 selleck position of FGF in other organs hasn’t been properly addressed. The expression of FGF mRNA was found in the testis , but what’s the biological function of FGF during the testis remains unclear. Actually, it has been appreciated that the other FGF loved ones this kind of as FGF and are also expressed in the male reproductive tract and are intimately involved with tes ticular maturation, Sertoli cell proliferation and differentiation ; some members of FGF household such as FGF play very important anti apoptotic role inside the safety in the testicular cells towards the toxic result . Testicular apoptotic cell death takes place in lots of disorders, which include the usual spermatogenesis and in addition chronic conditions this kind of as diabetes .
We have demonstrated that diabetes induces testicular apoptotic cell death predominantly as a result of mitochondrial Ostarine molecular weight and endoplasmic reticulum worry connected cell death pathways, which might be metabolic abnormality induced oxidative injury . No matter whether FGF as an essential metabolic mediator can be involved with the maintenance within the spermatogenesis and if FGF protects the germ cells from diabetes induced apoptotic cell death have never been investigated. Reportedly FGF improves the survival of pancreatic cells . Islets and INS E cells isolated from FGF treated diabetic rats have been partially protected from glucose , lipid , and cytokine induced apoptosis .
2nd, the senescenceassociated b galactosidase activity of cells
Second, the senescenceassociated b galactosidase activity of cells at passage was undetecinhibitors, since it was in cells at passage . Third, the basal degree of P, an indicator of growth arrest, was the exact same in early and late passage fibroblasts . These success indicate that late passage cells are certainly not in replicative senescence Telomere length decreases throughout these passages Its nicely documented that, with escalating passage degree, the telomeres in principal human fibroblasts undergo telomere shortening . Nevertheless, the moment human fibroblasts are immortalized , telomerase is reactivated and telomere length returns to that of youthful cells . Although our human fibroblasts were not senescent at passage , it remained conceivable they had spontaneously immortalized. This would suggest they would by no means enter senescence. Telomere length was measured making use of the terminal restriction fragment procedure . In our hands, human fibroblasts passaged times had a suggest telomere length of kb, whereas the same fibroblast strain passaged or occasions had indicate telomere lengths of .
and . kb, respectively . The continual shortening of telomeres, even at passage , shows that these skin fibroblasts haven’t immortalized Acquired apoptosis resistance at late passage is connected to altered UVB regulation of BCL household members Apoptosis and apoptosis resistance are governed by a network of pro and anti apoptotic proteins . To determine the mechanism of passage degree dependent downregulation of UVB induced ATP-competitive Proteasome inhibitor selleck apoptosis, we examined important members of this network. P Inhibitor , upper left panel exhibits that P accumulated as early as h soon after UVB irradiation in each early passage and late passage fibroblasts. Having said that, this accumulation plateaued at h in early passage cells but in late passage cells , the plateau appeared at h as well as maximal level of induction was reduce. BCL loved ones BCL household proteins are a significant family members of professional apoptotic and anti apoptotic proteins that regulate apoptosis at peri mitochondrial websites.
A cellular anxiety which include UVB is regarded to set off induction of pro apoptotic members like BAX and degradation of anti apoptotic proteins like BCL and BCL xL . Simply because P is really a direct Sunitinib transcriptional activator from the proapoptotic protein BAX, we anticipated that regulation of BAX following UVB would track that of P . Accordingly, we noticed UVinduction of BAX in early passage fibroblasts but not in late passage cells, wherever the degree remained unchanged soon after UV . The difference involving the NoUV and the h lane in older cells isn’t statistically substantial . However, the basal degree of BAX was higher in older cells, in actual fact equal towards the UVB induced level in the younger cells. As a result, this result alone would not describe the apoptosis resistance of older fibroblasts.
No statistically important decrease in thymidine incorporation wa
No statistically considerable decrease in thymidine incorporation was observed when cultures were incubated with API CJ Ome alone. PIK AKT pathway is concerned while in the survival of several cell varieties, as well as differentiated neurons of your mouse retina . So as to exclude the probability that API CJ Ome inhibited ADP induced thymidine incorporation by blocking survival of late creating retinal progenitors, the impact of this compound on cell survival was investigated. Retinal cell cultures at EC have been pre incubated for h with M ADP from the presence or not of . M API CJ Ome and processed for MTT viability assay as described in Part . No considerable decrease in cell viability was observed when cultures have been incubated together with the inhibitor or using the inhibitor plus ADP , as in contrast to non taken care of or ADP treated cultures. Considering each the PIK and AKT inhibitors LY and API CJ Ome decreased thymidine incorporation induced by nucleotides from the cultures, their result may be thanks to a decrease inside the survival on the specific population of proliferating retinal cells within the cultures.
As a way to exclude this likelihood, retinal cultures at EC have been incubated with . Ci thymidine for h to label proliferating retinal progenitors after which incubated with . M API CJ Ome or M LY, Vismodegib kinase inhibitor while in the presence or not of M ADP, for an additional h period. Inhibitor shows that no lessen while in the ranges of pre integrated thymidine may be observed in cultures handled with these compounds, neither in presence or absence of ADP. D style cyclins are proteins connected to the G S transition on the cell cycle and that handle the decision of progenitors to enter S phase and divide in response to mitogens . Within the establishing retina, cyclin D expression is greater by mitogens . The effect of M ADP to the expression of cyclin D in retinal cultured cells at EC is shown in Inhibitor A. A rise of approximately above non stimulated amounts could presently be observed soon after a h incubation within the cultures with all the nucleotide.
After h of incubation, ADP induced a increased expand in cyclin D expression . Moreover, the two LY and U , inhibitors of PIK and MEK, respectively, considerably blocked ADP induced raise in cyclin D . Cyclin PD98059 D amounts decreased from . and in ADP taken care of cultures to . and . of basal levels in cultures incubated with the nucleotide plus LY or U, respectively. Cell cycle arrest ordinarily is attained by blockade of cyclin CDKs complexes by CDK inhibitors . While in the retina, while cyclin D usually induces cell cycle progression, the CKI pkip is concerned in cell cycle exit of progenitors . Also, within the mouse retina, this protein is down regulated when retinal progenitors are incubated with nucleotides .
In contrast, during the OAW R cell line, acquisition of resistanc
In contrast, inside the OAW R cell line, acquisition of resistance to cisplatin induced apoptosis was associated by using a reduction of ERK activation in response to therapy . In this research, we very first characterized the effects of , DCPE within the OAW R cell line to find out whether or not this molecule could both effectively induce ERK activation and show anticancer properties within this ovarian carcinoma cell line. We then extended our examine to your impact of the , DCPE therapy on 3 other ovarian carcinoma cell lines which displayed various patterns of basal ERK activation. We ultimately examined whether or not , DCPE could sensitize OAW R resistant cells to the apoptotic effect of cisplatin, specially by restoring ERK phosphorylation. The chemoresistant OAW R variant was obtained by intermittently exposing the OAW cell line to escalating concentrations of cisplatin , as previously described . Immediately after each and every h remedy, the cultures have been maintained for quite a few weeks by usual modifications in the culture medium, right up until drug surviving cells recovered a usual development pattern.
The IGROV R resistant subline had been established inside the similar way, from your delicate IGROV cell line . OAW R and OAW cell lines had been grown in DMEM supplemented with mg l glucose, mM Glutamax?, mM sodium pyruvate, fetal calf serum, mM sodium bicarbonate and UI l recombinant human insulin . SKOV and IGROV R cell lines had been grown in RPMI medium supplemented with mM Glutamax?, mM HEPES, fetal calf serum and mM sodium bicarbonate ROCK inhibitor selleckchem . The cells have been maintained at C in a CO humidified ambiance. OAW R and IGROV R cell lines had been handled month-to-month with g ml CDDP to help keep their large level of chemoresistance. Chemicals , DCPE was obtained from ChemBridge Corporation . It was extemporaneously dissolved at mM in dimethyl sulfoxide and diluted thereafter in medium. Business remedy of cisplatin was obtained from Merck and diluted in serumfree medium. Drug treatment Exponentially expanding cells had been continuously exposed to , DCPE for your indicated instances.
DMSO, by which , DCPE was dissolved, was put to use like a handle because it didn’t have any impact on cells inside the thought of choice of concentrations. The mixture remedy consisted of a h exposure to , DCPE, interrupted by a h remedy with CDDP Sodium Monofluorophosphate selleck chemicals concerning the th and also the th hour after the beginning on the , DCPE exposure. All of the presented experiments are carried out at the very least in duplicate. XTT test Cells have been seeded in properly plates and exposed to increasing concentrations of , DCPE , h soon after plating. The cytotoxicity of , DCPE was assessed through the XTT PMS metabolized dye assay according to Scudiero et al which measures cell viability and h after the beginning in the publicity .
Blend index values were calculated using the classic isobologram
Blend index values were calculated applying the traditional isobologram equation and indicate synergy or additivity . We observed a synergistic interaction involving metformin and cisplatin on apoptosis induction having a CI of . and . for OVCAR and OVCAR , respectively. Again, caspase activity paralleled the result of metformin, alone or in combination with cisplatin . Effect with the combination of metformin and cisplatin on professional survival and professional apoptotic proteins on the Bcl household in OVCAR and OVCAR cell lines We upcoming evaluated the combined impact of metformin and cisplatin about the amounts of professional survival Bcl relatives proteins. In OVCAR , the addition of cisplatin to metformin did not drastically modulate the levels of any pro survival and professional apoptotic proteins with the Bcl loved ones compared to metformin alone, whereas in OVCAR , the combination of both drugs enhanced their impact on the professional and anti apoptotic proteins of the Bcl household. Discussion Epithelial ovarian cancer stands out as the top rated cause of death amongst gynecological cancers and close to of patients with advancedstage ailment will go through recurrence .
This is certainly triggered by the Ponatinib selleck chemicals development of resistance to existing therapies, implying the need to develop novel therapeutic modalities with progressive mechanisms of action. Metformin is used for numerous decades for the treatment method of sort diabetes and includes a established track record of becoming tremendously successful with minimal toxicity. It is readily available as a stable, oral drug and is remarkably economical. Interestingly, the concept that this biguanide might possibly be a promising anti cancer drug was very first formulated from the early s . Later on on, two population scientific studies provided preliminary evidence that metformin could possibly lower cancer chance and enhance prognosis in type diabetic sufferers . We now have previously reported, for your to begin with time, that metformin lowers epithelial ovarian cancer cell proliferation, partly through AMPK activation . Not long ago, these final results had been confirmed in each cisplatin resistant and cisplatin delicate ovarian cancer cells .
In this post, we have examined regardless of whether metformin stimulates apoptosis furthermore to its anti proliferative action , therefore contributing to its anti neoplastic effect. Our flow cytometry benefits show that metformin induces apoptosis in each cell lines inside a dose dependent method . These findings were further confirmed by our effects displaying activation of caspase by metformin in each cell lines . Information concerning the impact of metformin on apoptosis in cancer cells reversible VEGFR inhibitor selleck chemicals are constrained and relatively inconsistent. Ben Sahra et al. have shown that metformin blocked the cell cycle from the G G phase in prostate cancer cells and did not induce apoptosis . Similarly, breast cancer cells did not undergo apoptosis in response to metformin .