CD4+FOXP3+ regulatory T cell depletion by low-dose cyclophosphamide prevents recurrence in patients with large condylomata acuminata after laser therapy

The expression and significance of PD-L1 in condyloma acuminatum

BACKGROUND

It has been reported that programmed death-ligand 1 (PD-L1) is highly expressed in cells during viral infection, which helps the virus escape host immunity. However, the relationship between human papillomavirus (HPV) and PD-L1 in condyloma acuminatum and whether they participate in immunosuppression have not been reported. In this paper, we aimed to explore the expression and significance of PD-L1 in condyloma acuminatum.

METHODS

The expression of PD-L1 in the wart of condyloma acuminatum patients and the foreskin of healthy individuals was evaluated. Lentivirus transfection was used to introduce the HPV11-E7 gene into HaCaT cells to investigate whether HPV infection could affect the expression of PD-L1. The successfully constructed HPV11-E7 HaCaT cells were cocultured with Jurkat cells, and Jurkat cell apoptosis and proliferation as well as the Jurkat cell cycle were evaluated by flow cytometry and cell counting kit-8 (CCK-8) assays.

RESULTS

PD-L1 was highly expressed in keratinocytes of genital warts. Through the construction of a cell model, we found that HPV11-E7 could upregulate the expression of PD-L1 in HaCaT cells. Furthermore, HPV11-E7 HaCaT cells can promote the apoptosis of Jurkat cells, inhibit the proliferation of Jurkat cells and mediate the cell cycle arrest of Jurkat cells through the PD-1/PD-L1 signalling pathway.

CONCLUSIONS

HPV infection may upregulate PD-L1 expression in the keratinocytes of genital warts and participate in the inhibition of local T-cell function.

Repurposing Food and Drug Administration-Approved Drugs to Promote Antitumor Immunity

There has been a major resurgence of interest in immune-based approaches to treat cancer, based largely on the success of checkpoint inhibitors (anti-cytotoxic T-lymphocyte-associated antigen 4, anti-programmed cell death 1, and anti-programmed cell death ligand 1 antibodies) in several malignancies. However, not all tumors respond to checkpoint therapy, and there is clearly a need for additional approaches for enhancing tumor immunity. We summarize the critical elements necessary for mounting an efficacious T-cell response to a tumor. We cite drugs approved by the Food and Drug Administration for no-cancer indications that could be repurposed and used as part of an antitumor immune cocktail. We also list cancer drugs not initially intended to impact tumor immunity (soft repurposing) but that have been found to modulate the immune system. We highlight those drugs that might be used in combination with checkpoint inhibitors to increase response rates and survival of cancer patients. Our focus will be on drugs for which there are limited but existing human data. We cite supporting mechanistic mouse data as well. Repurposing drugs to modulate antitumor immunity is an opportunity to rapidly bring new, effective, and affordable treatments to cancer patients.

Enhanced Glycogen Metabolism Supports the Survival and Proliferation of HPV-Infected Keratinocytes in Condylomata Acuminata

Condylomata acuminata (CA) is caused by human papillomavirus (HPV) infections of keratinocytes and is a common sexually transmitted disease. The main clinical feature and risk of CA is the high recurrence of genital warts formed by infected keratinocytes. Metabolic reprogramming of most types of mammalian cells including keratinocytes can provide energy and intermediates essential for their survival. Here, we report that HPV infection develops a hypoxic microenvironment in CA warts by inducing the accumulation of glycogen and increased glycogen metabolism in the infected keratinocytes in a hypoxia-inducible factor 1α (HIF-1α) -dependent pathway. Our in vitro studies show that the increased glycogen metabolism is essential for the survival and proliferation of keratinocytes. Regarding its mechanism of action, glycogenolysis generates glucose-1-phosphate that fluxes into the pentose phosphate pathway and, then, generates abundant nicotinamide adenine dinucleotide phosphate, thereby ensuring high levels of glutathione in keratinocytes under hypoxia. The abrogation of glycogen synthesis and glycogenolysis decreases the ratio of glutathione and glutathione disulfide and increases the level of ROS, further resulting in the impairment of keratinocyte survival. Collectively, our work offers an insight into the metabolic reprogramming in the development of CA and implies that the intervention of glycogen metabolism would be a promising therapeutic target for CA.

Treatment of Metastatic or High-Risk Solid Cancer Patients by Targeting the Immune System and/or Tumor Burden: Six Cases Reports

This article summarizes the histories of six patients with different solid tumors treated with a new strategy based on tumor burden reduction and immune evasion as potential targets. All six patients were at a high risk of relapse and were likely to have a minimal residual disease following conventional therapy: biochemical recurrence (BCR) following radical prostatectomy (RP) (two prostate cancers patients), removal of distant metastases (one colorectal and one breast cancer), and complete response (CR) of distant metastases to conventional therapy (one breast cancer and one esophageal–gastric junction cancer). Four of the patients, two after RP and BCR, one after removal of a single pulmonary metastasis from breast cancer, and one after CR to chemotherapy of peritoneal metastases and ascites from an esophageal–gastric junction primary cancer, regularly received cycles of a new drug schedule with the aim of inhibiting immune suppression (IT). In these four patients, preliminary laboratory tests of peripheral blood suggested an interleukin (IL)-2/IL-12 mediated stimulation of cellular immune response with a concomitant decrease in vascular endothelial growth factor (VEGF) immune suppression. The fifth case was a breast cancer patient with distant metastases in CR, while receiving beta-interferon and interleukin-2 in addition to conventional hormone therapy. To date, all five patients are alive and doing well and they have been unexpectedly disease-free for 201 and 78 months following BCR, 28 months following the removal of a single pulmonary metastases, 32 months following CR to chemotherapy of peritoneal metastases and ascites, and 140 months following diagnosis of multiple bone metastases, respectively. The sixth patient, who had colorectal cancer and multiple synchronous liver metastases and underwent nine surgical interventions for metastatic disease, although not disease-free, is doing well 98 months after primary surgery. Our six cases reports can be interpreted with the hypothesis that immune manipulation and/or a concomitant low tumor burden favored their clinical outcome.

Advances in Designing and Developing Vaccines, Drugs and Therapeutic Approaches to Counter Human Papilloma Virus

Human papillomavirus (HPV) is a viral infection with skin-to-skin based transmission mode. HPV annually caused over 500,000 cancer cases including cervical, anogenital and oropharyngeal cancer among others. HPV vaccination has become a public-health concern, worldwide, to prevent the cases of HPV infections including precancerous lesions, cervical cancers, and genital warts especially in adolescent female and male population by launching national programs with international alliances. Currently, available prophylactic and therapeutic vaccines are expensive to be used in developing countries for vaccination programs. The recent progress in immunotherapy, biotechnology, recombinant DNA technology and molecular biology along with alternative and complementary medicinal systems have paved novel ways and valuable opportunities to design and develop effective prophylactic and therapeutic vaccines, drugs and treatment approach to counter HPV effectively. Exploration and more researches on such advances could result in the gradual reduction in the incidences of HPV cases across the world. The present review presents a current global scenario and futuristic prospects of the advanced prophylactic and therapeutic approaches against HPV along with recent patents coverage of the progress and advances in drugs, vaccines and therapeutic regimens to effectively combat HPV infections and its cancerous conditions.

Efficacy of fulguration combined with imiquimod cream on condyloma acuminatum, and the effect on immune functions and serums levels of IL-2 and IL-10

The objective of the present study was to investigate the clinical efficacy of high-frequency fulguration combined with 5% imiquimod cream for condyloma acuminatum (CA), and the effect on T cell immune function and serum levels of interleukin (IL)-2 and IL-10. We enrolled 112 patients with CA between January 2014 and January 2016. Patients were randomly divided into the control group (n=56) and observation group (n=56). The control group received high-frequency fulguration combined with intramuscular injection of Bacillus Calmette-Guérin polysaccharide nucleic acid, and the observation group received high-frequency fulguration combined with external application of 5% imiquimod cream. In both groups, the course of treatment lasted for 12 weeks, and the follow-up period was 6 months. Clinical efficacy was compared between the groups. The total effective rate in the observation group was higher than that in the control group (p<0.05), but no significant differences were identified in comparisons of effectiveness and recurrence rate between the two groups (p>0.05). After treatment, the levels of CD3⁺ and CD4⁺ cells, and CD4⁺/CD8⁺ ratio in both groups were increased compared with those before treatment (p<0.05), while no significant difference was identified in comparison of the levels of CD8⁺ cells in both groups before and after treatment (p>0.05); in both groups before and after treatment, there was no significant difference in the comparison of T cells (p>0.05). After treatment in both groups, the serum levels of IL-2 were increased, and the levels of IL-10 were decreased compared with those before treatment; the improvement in the observation group was superior to that in the control group (p<0.05). In conclusion, good efficacy can be achieved with the combined treatment of high-frequency fulguration and 5% imiquimod cream for CA, which is correlated with enhanced immune functions of T cells, and improvements in the serum levels of IL-2 and IL-10.

The effect of cyclophosphamide on the immune system: implications for clinical cancer therapy

Cyclophosphamide is an alkylating agent belonging to the group of oxazaphosporines. As cyclophosphamide is in clinical use for more than 40 years, there is a lot of experience using this drug for the treatment of cancer and as an immunosuppressive agent for the treatment of autoimmune and immune-mediated diseases. Besides antimitotic and antireplicative effects, cyclophosphamide has immunosuppressive as well as immunomodulatory properties. Cyclophosphamide shows selectivity for T cells and is therefore now frequently used in tumour vaccination protocols and to control post-transplant allo-reactivity in haplo-identical unmanipulated bone marrow after transplantation. The schedule of administration is of special importance for the immunological effect: while cyclophosphamide can be used in high-dose therapy for the complete eradication of haematopoietic cells, lower doses of cyclophosphamide are relatively selective for T cells. Of special interest is the fact that a single administration of low-dose cyclophosphamide is able to selectively suppress regulatory T cells (Tregs). This effect can be used to counteract immunosuppression in cancer. However, cyclophosphamide can also increase the number of myeloid-derived suppressor cells. Combination of cyclophosphamide with other immunomodulatory agents could be a promising approach to treat different forms of advanced cancer.

Immune Dysregulation in Patients Persistently Infected with Human Papillomaviruses 6 and 11

Human Papillomaviruses (HPVs) 6 and 11 are part of a large family of small DNA viruses, some of which are commensal. Although much of the population can contain or clear infection with these viruses, there is a subset of individuals who develop persistent infection that can cause significant morbidity and on occasion mortality. Depending on the site of infection, patients chronically infected with these viruses develop either recurrent, and on occasion, severe genital warts or recurrent respiratory papillomas that can obstruct the upper airway. The HPV-induced diseases described are likely the result of a complex and localized immune suppressive milieu that is characteristic of patients with persistent HPV infection. We review data that documents impaired Langerhans cell responses and maturation, describes the polarized adaptive T-cell immune responses made to these viruses, and the expression of class select II MHC and KIR genes that associate with severe HPV6 and 11 induced disease. Finally, we review evidence that documents the polarization of functional T_H2 and T-regulatory T-cells in tissues persistently infected with HPV6 and 11, and we review evidence that there is suppression of natural killer cell function. Together, these altered innate and adaptive immune responses contribute to the cellular and humoral microenvironment that supports HPV 6 and 11-induced disease.

Immunologic treatments for precancerous lesions and uterine cervical cancer

Development of HPV-associated cancers not only depends on efficient negative regulation of cell cycle control that supports the accumulation of genetic damage, but also relies on immune evasion that enable the virus to go undetected for long periods of time. In this way, HPV-related tumors usually present MHC class I down-regulation, impaired antigen-processing ability, avoidance of T-cell mediated killing, increased immunosuppression due to Treg infiltration and secrete immunosuppressive cytokines. Thus, these are the main obstacles that immunotherapy has to face in the treatment of HPV-related pathologies where a number of different strategies have been developed to overcome them including new adjuvants. Although antigen-specific immunotherapy induced by therapeutic HPV vaccines was proved extremely efficacious in pre-clinical models, its progression through clinical trials suffered poor responses in the initial trials. Later attempts seem to have been more promising, particularly against the well-defined precursors of cervical, anal or vulvar cancer, where the local immunosuppressive milieu is less active. This review focuses on the advances made in these fields, highlighting several new technologies (such as mRNA vaccine, plant-derived vaccine). The most promising immunotherapies used in clinical trials are also summarized, along with integrated strategies, particularly promising in controlling tumor metastasis and in eliminating cancer cells altogether.

After the early promising clinical results, the development of therapeutic HPV vaccines need to be implemented and applied to the users in order to eradicate HPV-associated malignancies, eradicating existing perception (after the effectiveness of commercial preventive vaccines) that we have already solved the problem.

Antitumor and immunomodulatory effects of low-dose 5-FU on hepatoma 22 tumor-bearing mice

Low-dose 5-fluorouracil (5-FU), a widely used chemotherapeutic, has been reported to have immunomodulatory effects. This study aimed to evaluate the optimal dose of 5-FU that produces antitumor and immunomodulatory effects. In a hepatoma 22 tumor-bearing mouse model, 0, 10, 20 and 40 mg/kg 5-FU (i.p.) was administered for 10 days. Tumor weight and volume were measured, thymus index (TI) and spleen index (SI) were calculated, and the number of white blood cells (WBCs) and lymphocytes (LYs) were counted following treatment. The percentages of CD3⁺, CD4⁺, CD8⁺ and natural killer (NK) cells were measured by flow cytometry. In addition, the body weights of the mice were measured and the average diet consumption was calculated. Administration of 5-FU produced a potent antitumor effect in a dose-dependent manner (P<0.01). At 20 and 40 mg/kg, a significant reduction of body weight and food consumption was observed. TI and SI decreased in the 20- and 40-mg/kg groups (P<0.01) for 10 days. The number of WBCs significantly decreased in each group (P<0.01); however, the number of LYs only decreased in the 40-mg/kg group (P<0.01). Percentages of CD3⁺ and CD4⁺ cells were increased in the 10- and 20-mg/kg groups (P<0.01). Thus, 5-FU at 10 mg/kg inhibits tumor growth while maintaining the immune function of the mice. 5-FU may exert its antitumor effect at a low dose with low toxicity and stimulate the host immune system. Future clinical trials taking into account the immunostimulatory capacity of chemotherapeutic agents are desirable for certain patients.

Combined use of cyclophosphamide and Chalone 19-peptide in experimental breast cancer

Background

Cyclophosphamide is a potent anticancer drug, but its clinical utility is limited because of its severe side effects, in particular liver damage. Chalone 19-peptide induces apoptosis of tumor cells and inhibits tumor growth. The present study investigated the antitumor effects of a combination of cyclophosphamide and Chalone 19-peptide in experimental breast cancer.

Methods

An animal model of breast cancer was developed, consisting of an MDA-MB-231 cell line implanted in the nude mouse. Eight doses of a combination of cyclophosphamide 50 mg/kg or 100 mg/kg and Chalone 19-peptide 6.6 mg/kg were administered, and the mice were euthanized 28 days after the final drug injection. Histopathologic analysis of tumor size, metastasis, and apoptosis of cancer cells was performed. Control mice were injected intraperitoneally with either cyclophosphamide alone or the same volume of solvent.

Results

Tumor sizes in the treatment groups were smaller than in the controls. No metastasis was found in the groups treated with cyclophosphamide and Chalone 19-peptide, but lung metastasis was found in controls. Liver damage in the groups treated with cyclophosphamide was more serious than in the other groups.

Conclusion

Addition of Chalone 19-peptide can improve the ability of cyclophosphamide to inhibit tumor growth and also reduces side effects.

Immunotherapy against HPV16/18 generates potent TH1 and cytotoxic cellular immune responses

Despite the development of highly effective prophylactic vaccines against human papillomavirus (HPV) serotypes 16 and 18, prevention of cervical dysplasia and cancer in women infected with high-risk HPV serotypes remains an unmet medical need. We report encouraging phase 1 safety, tolerability, and immunogenicity results for a therapeutic HPV16/18 candidate vaccine, VGX-3100, delivered by in vivo electroporation (EP). Eighteen women previously treated for cervical intraepithelial neoplasia grade 2 or 3 (CIN2/3) received a three-dose (intramuscular) regimen of highly engineered plasmid DNA encoding HPV16 and HPV18 E6/E7 antigens followed by EP in a dose escalation study (0.3, 1, and 3 mg per plasmid). Immunization was well tolerated with reports of mild injection site reactions and no study-related serious or grade 3 and 4 adverse events. No dose-limiting toxicity was noted, and pain was assessed by visual analog scale, with average scores decreasing from 6.2/10 to 1.4 within 10 min. Average peak interferon-γ enzyme-linked immunospot magnitudes were highest in the 3 mg cohort in comparison to the 0.3 and 1 mg cohorts, suggesting a trend toward a dose effect. Flow cytometric analysis revealed the induction of HPV-specific CD8(+) T cells that efficiently loaded granzyme B and perforin and exhibited full cytolytic functionality in all cohorts. These data indicate that VGX-3100 is capable of driving robust immune responses to antigens from high-risk HPV serotypes and could contribute to elimination of HPV-infected cells and subsequent regression of the dysplastic process.

CD4+Foxp3+ regulatory T cells prolong drug-induced disease remission in (NZBxNZW) F1 lupus mice

Introduction

The ability to ameliorate murine lupus renders regulatory T cells (Treg) a promising tool for the treatment of systemic lupus erythematosus (SLE). In consideration to the clinical translation of a Treg-based immunotherapy of SLE, we explored the potential of CD4+Foxp3+ Treg to maintain disease remission after induction of remission with an established cyclophosphamide (CTX) regimen in lupus-prone (NZBxNZW) F1 mice. As a prerequisite for this combined therapy, we also investigated the impact of CTX on the biology of endogenous Treg and conventional CD4+ T cells (Tcon).

Methods

Remission of disease was induced in diseased (NZBxNZW) F1 mice with an established CTX regimen consisting of a single dose of glucocorticosteroids followed by five day course with daily injections of CTX. Five days after the last CTX injection, differing amounts of purified CD4+Foxp3+CD25+ Treg were adoptively transferred and clinical parameters, autoantibody titers, the survival and changes in peripheral blood lymphocyte subsets were determined at different time points during the study. The influence of CTX on the numbers, frequencies and proliferation of endogenous Treg and Tcon was analyzed in lymphoid organs by flow cytometry.

Results

Apart from abrogating the proliferation of Tcon, we found that treatment with CTX induced also a significant inhibition of Treg proliferation and a decline in Treg numbers in lymphoid organs. Additional adoptive transfer of 1.5 × 10⁶ purified Treg after the CTX regimen significantly increased the survival and prolonged the interval of remission by approximately five weeks compared to mice that received only the CTX regimen. The additional clinical amelioration was associated with an increase in the Treg frequency in the peripheral blood indicating a compensation of CTX-induced Treg deficiency by the Treg transfer.

Conclusions

Treg were capable to prolong the interval of remission induced by conventional cytostatic drugs. This study provides valuable information and a first proof-of-concept for the feasibility of a Treg-based immunotherapy in the maintenance of disease remission in SLE.

T-cell activation by treatment of cancer patients with EMD 521873 (Selectikine), an IL-2/anti-DNA fusion protein

Background

EMD 521873 (Selectikine or NHS-IL2LT) is a fusion protein consisting of modified human IL-2 which binds specifically to the high-affinity IL-2 receptor, and an antibody specific for both single- and double-stranded DNA, designed to facilitate the enrichment of IL-2 in tumor tissue.

Methods

An extensive analysis of pharmacodynamic (PD) markers associated with target modulation was assessed during a first-in-human phase I dose-escalation trial of Selectikine.

Results

Thirty-nine patients with metastatic or locally advanced tumors refractory to standard treatments were treated with increasing doses of Selectikine, and nine further patients received additional cyclophosphamide. PD analysis, assessed during the first two treatment cycles, revealed strong activation of both CD4⁺ and CD8⁺ T-cells and only weak NK cell activation. No dose response was observed. As expected, Treg cells responded actively to Selectikine but remained at lower frequency than effector CD4⁺ T-cells. Interestingly, patient survival correlated positively with both high lymphocyte counts and low levels of activated CD8⁺ T-cells at baseline, the latter of which was associated with enhanced T-cell responses to the treatment.

Conclusions

The results confirm the selectivity of Selectikine with predominant T-cell and low NK cell activation, supporting follow-up studies assessing the clinical efficacy of Selectikine for cancer patients.

Therapy of human papillomavirus-related disease

This chapter reviews the current treatment of chronic and neoplastic human papillomavirus (HPV)-associated conditions and the development of novel therapeutic approaches. Surgical excision of HPV-associated lower genital tract neoplasia is very successful but largely depends on secondary prevention programmes for identification of disease. Only high-risk HPV-driven chronic, pre-neoplastic lesions and some very early cancers cannot be successfully treated by surgical procedures alone. Chemoradiation therapy of cervical cancer contributes to the 66-79% cervical cancer survival at 5 years. Outlook for those patients with persistent or recurrent cervical cancer following treatment is very poor. Topical agents such as imiquimod (immune response modifier), cidofovir (inhibition of viral replication; induction apoptosis) or photodynamic therapy (direct damage of tumour and augmentation of anti-tumour immunity) have all shown some useful efficacy (~50-60%) in treatment of high grade vulvar intraepithelial neoplasia (VIN). Provider administered treatments of genital warts include cryotherapy, trichloracetic acid, or surgical removal which has the highest primary clearance rate. Patient applied therapies include podophyllotoxin and imiquimod. Recurrence after "successful" treatment is 30-40%. Further improvements could derive from a rational combination of current therapy with new drugs targeting molecular pathways mediated by HPV in cancer. Small molecule inhibitors targeting the DNA binding activities of HPV E1/E2 or the anti-apoptotic consequences of E6/E7 oncogenes are in preclinical development. Proteasome and histone deacetylase inhibitors, which can enhance apoptosis in HPV positive tumour cells, are being tested in early clinical trials. Chronic high-risk HPV infection/neoplasia is characterised by systemic and/or local immune suppressive regulatory or escape factors. Recently two E6/E7 vaccines have shown some clinical efficacy in high grade VIN patients and this correlated with strong and broad systemic HPV-specific T cell response and modulation of key local immune factors. Treatments that can shift the balance of immune effectors locally in combination with vaccination are now being tested. This article forms part of a special supplement entitled "Comprehensive Control of HPV Infections and Related Diseases" Vaccine Volume 30, Supplement 5, 2012.

Cyclic adenosine monophosphate involvement in low-dose cyclophosphamide-reversed immune evasion in a mouse lymphoma model

Lymphoma cells mobilize many mechanisms to evade the immune system. There is substantial evidence that CD4(+)CD25(+) regulatory T cells (Tregs) play a key role in the control of immune evasion. Tregs can transfer cyclic adenosine monophosphate (cAMP) to effector T cells, suggesting an association between Tregs' immune-evasion role and the intracellular cAMP pathway. In this study, we used A20 B-cell lymphoma mice as aggressive tumor models to investigate the mechanism of the depletion of Tregs by low-dose cyclophosphamide (CY, 20 mg/kg). The tumor-bearing mice had longer survival times and slower tumor growth rates following treatment with CY, but its effects were temporary. Along with the depletion of Tregs by low-dose CY treatment, the expression of interleukin-2 (IL-2) in T effector cells increased, and intracellular cAMP concentrations in immune cells decreased. Our study demonstrates the ability of low-dose CY to reverse Tregs-mediated immune evasion in a mouse model. The changes in intracellular cAMP concentrations correlated with the upregulation of effector T cells and the downregulation of Tregs, indicating the close association of cAMP analogs and low-dose CY in the immune therapy of B-cell lymphoma.

Genital human papillomavirus infections: current and prospective therapies

Infection with human papillomaviruses (HPVs) is very common and associated with benign and malignant epithelial proliferations of skin and internal squamous mucosae. A subset of the mucosal HPVs are oncogenic and associated with 5 % of all cancers in men and women. There are two licensed prophylactic vaccines, both target HPV 16 and 18, the two most pathogenic, oncogenic types and one, additionally, targets HPV 6 and 11 the cause of genital warts. The approach of deliberate immunization with oncogenic HPV E6 and/or E7 proteins and the generation of antigen-specific cytotoxic T-cells as an immunotherapy for HPV-associated cancer and their high-grade pre-cancers has been tested with a wide array of potential vaccine delivery systems in Phase I/II trials with varying success. Understanding local viral and tumour immune evasion strategies is a prerequisite for the rational design of therapeutic vaccines for HPV-associated infection and disease, progress in this is discussed. There are no antiviral drugs for the treatment of HPV infection and disease. Current therapies are not targeted antiviral therapies, but either attempt physical removal of the lesion or induce inflammation and a bystander immune response. There has been recent progress in the identification and characterization of molecular targets for small molecule antagonists of the HPV proteins E1, E2 and E6 or their interactions with their cellular targets. Lead compounds that could disrupt E1-E2 protein-protein interactions have been discovered as have inhibitors of E6-E6-AP-binding interactions. Some of these compounds showed nanomolar affinities and high specificities and demonstrate the feasibility of this approach for HPV infections. These studies are, however, at an early phase and it is unlikely that any specific anti-HPV chemotherapeutic will be in the clinic within the next 10-20 years.

New Approaches to Immunotherapy for HPV Associated Cancers

Cervical cancer is the second most common cancer of women worldwide and is the first cancer shown to be entirely induced by a virus, the human papillomavirus (HPV, major oncogenic genotypes HPV-16 and -18). Two recently developed prophylactic cervical cancer vaccines, using virus-like particles (VLP) technology, have the potential to prevent a large proportion of cervical cancer associated with HPV infection and to ensure long-term protection. However, prophylactic HPV vaccines do not have therapeutic effects against pre-existing HPV infections and do not prevent their progression to HPV-associated malignancy. In animal models, therapeutic vaccines for persisting HPV infection can eliminate transplantable tumors expressing HPV antigens, but are of limited efficacy in inducing rejection of skin grafts expressing the same antigens. In humans, clinical trials have reported successful immunotherapy of HPV lesions, providing hope and further interest. This review discusses possible new approaches to immunotherapy for HPV associated cancer, based on recent advances in our knowledge of the immunobiology of HPV infection, of epithelial immunology and of immunoregulation, with a brief overview on previous and current HPV vaccine clinical trials.

Regulatory T cells in gastrointestinal tumors

Regulatory T cells (Tregs) have the ability to suppress the activity of most other lymphoid cells, as well as dendritic cells through cell-cell contact-dependent mechanisms, which have not yet been fully defined. Tregs are a key component of a functional immune system and Treg deficiency is associated with severe autoimmunity and allergies. However, Tregs specific for tumor-associated antigens are present in cancer patients and Tregs accumulate in many types of solid tumors, where they probably act to promote tumor escape from cytotoxic immune responses. Indeed, some studies even show a negative correlation between Treg infiltration and survival of the patient. Several studies indicate an active recruitment of Tregs to the tumor site and the mechanisms of Treg accumulation are starting to be better understood as a result of more detailed analysis of their adhesion molecule and chemokine receptor expression. In addition, in gastrointestinal tumors there is an increase in tumor-associated Tregs, but intriguingly, Treg infiltration into colorectal adenocarcinomas is associated with improved prognosis. In this article, we will review the proposed mechanisms of immune suppression by tumor-associated Tregs, how the tumor microenvironment favors immune evasion and Treg induction, the tumor-homing mechanisms of Tregs and how Tregs affect progression of gastric and colorectal tumors.

Efficient Treg depletion induces T-cell infiltration and rejection of large tumors

There are a number of factors that hamper immunotherapy of cancer. For example, tumors exhibit an aberrant vasculature that appears to form a barrier against T-cell infiltration. Another major obstacle is created by Treg. So far, conventional depletion of Treg with anti-CD25 antibodies, which eliminate only 70% of Treg, has failed to significantly reduce the growth of established tumors. Using Foxp3.LuciDTR-4 mice, we show here that 90-95% Treg depletion resulted in complete regression of large established tumors, whereas 70% depletion was ineffective. The extensive Treg depletion induced a number of processes that are critical for tumor rejection, including activation of tumor-specific CD8(+) T cells and enhanced infiltration of these cells into the tumor. The precise mechanism of enhanced infiltration is not known, but normalization of the tumor vasculature is assumed to assist infiltration. Indeed, we observed that 90% Treg depletion caused normalization of the tumor vasculature as indicated by a reduction in leakiness and the number of dilated vessels. These results suggest that for clinical immunotherapy of cancer, it would be desirable to have reagents that allow high-level depletion of Treg, which, in conjunction with treatment modalities such as vaccination, may concomitantly increase T-cell activation and infiltration.

Low dosages: new chemotherapeutic weapons on the battlefield of immune-related disease

Chemotherapeutic drugs eliminate tumor cells at relatively high doses and are considered weapons against tumors in clinics and hospitals. However, despite their ability to induce cellular apoptosis, chemotherapeutic drugs should probably be regarded more as a class of cell regulators than cell killers, if the dosage used and the fact that their targets are involved in basic molecular events are considered. Unfortunately, the regulatory properties of chemotherapeutic drugs are usually hidden or masked by the massive cell death induced by high doses. Recent evidence has begun to suggest that low dosages of chemotherapeutic drugs might profoundly regulate various intracellular aspects of normal cells, especially immune cells. Here, we discuss the immune regulatory roles of three kinds of chemotherapeutic drugs under low-dose conditions and propose low dosages as potential new chemotherapeutic weapons on the battlefield of immune-related disease.

Successful strategies for increasing African American participation in cancer genetic studies: hopeful signs for equalizing the benefits of genetic medicine

OBJECTIVE

To determine whether prior success in recruiting African Americans to an in-house cancer genetics registry could be duplicated when recruiting to a national registry requiring a significantly increased level of commitment. Additionally, to determine which recruitment sources and practices yielded the highest number of African American participants.

METHODS

A retrospective analysis of recruitment sources, practices, and results for recruitment to the Cancer Genetics Network (CGN; a national research registry), from 2000 to 2005 was conducted. These results were compared to previous experience in recruiting African Americans to the Family Cancer Registry (FCR; an in-house registry) during the period 1992-2005.

RESULTS

In the 1st year of recruitment to the CGN, African Americans accounted for 24% of those consenting to participate in the CGN registry from our center. This compares to an average annual rate of 27% for the FCR during the years 1998-2005, and a rate of less than 1% from 1992 to 1998. By 2005, African Americans accounted for 27% of CGN participants recruited through the University of Texas Southwestern Medical Center, one of eighteen participating institutions in the CGN. Hospital-based resources such as cancer treatment clinics and tumor registries yielded the highest percentage of African American participants (66.5%), and self-referral yielded the lowest (0%). Seventy-seven percent of African Americans were actively sought out and recruited from treatment clinics, whereas the vast majority of Caucasian participants were recruited passively during the course of genetic counseling sessions that were scheduled for reasons unrelated to participation in cancer research. There were no known instances of African Americans contacting CGN staff after reading printed recruitment materials or internet advertisements.

CONCLUSIONS

The increased level of commitment required of CGN participants did not deter African Americans from participating in cancer genetics research. Recruitment strategies responsible for dramatically increasing recruitment rates to the FCR from 1998 to 2000 were equally effective when used for recruitment to the CGN. The most effective recruitment sources were high-yield venues such as cancer treatment clinics and tumor registries, and active recruitment methods yielded the highest number of African American participants. Advertising through internet announcements and printed recruitment materials did not appear to be effective.