Human immunodeficiency virus protease inhibitors reduce the growth of human tumors via a proteasome-independent block of angiogenesis and matrix metalloproteinases

Inhibition of human DNA alkylation damage repair enzyme ALKBH2 by HIV protease inhibitor ritonavir

The human DNA repair enzyme AlkB homologue-2 (ALKBH2) repairs methyl adducts from genomic DNA and is overexpressed in several cancers. However, there are no known inhibitors available for this crucial DNA repair enzyme. The aim of this study was to examine whether the first-generation HIV protease inhibitors having strong anti-cancer activity can be repurposed as inhibitors of ALKBH2. We selected four such inhibitors and performed in vitro binding analysis against ALKBH2 based on alterations of its intrinsic tryptophan fluorescence and differential scanning fluorimetry. The effect of these HIV protease inhibitors on the DNA repair activity of ALKBH2 was also evaluated. Interestingly, we observed that one of the inhibitors, ritonavir, could inhibit ALKBH2-mediated DNA repair significantly via competitive inhibition and sensitized cancer cells to alkylating agent methylmethane sulfonate (MMS). This work may provide new insights into the possibilities of utilizing HIV protease inhibitor ritonavir as a DNA repair antagonist.

Clinical Efficacy of the HIV Protease Inhibitor Indinavir in Combination with Chemotherapy for Advanced Classic Kaposi Sarcoma Treatment: A Single-Arm, Phase II Trial in the Elderly

Kaposi sarcoma is a rare angioproliferative disease associated with human herpes virus-8 (HHV-8) infection. Kaposi sarcoma is frequent and aggressive in HIV-infected people, whereas the classic form (CKS) generally has an indolent course. Notably, all conventional therapies against Kaposi sarcoma have only temporary efficacy. We have previously shown that indinavir, a HIV protease-inhibitor with direct antiangiogenic and antitumor activity, is safe and effective in patients with early CKS, whereas effects are less prominent in advanced disease, probably due to the larger tumor mass. Therefore, the clinical response to indinavir was assessed in patients with advanced CKS after debulking chemotherapy. This was a monocentric phase 2 trial in elderly with progressive/advanced CKS treated with debulking chemotherapy and indinavir combined, followed by a maintenance phase with indinavir alone. Secondary endpoints included safety and Kaposi sarcoma biomarker evaluation.All evaluable patients (22) responded to debulking therapy. Out of these, 16 entered the indinavir maintenance phase. The overall response rate at end of maintenance was 75% (estimated median response-duration 43 months). Moreover, most responders showed further clinical improvements (lesion number/nodularity) during maintenance and post-treatment follow-up. Notably, after relapse, progressors did not require systemic Kaposi sarcoma therapy and showed clinical improvements (including disease stabilization) remaining on study. Responders also showed immune status amelioration with a consistent B-cell increase and positive changes of other biomarkers, including anti-HHV-8 natural killer activity. In advanced CKS a strategy combining indinavir and chemotherapy is safe and associated with high and durable response rates and it could be rapidly adopted for the clinical management of these patients.

SIGNIFICANCE

This phase-2 trial showed that the HIV protease inhibitor indinavir may boost and extend the duration of the effects of chemotherapy in elderly with advanced progressive classic Kaposi sarcoma, without additional toxicity. Further, the amelioration of the immune status seen in responders suggests a better control of HHV-8 infection and tumor-cell killing. Thus, indinavir combined with chemotherapy may represent an important tool for the clinical management of classic Kaposi sarcoma in elderly patients.

Breast cancer therapy: from the perspective of glucose metabolism and glycosylation

Breast cancer is a leading cause of mortality and the most prevalent form of malignant tumor among women worldwide. Breast cancer cells exhibit an elevated glycolysis and altered glucose metabolism. Moreover, these cells display abnormal glycosylation patterns, influencing invasion, proliferation, metastasis, and drug resistance. Consequently, targeting glycolysis and mitigating abnormal glycosylation represent key therapeutic strategies for breast cancer. This review underscores the importance of protein glycosylation and glucose metabolism alterations in breast cancer. The current research efforts in developing effective interventions targeting glycolysis and glycosylation are further discussed.

Current trends and future prospects of drug repositioning in gastrointestinal oncology

Gastrointestinal (GI) cancers comprise a significant number of cancer cases worldwide and contribute to a high percentage of cancer-related deaths. To improve survival rates of GI cancer patients, it is important to find and implement more effective therapeutic strategies with better prognoses and fewer side effects. The development of new drugs can be a lengthy and expensive process, often involving clinical trials that may fail in the early stages. One strategy to address these challenges is drug repurposing (DR). Drug repurposing is a developmental strategy that involves using existing drugs approved for other diseases and leveraging their safety and pharmacological data to explore their potential use in treating different diseases. In this paper, we outline the existing therapeutic strategies and challenges associated with GI cancers and explore DR as a promising alternative approach. We have presented an extensive review of different DR methodologies, research efforts and examples of repurposed drugs within various GI cancer types, such as colorectal, pancreatic and liver cancers. Our aim is to provide a comprehensive overview of employing the DR approach in GI cancers to inform future research endeavors and clinical trials in this field.

PEGylated Liposomes Loaded with Carbamate Inhibitor ANP0903 Trigger Apoptosis by Enhancing ER Stress in HepG2 Cancer Cells

Liver cancer is one of the most common causes of cancer death worldwide. In recent years, substantial progress has been made in the development of systemic therapies, but there is still the need for new drugs and technologies that can increase the survival and quality of life of patients. The present investigation reports the development of a liposomal formulation of a carbamate molecule, reported as ANP0903, previously tested as an inhibitor of HIV-1 protease and now evaluated for its ability to induce cytotoxicity in hepatocellular carcinoma cell lines. PEGylated liposomes were prepared and characterized. Small, oligolamellar vesicles were produced, as demonstrated by light scattering results and TEM images. The physical stability of the vesicles in biological fluids was demonstrated in vitro, alongside the stability during storage. An enhanced cellular uptake was verified in HepG2 cells treated with liposomal ANP0903, resulting in a greater cytotoxicity. Several biological assays were performed to elucidate the molecular mechanisms explaining the proapoptotic effect of ANP0903. Our results allow us to hypothesize that the cytotoxic action in tumor cells is probably due to the inhibition of the proteasome, resulting in an increase in the amount of ubiquitinated proteins within the cells, which in turn triggers activation of autophagy and apoptosis processes, resulting in cell death. The proposed liposomal formulation represents a promising approach to deliver a novel antitumor agent to cancer cells and enhance its activity.

The E3 Ligases in Cervical Cancer and Endometrial Cancer

Endometrial (EC) and cervical (CC) cancers are the most prevalent malignancies of the female reproductive system. There is a global trend towards increasing incidence and mortality, with a decreasing age trend. E3 ligases label substrates with ubiquitin to regulate their activity and stability and are involved in various cellular functions. Studies have confirmed abnormal expression or mutations of E3 ligases in EC and CC, indicating their vital roles in the occurrence and progression of EC and CC. This paper provides an overview of the E3 ligases implicated in EC and CC and discusses their underlying mechanism. In addition, this review provides research advances in the target of ubiquitination processes in EC and CC.

Molecular Mechanisms of HIV Protease Inhibitors Against HPV-Associated Cervical Cancer: Restoration of TP53 Tumour Suppressor Activities

Cervical cancer is a Human Papilloma virus-related disease, which is on the rise in a number of countries, globally. Two essential oncogenes, E6 and E7, drive cell transformation and cancer development. These two oncoproteins target two of the most important tumour suppressors, p53 and pRB, for degradation through the ubiquitin ligase pathway, thus, blocking apoptosis activation and deregulation of cell cycle. This pathway can be exploited for anticancer therapeutic interventions, and Human Immunodeficiency Virus Protease Inhibitors (HIV-PIs) have attracted a lot of attention for this anticancer drug development. HIV-PIs have proven effective in treating HPV-positive cervical cancers and shown to restore impaired or deregulated p53 in HPV-associated cervical cancers by inhibiting the 26S proteasome. This review will evaluate the role players, such as HPV oncoproteins involved cervical cancer development and how they are targeted in HIV protease inhibitors-induced p53 restoration in cervical cancer. This review also covers the therapeutic potential of HIV protease inhibitors and molecular mechanisms behind the HIV protease inhibitors-induced p53-dependent anticancer activities against cervical cancer.

Overcoming Therapy Resistance in Colon Cancer by Drug Repurposing

Simple Summary

Despite improvements in standardized screening methods and the development of promising therapies for colorectal cancer (CRC), survival rates are still low. Drug repurposing offers an affordable solution to achieve new indications for previously approved drugs that could play a protagonist or adjuvant role in the treatment of CRC. In this review, we summarize the current data supporting drug repurposing as a feasible option for patients with CRC.

Abstract

Colorectal cancer (CRC) is the third most common cancer in the world. Despite improvement in standardized screening methods and the development of promising therapies, the 5-year survival rates are as low as 10% in the metastatic setting. The increasing life expectancy of the general population, higher rates of obesity, poor diet, and comorbidities contribute to the increasing trends in incidence. Drug repurposing offers an affordable solution to achieve new indications for previously approved drugs that could play a protagonist or adjuvant role in the treatment of CRC with the advantage of treating underlying comorbidities and decreasing chemotherapy toxicity. This review elaborates on the current data that supports drug repurposing as a feasible option for patients with CRC with a focus on the evidence and mechanism of action promising repurposed candidates that are widely used, including but not limited to anti-malarial, anti-helminthic, anti-inflammatory, anti-hypertensive, anti-hyperlipidemic, and anti-diabetic agents.

Kaposi’s Sarcoma Lesion Progression in BKV-Tat Transgenic Mice Is Increased by Inflammatory Cytokines and Blocked by Treatment with Anti-Tat Antibodies

Kaposi’s sarcoma (KS) is an angioproliferative tumor showing an increased frequency and aggressiveness in HIV-infected subjects (AIDS-KS), due to the combined effects of inflammatory cytokines (IC), angiogenic factors, and the HIV-1 Tat protein. While the introduction of effective combined antiretroviral regimens greatly improved AIDS-KS incidence and course, it continues to be an incurable disease and the development of new rational targeted therapies is warranted. We used the BKV/Tat transgenic mouse model to evaluate the effects of IC and anti-Tat antibodies (Abs) treatment on KS-like lesions arising in BKV/Tat mice. We demonstrated here that IC-treatment increases the severity and delays the regression of KS-like lesions. Further, anti-Tat Abs reduced KS-like lesion severity developing in IC-treated mice when anti-Tat Abs were administered at an early-stage of lesion development as compared to more advanced lesions. Early anti-Tat Abs treatment also accelerated KS-like lesion regression and reduced the rate of severe-grade lesions. This effect was more evident in the first weeks after Ab treatment, suggesting that a longer treatment with anti-Tat Abs might be even more effective, particularly if administered just after lesion development. Although preliminary, these results are encouraging, and the approach deserves further studies for the development of anti-Tat Ab-based therapies for AIDS-KS. Clinical studies specifically addressing the effect of anti-Tat antibodies in treating AIDS-KS are not yet available. Nevertheless, the effectiveness of anti-Tat antibodies in controlling HIV/AIDS progression, likely due to the neutralization of extracellular Tat activities, is suggested by several cross-sectional and longitudinal clinical studies, indicating that anti-Tat Ab treatment or Tat-based vaccines may be effective to treat AIDS-KS patients or prevent the tumor in individuals at risk.

Two Novel Precursors of the HIV-1 Protease Inhibitor Darunavir Target the UPR/Proteasome System in Human Hepatocellular Carcinoma Cell Line HepG2

Background: Several pre-clinical and clinical reports suggest that HIV-1 protease inhibitors, in addition to the antiretroviral properties, possess pleiotropic pharmacological effects including anticancer action. Therefore, we investigated the pro-apoptotic activity in tumor cells of two molecules, RDD-19 and RDD-142, which are hydroxyethylamine derivatives’ precursors of darunavir and several HIV-1 protease inhibitors. Methods: Three hepatoma cell lines and one non-pathological cell line were treated with RDD-19 and RDD-142, and cell viability was assessed. The expression levels of several markers for ER stress, autophagy, cellular ubiquitination, and Akt activation were quantified in HepG2 cells treated with RDD-19 and RDD-142 to evaluate apoptotic and non-apoptotic cell death. Results: RDD-19 and RDD-142 showed a greater dose-dependent cytotoxicity towards the hepatic tumor cell line HepG2 compared to the non-pathological hepatic cell line IHH. Both molecules caused two types of cell death, a caspase-dependent apoptosis, which was ascertained by a series of biochemical and morphological assays, and a caspase-independent death that was characterized by the induction of ER stress and autophagy. The strong increase of ubiquitinated proteins inside the cells suggested that the target of these molecules could be the proteasome and in silico molecular docking analysis that was used to support the plausibility of this hypothesis. Furthermore, cells treated with the two compounds displayed decreased levels of p-AKT, which interferes with cell survival and proliferation. Conclusions: These findings demonstrate that two compounds, RDD-19 and RDD-142, have pleiotropic effects and that they may represent promising anticancer candidates.

Prediction of Synergistic Drug Combinations for Prostate Cancer by Transcriptomic and Network Characteristics

Prostate cancer (PRAD) is a major cause of cancer-related deaths. Current monotherapies show limited efficacy due to often rapidly emerging resistance. Combination therapies could provide an alternative solution to address this problem with enhanced therapeutic effect, reduced cytotoxicity, and delayed the appearance of drug resistance. However, it is prohibitively cost and labor-intensive for the experimental approaches to pick out synergistic combinations from the millions of possibilities. Thus, it is highly desired to explore other efficient strategies to assist experimental researches. Inspired by the challenge, we construct the transcriptomics-based and network-based prediction models to quickly screen the potential drug combination for Prostate cancer, and further assess their performance by in vitro assays. The transcriptomics-based method screens nine possible combinations. However, the network-based method gives discrepancies for at least three drug pairs. Further experimental results indicate the dose-dependent effects of the three docetaxel-containing combinations, and confirm the synergistic effects of the other six combinations predicted by the transcriptomics-based model. For the network-based predictions, in vitro tests give opposite results to the two combinations (i.e. mitoxantrone-cyproheptadine and cabazitaxel-cyproheptadine). Namely, the transcriptomics-based method outperforms the network-based one for the specific disease like Prostate cancer, which provide guideline for selection of the computational methods in the drug combination screening. More importantly, six combinations (the three mitoxantrone-containing and the three cabazitaxel-containing combinations) are found to be promising candidates to synergistically conquer Prostate cancer.

HIV-1 Protease Inhibitors Slow HPV16-Driven Cell Proliferation through Targeted Depletion of Viral E6 and E7 Oncoproteins

High-risk human papillomavirus strain 16 (HPV16) causes oral and anogenital cancers through the activities of two viral oncoproteins, E6 and E7, that dysregulate the host p53 and pRb tumor suppressor pathways, respectively. The maintenance of HPV16-positive cancers requires constitutive expression of E6 and E7. Therefore, inactivating these proteins could provide the basis for an anticancer therapy. Herein we demonstrate that a subset of aspartyl protease inhibitor drugs currently used to treat HIV/AIDS cause marked reductions in HPV16 E6 and E7 protein levels using two independent cell culture models: HPV16-transformed CaSki cervical cancer cells and NIKS16 organotypic raft cultures (a 3-D HPV16-positive model of epithelial pre-cancer). Treatment of CaSki cells with some (lopinavir, ritonavir, nelfinavir, and saquinavir) but not other (indinavir and atazanavir) protease inhibitors reduced E6 and E7 protein levels, correlating with increased p53 protein levels and decreased cell viability. Long-term (>7 day) treatment of HPV16-positive NIKS16 raft cultures with saquinavir caused epithelial atrophy with no discernible effects on HPV-negative rafts, demonstrating selectivity. Saquinavir also reduced HPV16's effects on markers of the cellular autophagy pathway in NIKS16 rafts, a hallmark of HPV-driven pre-cancers. Taken together, these data suggest HIV-1 protease inhibitors be studied further in the context of treating or preventing HPV16-positive cancers.

HIV Protease Inhibitors Block HPV16-Induced Murine Cervical Carcinoma and Promote Vessel Normalization in Association with MMP-9 Inhibition and TIMP-3 Induction

Antiretrovirals belonging to the human immunodeficiency virus (HIV) protease inhibitor (HIV-PI) class exert inhibitory effects across several cancer types by targeting tumor cells and its microenvironment. Cervical carcinoma represents a leading cause of morbidity and mortality, particularly in women doubly infected with high-risk human papillomaviruses (HR-HPV) and HIV; of note, combined antiretroviral therapy has reduced cervical carcinoma onset and progression in HIV-infected women. We evaluated the effectiveness and mechanism(s) of action of HIV-PI against cervical carcinoma using a transgenic model of HR-HPV-induced estrogen-promoted cervical carcinoma (HPV16/E2) and found that treatment of mice with ritonavir-boosted HIV-PI, including indinavir, saquinavir, and lopinavir, blocked the growth and promoted the regression of murine cervical carcinoma. This was associated with inhibition of tumor angiogenesis, coupled to downregulation of matrix metalloproteinase (MMP)-9, reduction of VEGF/VEGFR2 complex, and concomitant upregulation of tissue inhibitor of metalloproteinase-3 (TIMP-3). HIV-PI also promoted deposition of collagen IV at the epithelial and vascular basement membrane and normalization of both vessel architecture and functionality. In agreement with this, HIV-PI reduced tumor hypoxia and enhanced the delivery and antitumor activity of conventional chemotherapy. Remarkably, TIMP-3 expression gradually decreased during progression of human dysplastic lesions into cervical carcinoma. This study identified the MMP-9/VEGF proangiogenic axis and its modulation by TIMP-3 as novel HIV-PI targets for the blockade of cervical intraepithelial neoplasia/cervical carcinoma development and invasiveness and the normalization of tumor vessel functions. These findings may lead to new therapeutic indications of HIV-PI to treat cervical carcinoma and other tumors in either HIV-infected or uninfected patients.

The Impact of Matrix Metalloproteinase-9 on the Sequential Steps of the Metastatic Process

In industrialized countries, cancer is the second leading cause of death after cardiovascular disease. Most cancer patients die because of metastases, which consist of the self-transplantation of malignant cells in anatomical sites other than the one from where the tumor arose. Disseminated cancer cells retain the phenotypic features of the primary tumor, and display very poor differentiation indices and functional regulation. Upon arrival at the target organ, they replace preexisting, normal cells, thereby permanently compromising the patient's health; the metastasis can, in turn, metastasize. The spread of cancer cells implies the degradation of the extracellular matrix by a variety of enzymes, among which the matrix metalloproteinase (MMP)-9 is particularly effective. This article reviews the available published literature concerning the important role that MMP-9 has in the metastatic process. Additionally, information is provided on therapeutic approaches aimed at counteracting, or even preventing, the development of metastasis via the use of MMP-9 antagonists.

The Anti-Angiogenic Effects of Anti-Human Immunodeficiency Virus Drugs

The growth and metastasis of malignant tumors benefit from the formation of blood vessels within the tumor area. There, new vessels originate from angiogenesis (the sprouting of pre-existing neighboring vessels) and/or vasculogenesis (the mobilization of bone marrow-derived endothelial cell precursors which incorporate in tumor vasculature and then differentiate into mature endothelial cells). These events are induced by soluble molecules (the angiogenic factors) and modulated by endothelial cell interactions with the perivascular matrix. Given angiogenesis/vasculogenesis relevance to tumor progression, anti-angiogenic drugs are often employed to buttress surgery, chemotherapy or radiation therapy in the treatment of a wide variety of cancers. Most of the anti-angiogenic drugs have been developed to functionally impair the angiogenic vascular endothelial growth factor: however, this leaves other angiogenic factors unaffected, hence leading to drug resistance and escape. Other anti-angiogenic strategies have exploited classical inhibitors of enzymes remodeling the perivascular matrix. Disappointingly, these inhibitors have been found toxic and/or ineffective in clinical trials, even though they block angiogenesis in pre-clinical models. These findings are stimulating the identification of other anti-angiogenic compounds. In this regard, it is noteworthy that drugs utilized for a long time to counteract human immune deficiency virus (HIV) can directly and effectively hamper molecular pathways leading to blood vessel formation. In this review the mechanisms leading to angiogenesis and vasculogenesis, and their susceptibility to anti-HIV drugs will be discussed.

The HIV protease inhibitor darunavir prevents kidney injury via HIV-independent mechanisms

HIV-associated nephropathy (HIVAN) is a rapidly progressive kidney disease that is caused by HIV infection of renal epithelial cells with subsequent expression of viral genes, including vpr. Antiretroviral therapy ameliorates HIVAN without eradicating HIV from the kidneys and the mechanism by which it protects kidneys is poorly understood. Since HIV protease inhibitors have "off target" cellular effects, we studied whether darunavir, the most commonly prescribed protease inhibitor, protects kidneys from HIV-induced injury via mechanisms independent of HIV protease and viral replication. Renal epithelial cells were transduced with lentiviruses encoding HIV (lacking protease and reverse transcriptase), Vpr, or vector control. Darunavir attenuated HIV and Vpr-induced activation of Stat3, Src, Erk, and cytokines, which are critical for HIVAN pathogenesis. We then studied HIV-transgenic mice, which develop HIVAN in the absence of HIV protease or reverse transcriptase. Mice were treated with darunavir, zidovudine, darunavir + zidovudine, or control. Darunavir and darunavir + zidovudine reduced albuminuria and histologic kidney injury and normalized expression of dysregulated proteins. RNA-seq analyses demonstrated that darunavir suppressed HIV-induced upregulation of immune response genes in human kidney cells. These data demonstrate that darunavir protects against HIV-induced renal injury via mechanisms that are independent of inhibition of HIV protease.

Extracellular binding of indinavir to matrix metalloproteinase-2 and the alpha-7-nicotinic acetylcholine receptor: implications for use in cancer treatment

Introduction

Results from recent studies have suggested a role for protease inhibitors in altering mechanisms involved in the initiation and proliferation of cancer cells. One such inhibitor, indinavir, may act as an anti-cancer agent by modulating the alpha-7-nicotinic acetylcholine receptor, which is a pro-carcinogenic protein that has been researched in conjunction with nicotine in lung cancer development. In our study, we compare indinavir's binding affinity towards α7-nAchR and MMP-2, another promoter of malignancy, to determine what extracellular effects the drug has before being internalized to inhibit HIV-1 protease.

Methods

A computer program, PyRx, was used to compare indinavir's binding affinity with digital models for α7-nAchR, MMP-2 and HIV-1 protease, which were then compared to the results of in vitro binding assays for these targets.

Results

PyRx testing predicted the highest binding affinity values for indinavir to MMP-2 (mean = 8.77 kcal/mol, S.D. = 0.29), followed by the α7-nAchR (mean = 8.53 kcal/mol, S.D. = 0.15) and HIV-1 protease (mean = 7.5 kcal/mol, S.D. = 0.44). In vitro, indinavir's mean percent inhibition of control values were 103.2 for HIV-1 protease, 5.3 for MMP-2, and 7.7 for the α7-nAchR.

Conclusions

Binding affinity values for indinavir to MMP-2 and α7-nAchR were not significantly different. Using PyRx to predict affinity compared with in vitro testing did not yield comparable results. However, indinavir was shown to slightly inhibit both α7-nAchR and MMP-2, which may have ramifications in the drug's delivery to the intracellularly located HIV-1 protease.

Senescence as a main mechanism of Ritonavir and Ritonavir-NO action against melanoma

The main focus of this study is exploring the effect and mechanism of two HIV-protease inhibitors: Ritonavir and Ritonavir-nitric oxide (Ritonavir-NO) on in vitro growth of melanoma cell lines. NO modification significantly improved the antitumor potential of Ritonavir, as the IC₅₀ values of Ritonavir-NO were approximately two times lower than IC₅₀ values of the parental compound. Our results showed for the first time, that both compounds induced senescence in primary and metastatic melanoma cell lines. This transformation was manifested as a change in cell morphology, enlargement of nuclei, increased cellular granulation, upregulation of β-galactosidase activity, lipofuscin granules appearance, higher production of reactive oxygen species and persistent inhibition of proliferation. The expression of p53, as one of the key regulators of senescence, was upregulated after 48 hours of Ritonavir-NO treatment only in metastatic B16F10 cells, ranking it as a late-response event. The development of senescent phenotype was consistent with the alteration of the cytoskeleton-as we observed diminished expression of vinculin, α-actin, and β-tubulin. Permanent inhibition of S6 protein by Ritonavir-NO, but not Ritonavir, could be responsible for a stronger antiproliferative potential of the NO-modified compound. Taken together, induction of senescent phenotype may provide an excellent platform for developing therapeutic approaches based on selective killing of senescent cells.

Breast cancer, human immunodeficiency virus and highly active antiretroviral treatment; implications for a high-rate seropositive region

Sub-Saharan Africa is the region in the world with the most people infected with the human immunodeficiency virus (HIV). The incidence of breast cancer is also rising in the region. This transcript focusses on the burden of these two diseases when they converge in the same populace. This comprehensive literature review of the topic suggests a trend towards an increasing incidence of breast cancer in the HIV-infected population, and the rationale for such a tendency is hypothesized, especially in the context of the availability of highly active antiretroviral therapy. Besides the age at diagnosis, all other clinical characteristics appear to be similar in HIV-positive and HIV-negative breast cancer populations. Outcomes of the different treatment modalities for breast cancer in HIV-positive patients are also appraised and finally innovative areas of future research are suggested along with plausible recommendations.

HPV-Associated Anal Cancer in the HIV/AIDS Patient

The prevalence of anal human papillomavirus (HPV) infection and anal high-grade squamous intraepithelial lesion (HSIL) remain high among HIV-infected individuals on effective antiretroviral therapy (ART). The incidence of HPV-related anal cancers has continued to increase since the introduction of ART. Therefore, ART may confer only limited benefit with respect to reducing the risk of anal HSIL and cancer. Efforts are in progress to define the efficacy of secondary prevention programs for prevention of anal cancer. In the modern ART era, anal cancer recurrence and survival outcomes are similar in HIV-infected and HIV-uninfected patients, but HIV-infected patients may experience more toxicities. This article reviews the current literature on HPV-associated anal cancer in the HIV-infected population, including epidemiology, screening, clinical characteristics, and treatment outcomes.

Diversity-Oriented Synthesis of Diol-Based Peptidomimetics as Potential HIV Protease Inhibitors and Antitumor Agents

Peptidomimetic HIV protease inhibitors are an important class of drugs used in the treatment of AIDS. The synthesis of a new type of diol-based peptidomimetics is described. Our route is flexible, uses d-glucal as an inexpensive starting material, and makes minimal use of protection/deprotection cycles. Binding affinities from molecular docking simulations suggest that these compounds are potential inhibitors of HIV protease. Moreover, the antiproliferative activities of compounds 33 a, 35 a, and 35 b on HT-29, M21, and MCF7 cancer cell lines are in the low micromolar range. The results provide a platform that could facilitate the development of medically relevant asymmetrical diol-based peptidomimetics.

The Impact of Human Papilloma Viruses, Matrix Metallo-Proteinases and HIV Protease Inhibitors on the Onset and Progression of Uterine Cervix Epithelial Tumors: A Review of Preclinical and Clinical Studies

Infection of uterine cervix epithelial cells by the Human Papilloma Viruses (HPV) is associated with the development of dysplastic/hyperplastic lesions, termed cervical intraepithelial neoplasia (CIN). CIN lesions may regress, persist or progress to invasive cervical carcinoma (CC), a leading cause of death worldwide. CIN is particularly frequent and aggressive in women infected by both HPV and the Human Immunodeficiency Virus (HIV), as compared to the general female population. In these individuals, however, therapeutic regimens employing HIV protease inhibitors (HIV-PI) have reduced CIN incidence and/or clinical progression, shedding light on the mechanism(s) of its development. This article reviews published work concerning: (i) the role of HPV proteins (including HPV-E5, E6 and E7) and of matrix-metalloproteinases (MMPs) in CIN evolution into invasive CC; and (ii) the effect of HIV-PI on events leading to CIN progression such as basement membrane and extracellular matrix invasion by HPV-positive CIN cells and the formation of new blood vessels. Results from the reviewed literature indicate that CIN clinical progression can be monitored by evaluating the expression of MMPs and HPV proteins and they suggest the use of HIV-PI or their derivatives for the block of CIN evolution into CC in both HIV-infected and uninfected women.

HIV antiretroviral exposure in pregnancy induces detrimental placenta vascular changes that are rescued by progesterone supplementation

Adverse birth outcomes are common in HIV-positive pregnant women receiving combination antiretroviral therapy (cART), especially when cART is initiated in early pregnancy. The mechanisms remain poorly understood. Using a mouse model we demonstrate that protease inhibitor based-cART exposure beginning on day 1 of pregnancy was associated with a pro-angiogenic/pro-branching shift in the placenta driven by lower Flt-1 levels and higher Gcm-1 expression. Micro-CT imaging revealed an increase in the number of arterioles in cART-treated placentas, which correlated with fetal growth restriction. Delaying initiation of cART, or supplementing cART-treated mice with progesterone, prevented the pro-angiogenic/pro-branching shift and the associated placenta vascular changes. In agreement with our mouse findings, we observed an increase in the number of terminal-villi capillaries in placentas from HIV-positive cART-exposed women compared to HIV-negative controls. Capillary number was inversely correlated to maternal progesterone levels. Our study provides evidence that cART exposure during pregnancy influences placenta vascular formation that may in turn contribute to fetal growth restriction. Our findings highlight the need for closer investigation of the placenta in HIV-positive pregnancies, particularly for pregnancies exposed to cART from conception, and suggest that progesterone supplementation could be investigated as a possible intervention to improve placenta function in HIV-positive pregnant women.

HIV-protease inhibitors for the treatment of cancer: Repositioning HIV protease inhibitors while developing more potent NO-hybridized derivatives?

The possible use of HIV protease inhibitors (HIV-PI) as new therapeutic option for the treatment of cancer primarily originated from their success in treating HIV-related Kaposi's sarcoma (KS). While these findings were initially attributed to immune reconstitution and better control of oncogenic viral infections, the number of reports on solid tumors, KS, lymphoma, fibrosarcoma, multiple myeloma and prostate cancer suggest other mechanisms for the anti-neoplastic activity of PIs. However, a major drawback for the possible adoption of HIV-PIs in the therapy of cancer relies on their relatively weak anticancer potency and important side effects. This has propelled several groups to generate derivatives of HIV-PIs for anticancer use, through modifications such as attachment of different moieties, ligands and transporters, including saquinavir-loaded folic acid conjugated nanoparticles and nitric oxide (NO) derivatives of HIV-PIs. In this article, we discuss the current preclinical and clinical evidences for the potential use of HIV-PIs, and of novel derivatives, such as saquinavir-NO in the treatment of cancer.

Combination antiretroviral therapy and cancer risk

PURPOSE OF REVIEW

To review the newest research about the effects of combination antiretroviral therapy (cART) on cancer risk.

RECENT FINDINGS

HIV+ persons are at increased risk of cancer. As this risk is higher for malignancies driven by viral and bacterial coinfections, classifying malignancies into infection-related and infection-unrelated has been an emerging trend. Cohorts have detected major reductions in the incidence of Kaposi sarcoma and non-Hodgkin lymphoma (NHL) following cART initiation among immunosuppressed HIV+ persons. However, recent randomized data indicate that cART reduces risk of Kaposi sarcoma and NHL also during early HIV infection before overt immunosuppression occurs. Long-term effects of cART exposure on cancer risk are not well defined; according to basic and epidemiological research, there might be specific associations of each cART class with distinct patterns of cancer risk.

SUMMARY

The relationship between cART exposure and cancer risk is complex and nuanced. It is an intriguing fact that, whether initiated during severe immunosuppression or not, cART reduces risk of Kaposi sarcoma and NHL. Further research should identify mediators of the benefit of immediate cART initiation in reducing cancer risk, understand the relationship between long-term cART exposure and cancer incidence and assess whether adjuvant anti-inflammatory therapies can reduce cancer risk during treated HIV infection.

Oxidative Stress Mediates the Antiproliferative Effects of Nelfinavir in Breast Cancer Cells

The discovery of the anti-proliferative activity of nelfinavir in HIV-free models has encouraged its investigation as anticancer drug. Although the molecular mechanism by which nelfinavir exerts antitumor activity is still unknown, its effects have been related to Akt inhibition. Here we tested the effects of nelfinavir on cell proliferation, viability and death in two human breast cancer cell lines and in human normal primary breast cells. To identify the mechanism of action of nelfinavir in breast cancer, we evaluated the involvement of the Akt pathway as well as the effects of nelfinavir on reactive oxygen species (ROS) production and ROS-related enzymes activities. Nelfinavir reduced breast cancer cell viability by inducing apoptosis and necrosis, without affecting primary normal breast cells. The antitumor activity of nelfinavir was related to alterations of the cell redox state, coupled with an increase of intracellular ROS production limited to cancer cells. Nelfinavir treated tumor cells also displayed a downregulation of the Akt pathway due to disruption of the Akt-HSP90 complex, and subsequent degradation of Akt. These effects resulted to be ROS dependent, suggesting that ROS production is the primary step of nelfinavir anticancer activity. The analysis of ROS-producers and ROS-detoxifying enzymes revealed that nelfinavir-mediated ROS production was strictly linked to flavoenzymes activation. We demonstrated that ROS enhancement represents the main molecular mechanism required to induce cell death by nelfinavir in breast cancer cells, thus supporting the development of new and more potent oxidizing molecules for breast cancer therapy.

Association between Time on Protease Inhibitors and the Incidence of Squamous Cell Carcinoma of the Anus among U.S. Male Veterans

Protease inhibitors (PIs) have been shown to have anti-tumor activity in addition to their antiretroviral properties. We sought to assess the association between PI use and the incidence of squamous cell carcinoma of the anus (SCCA) in HIV-infected individuals. We performed a retrospective cohort study among male US veterans diagnosed with HIV who were diagnosed between 1985 and 2010, using the Veterans Affairs HIV Clinical Case Registry (CCR). We calculated hazards ratios associated with PI use (both as percent time on PI and as 12-month intervals of PI use), utilizing time-dependent Cox models. We adjusted for risk factors, including age, race, year of enrolment into CCR, recent and nadir CD4, and percent time undetectable HIV viral load. A total of 28, 886 HIV-infected men met inclusion criteria. Of these, 373 were newly diagnosed with SCCA during the study period. In multivariate analysis, increasing percent time on PIs was associated with an increased risk of SCCA (aHR 1.07; 95% CI = 1.03–1.10 per 10% increase in time on PI). Poor immunologic recovery and virologic control, a history of condylomata acuminata, and CCR enrolment in the late combined antiretroviral therapy era were also associated with increased SCCA risk. Increasing percent time on a PI-based combined antiretroviral therapy regimen may be associated with an increased risk of developing SCCA in HIV-infected male US veterans. Future studies, better accounting for HIV control and treatment compliance, are necessary to further clarify this association.

The NO-modified HIV protease inhibitor as a valuable drug for hematological malignancies: Role of p70S6K

Covalent attachment of NO to the first approved HIV protease inhibitor Saquinavir (Saq-NO) expands the therapeutic potential of the original drug. Apart from retained antiviral activity, the modified drug exerts strong antitumor effects and lower toxicity. In the present study, we have evaluated the sensitivity of different hematological malignancies to Saq-NO. Saq-NO efficiently diminished the viability of Jurkat, Raji, HL-60 and K562 cells. While Jurkat and Raji cells (established from pediatric patients) displayed abrogated proliferative potential, HL-60 and K652 cells (originated from adults) exposed to Saq-NO treatment underwent caspase dependent apoptosis. In addition, similar sensitivity to Saq-NO was observed in mononuclear blood cells obtained from pediatric patients with acute lymphoblastic leukemia (ALL) and adult patients with acute myeloid leukemia (AML). Western blot analysis indicated p70S6 kinase as a possible intracellular target of Saq-NO action. Moreover, the addition of a NO moiety to Lopinavir resulted in improved antitumor potential as compared to the parental compound, suggesting that NO-derived HIV protease inhibitors are a potential new source of anticancer drugs with unique mode of action.

Factors contributing to risk for cancer among HIV-infected individuals, and evidence that earlier combination antiretroviral therapy will alter this risk

PURPOSE OF REVIEW

To critically appraise recent published literature about factors associated with cancer risk likely to be influenced by combination antiretroviral therapy (cART) in HIV-infected individuals, and the potential of earlier cART initiation to reduce this risk.

RECENT FINDINGS

Factors leading to increased risk of non-AIDS-defining malignancies (NADMs) in particular remain poorly understood. Immunodeficiency appears to be key, whereas evidence is emerging that a direct pro-oncogenic effect of HIV, activated inflammatory and coagulation pathways, and cART toxicity may also contribute. By reducing HIV replication, improving immune function, and limiting chronic inflammation, cART initiation at higher CD4 cell counts may, therefore, reduce NADM risk. However, cART only partly normalizes enhanced inflammation and coagulation seen during HIV infection and conflicting laboratory and epidemiological data have been reported as to whether (and how) cART affects NADM risk. Furthermore, secondary analyses of randomized controlled trials comparing early versus delayed cART initiation were inconclusive.

SUMMARY

Continuous epidemiological surveillance is warranted to monitor trends in cancer incidence among HIV-infected individuals and to better understand the impact of earlier cART on NADM risk. The role of adjuvant anti-inflammatory or antithrombotic therapies to reduce cancer risk deserves further investigation.

The HIV protease inhibitor indinavir down-regulates the expression of the pro-angiogenic MT1-MMP by human endothelial cells

In addition to contrast human immunodeficiency virus (HIV) replication, the HIV protease inhibitors (HIV-PI) have reduced tumour incidence or clinical progression in infected patients. In this regard, we have previously shown that, independently of its anti-viral activity, the HIV-PI indinavir (IDV) directly blocks matrix metalloproteinase (MMP)-2 proteolytic activation, thus efficiently inhibiting tumour angiogenesis in vitro, in animal models, and in humans. Herein we investigated the molecular mechanism for IDV anti-angiogenic effect. We found that treatment of human primary endothelial cells with therapeutic IDV concentrations decreases the expression of membrane type (MT)1-MMP, which is the major activator of MMP-2. This occurs for both the constitutive expression of MT1-MMP and that up-regulated by angiogenic factors. In either cases, reduction of MT1-MMP levels by IDV is preceded by the inhibition of the binding of the specificity protein (Sp)1 transcription factor to the promoter region of the MT1-MMP gene in endothelial cell nuclei. As MT1-MMP is key for tumour angiogenesis, these results support the use of IDV or its derivatives in anti-cancer therapy. This is recommended by the low toxicity of the drug, and the large body of data on its pharmacokinetic.

HIV protease inhibitor Lopinavir induces apoptosis of primary effusion lymphoma cells via suppression of NF-κB pathway

Primary effusion lymphoma (PEL) is a non-Hodgkin lymphoma that occurs predominantly in patients with advanced AIDS. In this study, we examined the effect of HIV protease inhibitors, Lopinavir (LPV), Ritonavir (RTV) and Darunavir (DRV) on PEL cell lines in vitro and in vivo. LPV and RTV, but not DRV induced caspase-dependent apoptosis and suppressed NF-κB activity by inhibiting IKK phosphorylation in PEL cells. In a PEL xenograft mouse model, LPV significantly inhibited the growth and invasion of PEL cells. These results suggest that LPV may have promise for the treatment and prevention of PEL, which occurs in HIV/AIDS patients.

The antiretroviral agent saquinavir enhances hTERT expression and telomerase activity in human T leukaemia cells in vitro

BACKGROUND

Saquinavir, a protease inhibitor utilized in HIV infection, shows antitumor activity in various experimental models. In previous studies performed in our laboratory the drug was found to induce a substantial increase of telomerase activity in normal peripheral blood mononuclear cells. Aim of the present investigation was to test whether saquinavir was able to increase telomerase activity and the expression of the catalytic subunit of telomerase, hTERT, in human malignant hematopoietic cells.

METHODS

Human Jurkat CD4+ T cell leukaemia cell line was used throughout the present study. The antiproliferative effect of saquinavir was tested by the MTT assay. Telomerase activity was determined according to the telomeric repeat amplification protocol. The expression of hTERT mRNA was semi-quantitative evaluated by RT-PCR amplification and quantitative Real Time PCR. The binding of the transcription factor c-Myc to its specific E-Box DNA binding-site of hTERT promoter was analyzed by Electophoretic Mobility Shift Assay (EMSA). The amount of c-Myc in cytoplasm and nucleus of leukemia cells was determined by Western Blot analysis, and c-Myc down-regulation was obtained by siRNA transfection.

RESULTS

Saquinavir produced a substantial increase of telomerase activity in Jurkat cells in vitro without increasing but rather reducing target cell proliferation rate. Telomerase up-regulation appeared to be the result of enhanced expression of hTERT. Saquinavir-mediated up-regulation of hTERT gene was the result of the increased binding of proteins to the E-Box sequence of the promoter. Moreover, saquinavir amplified the expression of c-Myc especially in the nuclear cell fraction. The direct influence of saquinavir on this transcription factor was also demonstrated by the antagonistic effect of the drug on siRNA induced c-Myc suppression. Since c-Myc is the main responsible for hTERT transcription, these findings suggest that the main mechanism underlying saquinavir-induced telomerase activation is mediated by c-Myc up-regulation.

CONCLUSIONS

Saquinavir augments hTERT expression while inhibiting leukemic cell growth. Experimental evidences show that this effect is mediated by saquinavir-influenced increase of c-Myc levels. This could have relevance in terms of enhanced hTERT-dependent tumor cell immunogenicity and suggests new paharmacological approaches interfering with c-Myc dependent pathways.

Saquinavir-NO inhibits S6 kinase activity, impairs secretion of the encephalytogenic cytokines interleukin-17 and interferon-gamma and ameliorates experimental autoimmune encephalomyelitis

NO-hybridization of the HIV protease inhibitor Saquinavir generates a new chemical entity named Saq-NO, that retains the anti-viral activity and exerts lower toxicity. We show that Saq-NO inhibited the generation of various cytokines in ConA-stimulated unfractionated murine spleen cells and rat lymph nodes stimulated with ConA as well as in purified CD4(+) T cells in vitro and reduced the circulating levels of cytokines in mice challenged with anti-CD3 antibody. Furthermore, Saq-NO reduced IL-17 and IFN-γ production in myelin basic protein (MBP)-specific cells isolated from rats immunized with MBP. These findings translated well into the in vivo setting as Saq-NO ameliorated the course of the disease in two preclinical models of multiple sclerosis. Our results demonstrate that Saq-NO exerts immunomodulatory effects that warrant studies on its application in autoimmune diseases.

Metabolic effects of the HIV protease inhibitor--saquinavir in differentiating human preadipocytes

BACKGROUND

The iatrogenic, HIV-related lipodystrophy is associated with development of the significant metabolic and cardiovascular complications. The underlying mechanisms of antiretroviral (ARV) drugs are not completely explored.

METHODS

The aim of the study was to characterize effects of the protease inhibitor (PI)--saquinavir (SQV) on metabolic functions, and gene expression during differentiation in cells (Chub-S7) culture.

RESULTS

SQV in concentrations observed during antiretroviral therapy (ART) significantly decreased mitochondrial membrane potential (MMP), oxygen consumption and ATP generation. The effects were greater in already differentiated cells. This was accompanied by characteristic changes in the expression of the genes involved in endoplasmic reticulum (ER) stress, and differentiation (lipid droplet formation) process such as: WNT10a, C/EBPa, AFT4, CIDEC, ADIPOQ, LPIN1.

CONCLUSIONS

The results indicate that SQV affects not only metabolic (mitochondrial) activity of adipocytes, but affects the expression of genes related to differentiation and to a lesser extent to cell apoptosis.

Therapeutic potential of nitric oxide-modified drugs in colon cancer cells

We have examined the influence of the nitric oxide (NO)-modified anti-inflammatory drug (S,R)-3-phenyl-4,5-dihydro-5-isoxasole acetic acid (VGX-1027) named GIT-27NO or the NO-modified antiviral drug saquinavir (Saq) named Saq-NO on two colon cancer cell lines, mouse CT26CL25 and human HCT116. The effects of the drugs on cell viability, apoptosis, proliferation, and metastatic potential were analyzed. The release of NO and oxygen and nitrogen species was also determined. The efficacy of the drugs was evaluated in vivo in BALB/c mice injected with CT26CL25 cells. Both agents suppressed the growth of colon cancer cells in vitro and reduced tumor volume in syngeneic BALB/c mice. However, their mechanisms of action were different because GIT-27NO released larger amounts of nitrite than Saq-NO in cell cultures and its antitumor action depended on the intracellular NO release inside the cells. On the contrary, Saq-NO released barely detectable amounts of NO and its antitumor action was NO-independent. In fact, cotreatment with an NO-peroxynitrite scavenger revealed that GIT-27NO but not Saq-NO acts through peroxynitrite-mediated cell destruction. At the cellular level, GIT-27NO prevalently induced proapoptotic signals followed by caspase-dependent apoptosis. In contrast, Saq-NO blocked cell proliferation, changed the adhesive, migratory, and invasive properties of the cells, and decreased metastatic potential in vivo. In conclusion, differences in NO release and oxidative stress generation between GIT-27NO and Saq-NO resulted in different mechanisms that caused cell death.

The HIV-1 protease inhibitor nelfinavir activates PP2 and inhibits MAPK signaling in macrophages: a pathway to reduce inflammation

The HIV-1 PI NFV has off-target effects upon host enzymes, including inhibition of the 20S proteasome, resulting in activation of PP1. HIV-1-associated monocyte/macrophage activation, in part a result of systemically elevated levels of microbial products including LPS, is associated with risk of mortality, independent of viremia or CD4 T cell loss. This study tested the hypothesis that activation of protein phosphatases by NFV would reduce activation of monocytes/macrophages through dephosphorylation of signal transduction proteins. NFV uniquely blocked LPS-induced production by human monocyte-derived macrophages of the inflammatory cytokines TNF and IL-6, as well as sCD14. Although NFV failed to modulate NF-κB, NFV treatment reduced phosphorylation of AKT and MAPKs. Inhibition of PP2 with okadaic acid blocked the anti-inflammatory effect of NFV, whereas the PP1 inhibitor calyculin A failed to counter the anti-inflammatory effects of NFV. For in vivo studies, plasma sCD14 and LPS were monitored in a cohort of 31 pediatric HIV-1 patients for over 2 years of therapy. Therapy, including NFV, reduced sCD14 levels significantly compared with IDV or RTV, independent of ΔLPS levels, VL, CD4 T cell frequency, or age. The hypothesis was supported as NFV induced activation of PP2 in macrophages, resulting in disruption of inflammatory cell signaling pathways. In vivo evidence supports that NFV may offer beneficial effects independent of antiviral activity by reducing severity of chronic innate immune activation in HIV-1 infection.

Ritonavir or saquinavir impairs the invasion of cervical intraepithelial neoplasia cells via a reduction of MMP expression and activity

OBJECTIVE AND DESIGN

Treatment of human immunodeficiency virus (HIV)-infected women with the highly active antiretroviral therapy (HAART) has reduced the onset of uterine cervical intraepithelial neoplasia (CIN), and halted its progression to cervical carcinoma. We and others demonstrated that the HIV protease inhibitors (HIV-PIs) used in HAART can exert direct antitumour activities also in HIV-free preclinical or clinical models. As uterine cervical carcinoma is a leading cause of death in women independently of HIV infection, herein we assessed the impact of therapeutic concentrations of HIV-PIs including indinavir (IDV), saquinavir (SQV) or ritonavir (RTV) on cells obtained from CIN or cervical carcinoma lesions of HIV-negative women.

METHODS

HIV-PI effects were evaluated by cell invasion, growth or toxicity assays, and by RNA, protein or zymogram analyses.

RESULTS

Both SQV and RTV inhibited CIN cell invasion, and this was paralleled by a reduced expression and proteolytic activity of the matrix metalloproteinase (MMP)-2 and 9 in treated cells. SQV and RTV also reduced CIN cell growth rate, but did not affect the invasion or growth of cells derived from highly progressed cervical carcinoma.

CONCLUSION

As MMP-2 and MMP-9 have a key role in CIN evolution into cervical carcinoma, these results support the use of SQV or RTV for the block of CIN clinical progression in either HIV-infected or uninfected patients.

Armitage lecture 2010: Understanding treatment effects: the value of integrating longitudinal data and survival analysis

There is a single-minded focus on events in survival analysis, and we often ignore longitudinal data that are collected together with the event data. This is due to a lack of methodology but also a result of the artificial distinction between survival and longitudinal data analyses. Understanding the dynamics of such processes is important but has been hampered by a lack of appreciation of the difference between confirmatory and exploratory causal inferences. The latter represents an attempt at elucidating mechanisms by applying mediation analysis to statistical data and will usually be of a more tentative character than a confirmatory analysis. The concept of local independence and the associated graphs are useful. This is related to Granger causality, an important method from econometrics that is generally undervalued by statisticians. This causality concept is different from the counterfactual one since it lacks lacks the intervention aspect. The notion that one can intervene at will in naturally occurring processes, which seems to underly much of modern causal inference, is problematic when studying mediation and mechanisms. It is natural to assume a stochastic process point of view when analyzing dynamic relationships. We present some examples to illustrate this. It is not clear how survival analysis must be developed to handle the complex life-history data that are increasingly being collected today. We give some suggestions.

Nelfinavir induces radiation sensitization in pituitary adenoma cells

Pituitary adenomas with local invasion and high secretory activity remain a therapeutic challenge. The HIV protease inhibitor nelfinavir is a radiosensitizer in multiple tumor models. We tested nelfinavir as a radiosensitizer in pituitary adenoma cells in vitro and in vivo. We examined the effect of nelfinavir with radiation on in vitro cell viability, clonogenic survival, apoptosis, prolactin secretion, cell cycle distribution, and the PI3K-AKT-mTOR pathway. We evaluated tumor growth delay and confirmed nelfinavir's effect on the PI3K-AKT-mTOR pathway in a hind-flank model. Nelfinavir sensitized pituitary adenoma cells to ionizing radiation as shown by viability assays and clonogenic assay with an enhancement ratio of 1.2 (p < 0.05). There is increased apoptotic cell death, as determined by annexin-V expression and cleaved caspase-3 levels. Nelfinavir does not affect prolactin secretion or cell cycle distribution. In vivo, untreated tumors reached 4-fold volume in 12 days, 17 days with nelfinavir treatment, 27 days with radiation 6 Gy, and 41 days with nelfinavir plus radiation (one-way ANOVA p < 0.001). Decreased phospho-S6 on Western blotting in vitro and immunohistochemistry in vivo demonstrated nelfinavir inhibition of the PI3K-AKT-mTOR pathway. Our data suggests a promising combination therapy with nelfinavir plus radiation in pituitary adenomas, which should be investigated in clinical studies.