In vitro induction of apoptosis in U937 cells by perillyl alcohol with sensitization by pentoxifylline: increased BCL-2 and BAX protein expression

Retinoblastoma: Review and new insights

Retinoblastoma (Rb), the most frequent malignant intraocular tumor in childhood, is caused by mutations in the retinoblastoma gene (RB1) situated on chromosome 13q14.2. The incidence of retinoblastoma is approximately 1 in 17,000 live births with approximately 8,000 new cases diagnosed each year worldwide. Rb is the prototypical hereditary cancer in humans. Autosomal dominant inheritance is seen in 30-40% of cases whereas the non-inherited sporadic type accounts for the remaining 60-70%. Rb arises due to inactivation of both alleles of the Rb tumor suppressor gene, which results in a defective Rb protein (pRB) with subsequent cell cycle impairment and uncontrolled cell proliferation. Patients with Rb have survival rates higher than 95-98% in industrialized countries but mortality remains high in developing countries. For example, the mortality rate in Africa is 70%. In all cases of intraocular and extraocular retinoblastoma, there is a need for new therapies that are more effective and carry less risk of toxicity. The Bruckner test is a practical and easy test for the detection of Rb, this test consists of assessing the fundus reflex through the pupil (red reflex) in both eyes simultaneously with a bright coaxial light produced with the direct ophthalmoscope. Rb can be detected by the Bruckner test showing a pupil that shines white or “Leukocoria”. Although the diagnosis of Rb remains essentially clinical, the newly identified biomarkers could contribute to early molecular detection, timely detection of micrometastases and establish new therapeutic options for Rb.

Perillyl alcohol for pediatric TP53- and RAS-mutated SHH-medulloblastoma: an in vitro and in vivo translational pre-clinical study

PURPOSE

Inhalation of perillyl alcohol (POH) recently emerged as an investigational promising antiglioma strategy. However, little attention has been paid to its therapeutic potential for other brain tumors, especially in the pediatric setting.

METHODS

The effects of POH were explored in medulloblastoma cell models belonging to the SHH variant with activation of RAS (ONS-76) or with TP53 mutations (DAOY and UW402), by means of proliferation and invasion assays. Interactions with methotrexate, thiotepa, or ionizing radiation were also assessed. Mice bearing subcutaneous tumors were treated with intraperitoneal injections. Alternatively, animals with intracranial tumors were exposed to intranasal POH alone or combined with radiation. Tumor growth was measured by bioluminescence. Analyses of cytotoxicity to the nasal cavity were also performed, and the presence of POH in the brain, lungs, and plasma was surveyed through chromatography/mass spectrometry.

RESULTS

POH decreased cell proliferation and colony formation, with conspicuous death, though the invasive capacity was only affected in the NRAS-mutated cell line. Median-drug effect analysis displayed synergistic combinations with methotrexate. Otherwise, POH showed to be a reasonable radiosensitizer. In vivo, intraperitoneal injection significantly decreased tumor volume. However, its inhalation did not affect orthotopic tumors, neither alone or followed by cranial irradiation. Nasal cavity epithelium showed unimportant alterations, though, no traces of POH or its metabolites were detected in tissue samples.

CONCLUSION

POH presents robust in vitro antimedulloblastoma effects and sensitizes cell lines to other conventional therapeutics, reducing tumor volume when administered intraperitoneally. Nevertheless, further improvement of delivery devices and/or drug formulations are needed to better characterize its effectiveness through inhalation.

Sensitizing the cytotoxic action of Docetaxel induced by Pentoxifylline in a PC3 prostate cancer cell line

BACKGROUND

Prostate cancer is one of the most frequently diagnosed types of cancers worldwide. In its initial period, the tumor is hormone-sensitive, but in advanced states, it evolves into a metastatic castration-resistant tumor. In this state, chemotherapy with taxanes such as Docetaxel (DTX) comprises the first line of treatment. However, the response is poor due to chemoresistance and toxicity. On the other hand, Pentoxifylline (PTX) is an unspecific inhibitor of phosphodiesterases; experimental, and clinically it has been described as sensitizing tumor cells to chemotherapy, increasing apoptosis and decreasing senescence. We study whether the PTX sensitizes prostate cancer cells to DTX for greater effectiveness.

METHODS

PC3 human prostate cancer cells were treated in vitro at different doses and times with PTX, DTX, or their combination. Viability was determined by the WST-1 assay by spectrophotometry, cell cycle progression, apoptosis, generic caspase activation and senescence by flow cytometry, DNA fragmentation and caspases-3, -8, and -9 activity by ELISA.

RESULTS

We found that PTX in PC3 human prostate cancer cells induces significant apoptosis per se and increases that generated by DTX, while at the same time it reduces the senescence caused by the chemotherapy and increases caspases-3,-8, and -9 activity in PTX + DTX-treated cells. Both treatments blocked the PC3 cell in the G1 phase.

CONCLUSIONS

Our results show that PTX sensitizes prostate tumor cells to apoptosis induced by DTX. Taken together, the results support the concept of chemotherapy with rational molecular bases.

Perillyl alcohol has antibacterial effects and reduces ROS production in macrophages

Natural products have emerged as a rich source of bioactive compounds for adjunctive treatments of many infectious and inflammatory conditions, including periodontitis. Among the monoterpenes with significant biological properties, there is the perillyl alcohol (POH), which can be found in several essential oils and has shown immunomodulatory properties in recent studies, which may be interesting in the treatment of non-neoplastic inflammatory disorders.

Pentoxifylline Enhances the Apoptotic Effect of Carboplatin in Y79 Retinoblastoma Cells

BACKGROUND/AIM

Retinoblastoma (RB) is the most common primary intraocular malignancy. Carboplatin (CPt) is a DNA damage-inducing agent that is widely used for the treatment of RB. Unfortunately, this drug also activates the transcription factor nuclear factor-kappa B (NF-ĸB), leading to promotion of tumor survival. Pentoxifylline (PTX) is a drug that inhibits the phosphorylation of I kappa B-alpha (IĸBα) in serines 32 and 36, and this disrupts NF-ĸB activity that promotes tumor survival. The goal of this study was to evaluate the effect of the PTX on the antitumor activity of CPt.

MATERIALS AND METHODS

Y79 RB cells were treated with CPt, PTX, or both. Cell viability, apoptosis, loss of mitochondrial membrane potential, the activity of caspase-9, -8, and -3, cytochrome c release, cell-cycle progression, p53, and phosphorylation of IĸBα, and pro- and anti-apoptotic genes were evaluated.

RESULTS

Both drugs significantly affected the viability of the Y79 RB cells in a time- and dose-dependent manner. The PTX+CPt combination exhibited the highest rate of apoptosis, a decrease in cell viability and significant caspase activation, as well as loss of mitochondrial membrane potential, release of cytochrome c, and increased p53 protein levels. Cells treated with PTX alone displayed decreased I kappa B-alpha phosphorylation, compared to the CPt treated group. In addition, the PTX+CPt combination treatment induced up-regulation of the proapoptotic genes Bax, Bad, Bak, and caspases- 3, -8, and -9, compared to the CPt and PTX individual treated groups.

CONCLUSION

PTX induces apoptosis per se and increases the CPt-induced apoptosis, augmenting its antitumor effectiveness.

Therapeutic targeting of replicative immortality

One of the hallmarks of malignant cell populations is the ability to undergo continuous proliferation. This property allows clonal lineages to acquire sequential aberrations that can fuel increasingly autonomous growth, invasiveness, and therapeutic resistance. Innate cellular mechanisms have evolved to regulate replicative potential as a hedge against malignant progression. When activated in the absence of normal terminal differentiation cues, these mechanisms can result in a state of persistent cytostasis. This state, termed “senescence,” can be triggered by intrinsic cellular processes such as telomere dysfunction and oncogene expression, and by exogenous factors such as DNA damaging agents or oxidative environments. Despite differences in upstream signaling, senescence often involves convergent interdependent activation of tumor suppressors p53 and p16/pRB, but can be induced, albeit with reduced sensitivity, when these suppressors are compromised. Doses of conventional genotoxic drugs required to achieve cancer cell senescence are often much lower than doses required to achieve outright cell death. Additional therapies, such as those targeting cyclin dependent kinases or components of the PI3K signaling pathway, may induce senescence specifically in cancer cells by circumventing defects in tumor suppressor pathways or exploiting cancer cells’ heightened requirements for telomerase. Such treatments sufficient to induce cancer cell senescence could provide increased patient survival with fewer and less severe side effects than conventional cytotoxic regimens. This positive aspect is countered by important caveats regarding senescence reversibility, genomic instability, and paracrine effects that may increase heterogeneity and adaptive resistance of surviving cancer cells. Nevertheless, agents that effectively disrupt replicative immortality will likely be valuable components of new combinatorial approaches to cancer therapy.

Vascular endothelium derived endothelin-1 is required for normal heart function after chronic pressure overload in mice

Background

Endothelin-1 participates in the pathophysiology of heart failure. The reasons for the lack of beneficial effect of endothelin antagonists in heart failure patients remain however speculative. The anti-apoptotic properties of ET-1 on cardiomyocytes could be a reasonable explanation. We therefore hypothesized that blocking the pro-apoptotic TNF-α pathway using pentoxifylline could prevent the deleterious effect of the lack of ET-1 in a model for heart failure.

Methods

We performed transaortic constriction (TAC) in vascular endothelial cells specific ET-1 deficient (VEETKO) and wild type (WT) mice (n = 5–9) and treated them with pentoxifylline for twelve weeks.

Results

TAC induced a cardiac hypertrophy in VEETKO and WT mice but a reduction of fractional shortening could be detected by echocardiography in VEETKO mice only. Cardiomyocyte diameter was significantly increased by TAC in VEETKO mice only. Pentoxifylline treatment prevented cardiac hypertrophy and reduction of fractional shortening in VEETKO mice but decreased fractional shortening in WT mice. Collagen deposition and number of apoptotic cells remained stable between the groups as did TNF-α, caspase-3 and caspase-8 messenger RNA expression levels. TAC surgery enhanced ANP, BNP and bcl2 expression. Pentoxifylline treatment reduced expression levels of BNP, bcl2 and bax.

Conclusions

Lack of endothelial ET-1 worsened the impact of TAC-induced pressure overload on cardiac function, indicating the crucial role of ET-1 for normal cardiac function under stress. Moreover, we put in light a TNF-α-independent beneficial effect of pentoxifylline in the VEETKO mice suggesting a therapeutic potential for pentoxifylline in a subpopulation of heart failure patients at higher risk.

Pentoxifylline and the proteasome inhibitor MG132 induce apoptosis in human leukemia U937 cells through a decrease in the expression of Bcl-2 and Bcl-XL and phosphorylation of p65

Background

In Oncology, the resistance of the cancerous cells to chemotherapy continues to be the principal limitation. The nuclear factor-kappa B (NF-κB) transcription factor plays an important role in tumor escape and resistance to chemotherapy and this factor regulates several pathways that promote tumor survival including some antiapoptotic proteins such as Bcl-2 and Bcl-XL. In this study, we investigated, in U937 human leukemia cells, the effects of PTX and the MG132 proteasome inhibitor, drugs that can disrupt the NF-κB pathway. For this, we evaluated viability, apoptosis, cell cycle, caspases-3, -8, -9, cytochrome c release, mitochondrial membrane potential loss, p65 phosphorylation, and the modification in the expression of pro- and antiapoptotic genes, and the Bcl-2 and Bcl-XL antiapoptotic proteins.

Results

The two drugs affect the viability of the leukemia cells in a time-dependent manner. The greatest percentage of apoptosis was obtained with a combination of the drugs; likewise, PTX and MG132 induce G1 phase cell cycle arrest and cleavage of caspases -3,-8, -9 and cytochrome c release and mitochondrial membrane potential loss in U937 human leukemia cells. In these cells, PTX and the MG132 proteasome inhibitor decrease p65 (NF-κB subunit) phosphorylation and the antiapoptotic proteins Bcl-2 and Bcl-XL. We also observed, with a combination of these drugs overexpression of a group of the proapoptotic genes BAX, DIABLO, and FAS while the genes BCL-XL, MCL-1, survivin, IκB, and P65 were downregulated.

Conclusions

The two drugs used induce apoptosis per se, this cytotoxicity was greater with combination of both drugs. These observations are related with the caspases -9, -3 cleavage and G1 phase cell cycle arrest, and a decrease in p65 phosphorylation and Bcl-2 and Bcl-XL proteins. As well as this combination of drugs promotes the upregulation of the proapoptotic genes and downregulation of antiapoptotic genes. These observations strongly confirm antileukemic potential.

Pentoxifylline sensitizes human cervical tumor cells to cisplatin-induced apoptosis by suppressing NF-kappa B and decreased cell senescence

BACKGROUND

Worldwide, cervical cancer is the second most common causes of cancer in women and represents an important mortality rate. Cisplatin (CIS) is a very important antitumoral agent and can lead tumor cells toward two important cellular states: apoptosis and senescence. In some types of cancers pentoxifylline (PTX) sensitizes these cells to the toxic action of chemotherapeutics drugs such as adriamycin, inducing apoptosis. In the present work, we studied in vitro whether PTX alone or in combination with CIS induces apoptosis and/or senescence in cervix cancer HeLa and SiHa cell lines infected with HPV types 16 and 18, respectively, as well as in immortalized keratinocytyes HaCaT cells.

METHODS

HeLa (HPV 18+), SiHa (HPV 16+) cervix cancer cells and non-tumorigenic immortalized HaCaT cells (control) were treated with PTX, CIS or both. The cellular toxicity and survival fraction of PTX and CIS were determinate by WST-1 and clonogenic assays respectively. Apoptosis, caspase activation and phosphorylation of ERK1/2, p38, p65 (NF-κB), Bcl-2 and Bcl-XL anti-apoptotic proteins were determinated by flow cytometry. Senescence by microscopy. Phosphorylation of IκBα and IκB total were measured by ELISA. Pro-apoptotic, anti-apoptotic and senescence genes, as well as HPV-E6/7 mRNA expression, were detected by RT-PCR.

RESULTS

Our results show that after 24 hours of incubation PTX per se is toxic for cancer cells affecting cell viability and inducing apoptosis. The toxicity in HaCaT cells was minimal. CIS induces apoptosis in HeLa and SiHa cells and its effect was significantly increases when the cells were treated with PTX + CIS. In all studies there was a direct correlation with levels of caspases (-3, -6, -7, -9 and -8) activity and apoptosis. CIS induces important levels of senescence and phosphorylation of ERK1/2, p38, p65/RELA, and IκBα, and decreased the expression of anti-apoptotic protein Bcl-XL. Surprisingly these levels were significantly reduced by PTX in tumor cells, and at the same time, increases the expression of pro-apoptotic genes.

CONCLUSION

PTX sensitizes cervical cancer cells to CIS-induced apoptosis and decreases the CIS-induced senescence in these cells via inhibition of NF-κB signaling pathway; diminishes expression of antiapoptotic proteins and the activation of caspases.

Sensitization of cervix cancer cells to Adriamycin by Pentoxifylline induces an increase in apoptosis and decrease senescence

Background

Chemotherapeutic drugs like Adriamycin (ADR) induces apoptosis or senescence in cancer cells but these cells often develop resistance and generate responses of short duration or complete failure. The methylxantine drug Pentoxifylline (PTX) used routinely in the clinics setting for circulatory diseases has been recently described to have antitumor properties. We evaluated whether pretreatment with PTX modifies apoptosis and senescence induced by ADR in cervix cancer cells.

Methods

HeLa (HPV 18+), SiHa (HPV 16+) cervix cancer cells and non-tumorigenic immortalized HaCaT cells (control) were treated with PTX, ADR or PTX + ADR. The cellular toxicity of PTX and survival fraction were determinated by WST-1 and clonogenic assay respectively. Apoptosis, caspase activation and ADR efflux rate were measured by flow cytometry, senescence by microscopy. IκBα and DNA fragmentation were determinated by ELISA. Proapoptotic, antiapoptotic and senescence genes, as well as HPV-E6/E7 mRNA expression, were detected by time real RT-PCR. p53 protein levels were assayed by Western blot.

Results

PTX is toxic (WST-1), affects survival (clonogenic assay) and induces apoptosis in cervix cancer cells. Additionally, the combination of this drug with ADR diminished the survival fraction and significantly increased apoptosis of HeLa and SiHa cervix cancer cells. Treatments were less effective in HaCaT cells. We found caspase participation in the induction of apoptosis by PTX, ADR or its combination. Surprisingly, in spite of the antitumor activity displayed by PTX, our results indicate that methylxantine, per se does not induce senescence; however it inhibits senescence induced by ADR and at the same time increases apoptosis. PTX elevates IκBα levels. Such sensitization is achieved through the up-regulation of proapoptotic factors such as caspase and bcl family gene expression. PTX and PTX + ADR also decrease E6 and E7 expression in SiHa cells, but not in HeLa cells. p53 was detected only in SiHa cells treated with ADR.

Conclusion

PTX is a good inducer of apoptosis but does not induce senescence. Furthermore, PTX reduced the ADR-induced senescence and increased apoptosis in cervix cancer cells.

Perillyl alcohol and methyl jasmonate sensitize cancer cells to cisplatin

Breast cancer is the second leading cause of cancer deaths among women in the United States. Several treatment options exist, with different side effects. To alleviate the side effects, several research groups have studied chemotherapeutic effects of plant compounds on cancer cells. These could be used as an alternative treatment option either alone or in combination with other chemotherapeutic drugs. The aim of this study was to evaluate the activity of a combination of perillyl alcohol (POH), methyl jasmonate (MJ) with cisplatin to define the most effective schedule and to investigate the mechanism of action in breast cancer cells. POH and MJ treatment (20% decrease in cell viability concentration) enhanced the cytotoxicity for subsequent exposure to cisplatin in MDA-MB-435 and MDA-MB-231 cells. Combination treatment of POH and MJ blocked cells at the G0/G1 phase of the cell cycle and the addition of cisplatin forced the cells to progress through the cell cycle and induced apoptosis. Apoptotic mechanistic studies indicated that POH and MJ treatment activated tumor necrosis factor receptor 1 and this was further increased by the addition of cisplatin. It was also found that mitochondrial membrane potential decreased with POH and MJ treatment; this effect was further enhanced by cisplatin treatment. These findings contributed to a better understanding of molecular mechanism of apoptosis in combination treatment of POH, MJ, and cisplatin. Results also showed that the combination treatment of three drugs is more effective than single drug alone or two drugs together.

Perillyl Alcohol Protects Against Fe-NTA-Induced Nephrotoxicity and Early Tumor Promotional Events in Rat Experimental Model

Plants have been widely used as protective agents against a wide variety of processes and compounds that damage tissues via free radical mechanisms. Perillyl alcohol (PA) is a naturally occurring monoterpene found in the essential oils of numerous species of plants including mints, cherries and celery seeds. This monocyclic monoterpene has shown antioxidant and therapeutic activity in various studies against various xenobiotics. In this study, we have analyzed the effects of PA against single intraperitoneal dose of ferric nitrilotriacetate (Fe-NTA) (9 mg iron per kg body weight)-induced nephrotoxicity and early tumor promotional events. The pretreatment of Fe-NTA-treated rats with 0.5% per kg body weight dose and 1% per kg body weight dose of PA for seven consecutive days significantly reversed the Fe-NTA-induced malondialdehyde formation, xanthine oxidase activity (P < 0.001), ornithine decarboxylase activity (P < 0.001) and (3)[H]thymidine incorporation in renal DNA (P < 0.001) with simultaneous significant depletion in serum toxicity markers blood urea nitrogen and creatinine (P < 0.001). Significant restoration at both the doses was recorded in depleted renal glutathione content, and its dependent enzymes with prophylactic treatment of PA. Present results suggest that PA potentially attenuates against Fe-NTA-induced oxidative damage and tumor promotional events that preclude its development as a future drug to avert the free radical-induced toxicity.

Phase II trial of daily oral perillyl alcohol (NSC 641066) in treatment-refractory metastatic breast cancer

PURPOSE

Perillyl alcohol (POH) is a naturally occurring lipid with preclinical activity against mammary carcinomas. We conducted a phase II multi-institutional study of oral POH administered four times daily in women with advanced treatment-refractory breast cancer.

METHODS

Eligible women were treated with POH four times daily at 1,200-1,500 mg m(-2) dose(-1) on a 28-day cycle. Patients tolerating 1,200 mg m(-2) day(-1) four times daily after one cycle were dose-escalated to 1,500 mg/m(2). The primary endpoint was 1-year freedom-from-progression (FFP) rate. Secondary endpoints were response rate, tolerability and correlative evaluations.

RESULTS

Twenty-nine cycles of POH were administered to 14 women. Three patients were dose-escalated to 1,500 mg/m(2). Grade 1 and grade 2 gastrointestinal effects and fatigue were predominant toxicities. Of seven patients receiving up to one cycle, three stopped therapy due to intolerance. Only two patients received more than two cycles, with disease stabilization of 3 and 8 months. Thirteen patients were evaluable for response. One-year FFP rate was zero. No objective responses were seen. The median time to progression was 35 days (95% CI, 29-123 days). Median overall survival was 389 days (95% CI, 202-776 days). Pharmacokinetic parameters were similar to previous investigations. The ability to correlate plasma TGF-beta1 levels with outcome was limited by lack of clinical benefit and inter- and intra-patient variability.

CONCLUSIONS

Enrollment was suspended short of planned accrual because of lack of response and poor tolerance to POH. This regimen does not appear to provide benefit in advanced treatment-refractory breast carcinoma.