Placental metastasis from maternal NUT carcinoma: diagnostic pitfalls and challenges.

We report a young pregnant woman with large midline thoracic mass and markedly elevated serum alpha-fetoprotein (AFP) levels. Initially suspected as a germ cell tumour (GCT) due to age, site, and high AFP levels, a biopsy unveiled a high-grade malignant tumour characterised by undifferentiated monotonous cells. Although tumour cells exhibited positive AFP, the overall immunoprofile did not provide additional evidence to support GCT. Further work-up showed positive for NUT (nuclear protein in testis) immunostaining and the presence of BRD4-NUT1 fusion, confirming the diagnosis of NUT carcinoma. On radiology, there were extensive metastases to lungs, liver, vertebrae, and placenta. Despite aggressive chemotherapy, radiotherapy and immunotherapy, she did not respond to the therapies. Fortunately, her child was not affected by the carcinoma. This is the first case highlighting that thoracic lung primary NUT carcinoma can spread to the placenta and manifest with elevated serum AFP levels, potentially leading to misdiagnosis as GCT both clinically and pathologically.

Intrathecal trastuzumab versus alternate routes of delivery for HER2-targeted therapies in patients with HER2+ breast cancer leptomeningeal metastases.

BACKGROUND: Patients with HER2+ breast cancer (BC) frequently develop leptomeningeal metastases (LM). While HER2-targeted therapies have demonstrated efficacy in the neoadjuvant, adjuvant, and metastatic settings, including for parenchymal brain metastases, their efficacy for patients with LM has not been studied in a randomized controlled trial. However, several single-armed prospective studies, case series and case reports have studied oral, intravenous, or intrathecally administered HER2-targeted therapy regimens for patients with HER2+ BC LM. METHODS: We conducted a systematic review and meta-analysis of individual patient data to evaluate the efficacy of HER2-targeted therapies in HER2+ BC LM in accordance with PRISMA guidelines. Targeted therapies evaluated were trastuzumab (intrathecal or intravenous), pertuzumab, lapatinib, neratinib, tucatinib, trastuzumab-emtansine and trastuzumab-deruxtecan. The primary endpoint was overall survival (OS), with CNS-specific progression-free survival (PFS) as a secondary endpoint. RESULTS: 7780 abstracts were screened, identifying 45 publications with 208 patients, corresponding to 275 lines of HER2-targeted therapy for BC LM which met inclusion criteria. In univariable and multivariable analyses, we observed no significant difference in OS and CNS-specific PFS between intrathecal trastuzumab compared to oral or intravenous administration of HER2-targeted therapy. Anti-HER2 monoclonal antibody-based regimens did not demonstrate superiority over HER2 tyrosine kinase inhibitors. In a cohort of 15 patients, treatment with trastuzumab-deruxtecan was associated with prolonged OS compared to other HER2-targeted therapies and compared to trastuzumab-emtansine. CONCLUSIONS: The results of this meta-analysis, comprising the limited data available, suggest that intrathecal administration of HER2-targeted therapy for patients with HER2+ BC LM confers no additional benefit over oral and/or IV treatment regimens. Although the number of patients receiving trastuzumab deruxtecan in this cohort is small, this novel agent offers promise for this patient population and requires further investigation in prospective studies.

PARP Inhibition Sensitizes Breast Cancer Cells to Eribulin.

BACKGROUND: Poly(ADP-ribose) polymerases 1 and 2 (PARP1, 2), and 3 mediate protein modifications that facilitate the recruitment of DNA repair factors to single and double strand breaks. PARP3 is unique in that it is also required for efficient mitotic progression and stabilization of the mitotic spindle. Eribulin, an anti-microtubule agent used clinically to treat breast cancer, exerts its cytotoxicity by altering microtubule dynamics resulting in cell cycle arrest and apoptosis. Herein, we hypothesize that the pan PARP inhibitor olaparib has the potential to enhance the cytotoxicity of eribulin by halting mitosis through inhibition of PARP3. METHODS: The effect of olaparib on eribulin cytotoxicity was assessed using the Sulforhodamine (SRB) assay, with two triple negative breast cancer cell lines and an estrogen receptor positive (ER+)/human epidermal growth factor receptor 2 negative (HER2-) breast cancer cell line. Alteration by the treatments on PARP3 activity and microtubule dynamics were assessed utilizing a chemiluminescent enzymatic assay and immunofluorescence, respectively. The effect of the treatments on cell cycle progression and apoptosis induction were assessed by flow cytometry using propidium iodide and Annexin V staining, respectively. RESULTS: Our results demonstrate that non-cytotoxic concentrations of olaparib sensitize breast cancer cells regardless of ER status. Mechanistically, our results indicate that olaparib potentiates eribulin-induced cell cycle arrest at the G2/M boundary, PARP3 inhibition and microtubule destabilizing resulting in mitotic catastrophe and apoptosis. CONCLUSIONS: In breast cancer (regardless of ER status) settings, treatment outcomes could be improved by the incorporation of olaparib in eribulin treatment regimens.

The risks associated with the widespread use of telemedicine in oncology: Four cases and review of the literature.

BACKGROUND: COVID-19 changed the way we practice oncology in multiple ways. Because most cancer patients are comorbid or immunocompromised, we are trying as much as possible to reduce their risk of infection. Marginal just 2 years ago, telemedicine quickly became preeminent with the pandemic to reduce hospital exposure. However, using only virtual visits in oncology patients risk delaying cancer diagnosis or the identification of a complication. CASE SERIES: We present here four cases where a serious medical problem evident on physical exam was overlooked during a virtual visit. Two of our patients experienced a delay in cancer diagnosis thus putting them at risk of local or distant spread. The two others were established oncology patients where a serious medical complication was missed on a virtual visit. CONCLUSIONS: Now more than a year into the pandemic, telemedicine has clearly been a useful tool by limiting unnecessary hospital visits. Yet, as our cases illustrate, its use in oncology without clear boundary can undermine the quality of care. Now that effective vaccines are reducing the transmission and the severity of infection, most oncology patients can be evaluated by a real-time visit.

IND.216: a phase II study of buparlisib and associated biomarkers, raptor and p70S6K, in patients with relapsed and refractory chronic lymphocytic leukemia.

Buparlisib is an orally available pan-Class I PI3K inhibitor, that is more potent than idelalisib in vitro. Its distinct toxicities include hyperglycemia, hypertension, and mood disturbance. IND216 is a single arm phase II trial of buparlisib in Relapsed/refractory (R/R) chronic lymphocytic leukemia (CLL). Fourteen patients were enrolled, 13 were evaluable for response and toxicity. Six of 13 patients had a partial response (46%) with a median duration of response of 15.5 months, all 11 patients with tumor assessment experienced tumor shrinkage. The most common adverse events (≥15%) were hyperglycemia, fatigue, anxiety, and gastrointestinal toxicities; all were < grade 3 except for fatigue. Three patients stopped therapy for alterations in mood. Lower levels of raptor were significantly associated with greater tumor shrinkage, suggesting that raptor could be a biomarker for response. This requires further validation in a larger CLL patient cohort. The clinical activity of buparlisib is comparable to other phosphatidylinositol-3-kinase inhibitors, with a different toxicity profile.Novelty and impactBuparlisib, an oral, pan PI3 kinase inhibitor, is associated with a 46% partial response rate among patients with relapse chronic lymphocytic leukemia (CLL). This is a similar clinical activity to other phosphatidylinositol-3-kinase inhibitors tested. However, buparlisib has a distinct toxicity profile, characterized by hyperglycemia, hypertension, and mood alteration. In agreement with our previous preclinical study, our results suggest that basal raptor expression in CLL correlates with clinical response to buparlisib.

PARP3 inhibitors ME0328 and olaparib potentiate vinorelbine sensitization in breast cancer cell lines.

PURPOSE: PARP-3 is member of the PARP family of poly (ADP-ribose) polymerases involved in ADPribosylation. PARPs are involved in the basic mechanisms of DNA repair. PARP3, a critical player for efficient mitotic progression, is required for the stabilization of the mitotic spindle by regulation of the mitotic components, NuMA and Tankyrase 1. METHODS: The sensitization effect of vinorelbine on PARP3 inhibition-induced cytotoxicity was assessed by the SRB assay. The contribution of programed cell death and cell cycle arrest to the sensitization effect were determined by assessing changes in Annexin V, a marker of apoptosis. Alterations in cell cycle progression were assessed by cell cycle analysis. We used immunofluorescence to assess the effect of vinorelbine and/or PARP3 inhibitors on tubulin and microtubule depolarization. The PARP3 chemiluminescent assay kit was used for PARP3 activity. RESULTS: PARP3 inhibitors sensitize breast cancer cells to vinorelbine, a vinca alkaloid used in the treatment of metastatic breast cancer. Olaparib which was originally described as a PARP1 and 2 inhibitor has recently been shown to be a potent PARP3 inhibitor while ME0328 is a more selective PARP3 inhibitor. The combination of vinorelbine with nontoxic concentrations of ME0328 or olaparib reduces vinorelbine resistance by 10 and 17 fold, respectively, potentiating vinorelbine-induced arrest at the G2/M boundary. In addition, PARP3 inhibition potentiates vinorelbine interaction with tubulin. Furthermore, olaparib or ME0328 potentiates vinorelbine-induced PARP3 inhibition, mitotic arrest, and apoptosis. CONCLUSION: Our results indicated this approach with PARP3 inhibitors and vinorelbine is unique and promising for breast cancer patients with metastases. This combination could significantly increase the survival of breast cancer patients with metastases.

Precision spherical nucleic acids for delivery of anticancer drugs.

We report a spherical nucleic acid (SNA) system for the delivery of BKM120, an anticancer drug for treatment of chronic lymphocytic leukemia (CLL). While promising for cancer treatment, this drug crosses the blood-brain barrier causing significant side-effects in patients. The DNA nanoparticle encapsulates BKM120 in high efficiency, and is unparalleled in its monodispersity, ease of synthesis and stability in different biological media and in serum. These DNA nanostructures demonstrate efficient uptake in human cervical cancer (HeLa) cells, and increased internalization of cargo. In vitro studies show that BKM120-loaded nanoparticles promote apoptosis in primary patient CLL lymphocytes, and act as sensitizers of other antitumor drugs, without causing non-specific inflammation. Evaluation of this drug delivery system in vivo shows long circulation times up to 24 hours, full body distribution, accumulation at tumor sites and minimal leakage through the blood-brain barrier. Our results demonstrate the great potential of these delivery vehicles as a general platform for chemotherapeutic drug delivery.

Fulvestrant 500 mg versus anastrozole 1 mg for hormone receptor-positive advanced breast cancer (FALCON): an international, randomised, double-blind, phase 3 trial.

BACKGROUND: Aromatase inhibitors are a standard of care for hormone receptor-positive locally advanced or metastatic breast cancer. We investigated whether the selective oestrogen receptor degrader fulvestrant could improve progression-free survival compared with anastrozole in postmenopausal patients who had not received previous endocrine therapy. METHODS: In this phase 3, randomised, double-blind trial, we recruited eligible patients with histologically confirmed oestrogen receptor-positive or progesterone receptor-positive, or both, locally advanced or metastatic breast cancer from 113 academic hospitals and community centres in 20 countries. Eligible patients were endocrine therapy-naive, with WHO performance status 0-2, and at least one measurable or non-measurable lesion. Patients were randomly assigned (1:1) to fulvestrant (500 mg intramuscular injection; on days 0, 14, 28, then every 28 days thereafter) or anastrozole (1 mg orally daily) using a computer-generated randomisation scheme. The primary endpoint was progression-free survival, determined by Response Evaluation Criteria in Solid Tumors version 1·1, intervention by surgery or radiotherapy because of disease deterioration, or death from any cause, assessed in the intention-to-treat population. Safety outcomes were assessed in all patients who received at least one dose of randomised treatment (including placebo). This trial is registered with ClinicalTrials.gov, number NCT01602380. FINDINGS: Between Oct 17, 2012, and July 11, 2014, 524 patients were enrolled to this study. Of these, 462 patients were randomised (230 to receive fulvestrant and 232 to receive anastrozole). Progression-free survival was significantly longer in the fulvestrant group than in the anastrozole group (hazard ratio [HR] 0·797, 95% CI 0·637-0·999, p=0·0486). Median progression-free survival was 16·6 months (95% CI 13·83-20·99) in the fulvestrant group versus 13·8 months (11·99-16·59) in the anastrozole group. The most common adverse events were arthralgia (38 [17%] in the fulvestrant group vs 24 [10%] in the anastrozole group) and hot flushes (26 [11%] in the fulvestrant group vs 24 [10%] in the anastrozole group). 16 (7%) of 228 patients in in the fulvestrant group and 11 (5%) of 232 patients in the anastrozole group discontinued because of adverse events. INTERPRETATION: Fulvestrant has superior efficacy and is a preferred treatment option for patients with hormone receptor-positive locally advanced or metastatic breast cancer who have not received previous endocrine therapy compared with a third-generation aromatase inhibitor, a standard of care for first-line treatment of these patients. FUNDING: AstraZeneca.

Phase I/II Trial of Sorafenib in Combination with Vinorelbine as First-Line Chemotherapy for Metastatic Breast Cancer.

BACKGROUND: Preclinical models have reported a synergistic interaction between sorafenib and vinorelbine. We investigated the toxicity, efficacy, and pharmacokinetics interaction of this combination as first-line treatment for patients with metastatic breast cancer. METHODS: Patients were HER2-negative and treated with vinorelbine 30 mg/m2 IV days 1,8 every 21 plus daily oral sorafenib. In the phase I portion (3+3 design) patients received sorafenib 200 mg BID (cohort 1) or 400 mg BID (cohort 2). In the phase II expansion, 21 more evaluable patients were planned to receive the maximum tolerated dose (MTD). Pharmacokinetic analysis was performed in 6 patients: blood concentrations were compared for each drug in the presence or absence of the other drug. RESULTS: In cohort 1, one patient experienced a dose-limiting toxicity (DLT) (grade 3 pancreatitis), requiring the expansion of this cohort to 6 patients, without further documented DLTs. In cohort 2, one patient of six experienced a grade 4 DLT (asymptomatic rise in amylase not requiring drug discontinuation), establishing this dose level as the MTD (sorafenib 400 mg BID). After expansion at the MTD, a total of 27 patients (median age 57) were treated for a median of 8 cycles. One grade 5 febrile neutropenia occurred. With repeated cycles, 52% of patients required at least 1 dose reduction of either drug. One patient experienced a sustained grade 3 fatigue resulting in treatment discontinuation. The response rate was 30%. Median PFS was 5.7 months (95% CI 4.4-7.6), and clinical benefit (absence of disease progression at 6 months) was 48%. PK analysis showed a significant interaction between the two drugs, resulting in a higher Cmax of vinorelbine in the presence of sorafenib. CONCLUSION: The combination of sorafenib and vinorelbine at full doses is feasible but not devoid of toxicity, likely also due to a significant PK interaction. TRIAL REGISTRATION: ClinicalTrials.gov NCT00764972.

Complete response and long-term survival of leptomeningeal carcinomatosis from breast cancer with maintenance endocrine therapy.

Leptomeningeal carcinomatosis carries a poor prognosis in breast cancer. Treatment modalities are geared towards tumour molecular characteristics, as well as symptoms and patient performance status. It has previously been postulated that endocrine treatments used for the treatment of metastatic breast cancer do cross the blood-brain barrier and can achieve antineoplastic effects in the central nervous system. We report a case of metastatic breast cancer in a 65-year-old woman who developed leptomeningeal carcinomatosis. She was initially treated with intrathecal methotrexate, which was stopped due to toxicity, followed by maintenance endocrine therapy. She achieved a sustained complete radiological and cerebrospinal fluid cytological response for over 9 years. She eventually passed away of ischaemic bowel unrelated to her cancer.

Clinical Practice Patterns in Chemotherapeutic Treatment Regimens for Metastatic Colorectal Cancer.

BACKGROUND: The treatment of patients with metastatic colorectal cancer (mCRC) has evolved during the past 2 decades, and patient survival has increased. Consequently, patients are exposed to more chemotherapeutic agents and regimens. Little is known about therapeutic drug sequencing and the factors influencing these choices. MATERIALS AND METHODS: An observational, retrospective medical record review was conducted of patients with newly diagnosed adult mCRC from January 2002 to September 2013 identified in the McGill University-Jewish General Hospital's local tumor registry. All patients presented with mCRC (stage IV) and received ≥ 2 cycles and/or ≥ 28 days of first-line chemotherapy. The patient demographics, CRC characteristics, treatment patterns, and outcomes were recorded. The reason for changing or halting therapy was also reported. RESULTS: Of the 215 patients who underwent treatment, 74.4% received second-line, 36% third-line, and 16.3% fourth-line treatment. In total, 88% received ≥ 3 classes of cytotoxic chemotherapy and 80% received ≥ 1 biologic agent. The most common first-line treatment was FOLFOX (5-fluorouracil, leucovorin, oxaliplatin) (47.4%) or CAPOX (capecitabine, oxaliplatin) (28.8%), and more than one half received bevacizumab (56%). Among the second- and third-line treatments, FOLFIRI (irinotecan, 5-fluorouracil, leucovorin) was the most common (40.3% and 30.3%, respectively), and bevacizumab was the most frequently used biologic agent (48.1% and 39.2%, respectively). For fourth-line treatment and beyond, most patients participated in clinical trials (45.7%) or received panitumumab monotherapy (31.4%). Across the first 4 therapy lines, disease progression was the primary motive for discontinuation (39.5%, 53.8%, 58.2%, and 37.1%). CONCLUSION: FOLFOX was the most common first-line and FOLFIRI the most common second- and third-line mCRC therapy. Bevacizumab was the most frequently used targeted therapy across all 3 treatment lines. Therapy discontinuation was primarily due to disease progression.

Interferon-α/ß enhances temozolomide activity against MGMT-positive glioma stem-like cells.

Glioma is one of the most common primary tumors of the central nervous system in adults. Glioblastoma (GBM) is the most lethal type of glioma, whose 5-year survival is 9.8% at best. Glioma stem-like cells (GSCs) play an important role in recurrence and treatment resistance. MGMT is a DNA repair protein that removes DNA adducts and therefore attenuates treatment efficiency. It has been reported that interferon-α/ß (IFN-α/ß) downregulates the level of MGMT and sensitizes glioma cells to temozolomide. In the present study, we assessed whether IFN-α/ß is able to sensitize GSCs to temozolomide by modulating MGMT expression. Upon the treatment of IFN-α/ß, the efficacy of temozolomide against MGMT­positive GSCs was markedly enhanced by combination treatment with IFN-α/ß when compared with the temozolomide single agent group, and MGMT expression was markedly decreased at the same time. Further mechanistic study showed that IFN-α/ß suppressed the NF-κB activity, which further mediated the sensitization of MGMT­positive GSCs to temozolomide. Our data therefore demonstrated that the application of IFN-α/ß is a promising agent with which to enhance temozolomide efficiency and reduce drug resistance, and our findings shed light on improving clinical outcomes and prolonging the survival of patients with malignant gliomas.

Simultaneous inhibition of ATR and PARP sensitizes colon cancer cell lines to irinotecan.

Enhanced DNA damage repair is one mechanism involved in colon cancer drug resistance. Thus, targeting molecular components of repair pathways with specific small molecule inhibitors may improve the efficacy of chemotherapy. ABT-888 and VE-821, inhibitors of poly-ADP-ribose-polymerase (PARP) and the serine/threonine-kinase Ataxia telangiectasia related (ATR), respectively, were used to treat colon cancer cell lines in combination with the topoisomerase-I inhibitor irinotecan (SN38). Our findings show that each of these DNA repair inhibitors utilized alone at nontoxic single agent concentrations resulted in sensitization to SN38 producing a 1.4-3 fold reduction in the 50% inhibitory concentration (IC50) of SN38 in three colon cancer cell lines. When combined together, nontoxic concentrations of ABT-888 and VE-821 produced a 4.5-27 fold reduction in the IC50 of SN38 with the HCT-116 colon cancer cells demonstrating the highest sensitization as compared to LoVo and HT-29 colon cancer cells. Furthermore, the combination of all three agents was associated with maximal G2 -M arrest and enhanced DNA-damage (γH2AX) in all three colon cancer cell lines. The mechanism of this enhanced sensitization was associated with: (a) maximal suppression of SN38 induced PARP activity in the presence of both inhibitors and (b) ABT-888 producing partial abrogation of the VE-821 enhancement of SN38 induced DNA-PK phosphorylation, resulting in more unrepaired DNA damage; these alterations were only present in the HCT-116 cells which have reduced levels of ATM. This novel combination of DNA repair inhibitors may be useful to enhance the activity of DNA damaging chemotherapies such as irinotecan and help produce sensitization to this drug in colon cancer.

Aromatase inhibition in relapsing low malignant potential serous tumours of the ovary.

Low malignant potential serous tumours (LMPSTs) of the ovary represent an indolent disease, with an excellent prognosis in a majority of patients. Patients with recurrent LMPSTs tend to develop widespread disease with a mortality rate as high as 70%. These tumours tend to have a very poor response to standard chemotherapy, and the management of primary and recurrent disease beyond surgical resection is not well defined. The majority of LMPST have been reported to express oestrogen and progesterone hormone receptors. However, only three reported cases of antihormonal treatment in this setting, and only one using aromatase inhibitors (AI), have been previously reported. We herein report long-term complete remission of two patients with relapsed, chemotherapy-resistant LMPSTs, treated with long-term AI (anastrozole 1 mg daily) as per negative MRI and positron emission tomography scans. Our results warrant further investigation for the use of AIs for metastatic recurrent LMPSTs.

Systemic cancer therapy: achievements and challenges that lie ahead.

In the last half of the century, advances in the systemic therapy of cancer, including chemotherapy, hormonal therapy, targeted therapy, and immunotherapy have been responsible for improvements in cancer related mortality in developed countries even as the population continues to age. Although such advancements have yet to benefit all cancer types, systemic therapies have led to an improvement in overall survival in both the adjuvant and metastatic setting for many cancers. With the pressure to make therapies available as soon as possible, the side-effects of systemic therapies, in particular long-term side-effects are not very well characterized and understood. Increasingly, a number of cancer types are requiring long-term and even lifelong systemic therapy. This is true for both younger and older patients with cancer and has important implications for each subset. Younger patients have an overall greater expected life-span, and as a result may suffer a greater variety of treatment related complications in the long-term, whereas older patients may develop earlier side-effects as a result of their frailty. Because the incidence of cancer in the world will increase over the next several decades and there will be more people living with cancer, it is important to have an understanding of the potential side-effects of new systemic therapies. As an introductory article, in this review series, we begin by describing some of the major advances made in systemic cancer therapy along with some of their known side-effects and we also make an attempt to describe the future of systemic cancer therapy.

Small Molecules, Inhibitors of DNA-PK, Targeting DNA Repair, and Beyond.

Many current chemotherapies function by damaging genomic DNA in rapidly dividing cells ultimately leading to cell death. This therapeutic approach differentially targets cancer cells that generally display rapid cell division compared to normal tissue cells. However, although these treatments are initially effective in arresting tumor growth and reducing tumor burden, resistance and disease progression eventually occur. A major mechanism underlying this resistance is increased levels of cellular DNA repair. Most cells have complex mechanisms in place to repair DNA damage that occurs due to environmental exposures or normal metabolic processes. These systems, initially overwhelmed when faced with chemotherapy induced DNA damage, become more efficient under constant selective pressure and as a result chemotherapies become less effective. Thus, inhibiting DNA repair pathways using target specific small molecule inhibitors may overcome cellular resistance to DNA damaging chemotherapies. Non-homologous end joining a major mechanism for the repair of double-strand breaks (DSB) in DNA is regulated in part by the serine/threonine kinase, DNA dependent protein kinase (DNA-PK). The DNA-PK holoenzyme acts as a scaffold protein tethering broken DNA ends and recruiting other repair molecules. It also has enzymatic activity that may be involved in DNA damage signaling. Because of its' central role in repair of DSBs, DNA-PK has been the focus of a number of small molecule studies. In these studies specific DNA-PK inhibitors have shown efficacy in synergizing chemotherapies in vitro. However, compounds currently known to specifically inhibit DNA-PK are limited by poor pharmacokinetics: these compounds have poor solubility and have high metabolic lability in vivo leading to short serum half-lives. Future improvement in DNA-PK inhibition will likely be achieved by designing new molecules based on the recently reported crystallographic structure of DNA-PK. Computer based drug design will not only assist in identifying novel functional moieties to replace the metabolically labile morpholino group but will also facilitate the design of molecules to target the DNA-PKcs/Ku80 interface or one of the autophosphorylation sites.

The PARP inhibitor ABT-888 synergizes irinotecan treatment of colon cancer cell lines.

Poly [ADP-ribose] polymerase-1 (PARP-1) localizes rapidly to sites of DNA damage and has been associated with various repair mechanisms including base excision repair (BER) and homologous recombination/non-homologous end joining (HRR/NHEJ). PARP-1 acts by adding poly-ADP ribose side chains to target proteins (PARylation) altering molecular interactions and functions. Recently small molecule inhibitors of PARP-1 have been shown to have significant clinical potential and third generation PARP inhibitors are currently being investigated in clinical trials. These drugs alone or in combination with radio/chemotherapy have resulted in meaningful patient responses and an increase in survival in metastatic breast cancer cases bearing BRCA-deficient or triple negative tumors and BRCA-deficient ovarian cancer patients. ABT-888, a potent PARP-1 inhibitor, sensitizes many cancer cells in-vitro and in-vivo to temozolomide. As such, we hypothesized that colon cancers would be sensitized to the DNA damaging chemotherapeutic agents, oxaliplatin and irinotecan, by ABT-888. Using colon cancer cell lines significant synergy was observed between ABT-888 and irinotecan at concentrations of ABT-888 as low as 0.125 µM. The level of synergy observed correlated with the degree of PARP1 inhibition as measured biochemically in cell lysates. ABT-888 at concentrations of 0.5-4 µM resulted in synergy with oxaliplatin. Furthermore, 24 h post treatment combinations of ABT-888/irinotecan generally resulted in increased G2/M cell cycle arrest and increased levels of DNA damage, followed by increased levels of apoptosis 48 h post treatment. In conclusion this study suggests that ABT-888 may be a clinically effective adjuvant to current colon cancer therapies that include the use of irinotecan and/or oxaliplatin.

The phosphatidylinositol-3 kinase I inhibitor BKM120 induces cell death in B-chronic lymphocytic leukemia cells in vitro.

BKM120, a pan class I PI3K inhibitor, was cytotoxic in the majority of primary B-chronic lymphocytic leukemia (CLL) lymphocytes, including samples from patients who have a high-risk for poor response to treatment (patient with del11 and del17) at clinically obtainable concentrations. The PI3Kδ inhibitor Cal-101 is cytotoxic in B-CLL lymphocytes in vitro and is active in the treatment of CLL in vivo. Interestingly, we demonstrated that BKM120 is 3.6 fold more toxic than Cal-101 in malignant B-CLL lymphocytes in vitro. BKM120 cytotoxicity correlated with the basal expression of proteins involved in the PI3K/Akt pathway. A protein signature of PI3K pathway proteins predicts the response to BKM120 treatment. In the primary B-CLL lymphocytes tested in vitro, BKM120 decreased the phosphorylation status of molecular biomarkers used as indicators of PI3K pathway inhibition in vivo. Also, BKM120 induced apoptosis in primary B-CLL cells culture in the presence and absence of stromal cell support. Our findings suggest that BKM120 should be tested clinically in CLL.

Is there an epigenetic component underlying the resistance of triple-negative breast cancers to parp inhibitors?

Poly(ADP-ribose) polymerase (Parp) is an enzyme responsible for catalyzing post-translational modifications through the addition of poly(ADP-ribose) chains (known as PARylation). Modification by PARylation modulates numerous cellular processes including transcription, chromatin remodeling, apoptosis, and DNA damage repair. In particular, the role of Parp activation in response to DNA damage has been intensely studied. Tumors bearing mutations of the breast cancer susceptibility genes, Brca1/2, are prone to DNA breakages whose restoration into functional double-strand DNA is Parp dependent. This concept has been exploited therapeutically in Brca mutated breast and ovarian tumors, where acute sensitivity to Parp inhibitors is observed. Based on in vitro and clinical studies it remains unclear to what extent Parp inhibitors can be utilized beyond treating Brca mutated tumors. This review will focus on the often overlooked roles of PARylation in chromatin remodeling, epigenetics, and transcription to explain why some cancers may be unresponsive to Parp inhibition. We predict that understanding the impact of PARylation on gene expression will lead to alternative approaches to manipulate the Parp pathway for therapeutic benefit.

Irinotecan and DNA-PKcs inhibitors synergize in killing of colon cancer cells.

This study sought to measure the degree of synergy induced by specific small molecule inhibitors of DNA-PK [NU7026 and IC486241 (ICC)], a major component of the non-homologous end-joining (NHEJ) pathway, with SN38 or oxaliplatin. Synergy between the DNA damaging drugs and the DNA-PK inhibitors was assessed using the sulforhodamine-B assay (SRB). Effects of drug combinations on cell cycle and DNA-PK activity were determined using flow cytometry and western blot analysis. DNA damage was assessed via comet assay and quantification of γH2AX. The role of homologous recombination repair (HRR) was determined by nuclear Rad51 protein levels and a GFP reporter recombination assay. Significant reductions in the IC(50) values of SN38 were observed at 5 and 10 µM of DNA-PK inhibitors. Moreover, at 1-2 µM (attainable concentrations with ICC in mice) these DNA-PKcs inhibitors demonstrated synergistic reductions in the IC(50) of SN38. Flow cytometric data indicated that SN38 and SN38 in combination with DNA-PKcs inhibitors showed dramatic G2/M arrest at 24 h. Furthermore, reduced phosphorylation of DNA-PKcs and increased DNA damage were observed at this time point with SN38 in combination with DNA-PKcs inhibitors as compared to cells treated with SN38 alone. SN38 alone and in the presence of ICC increased nuclear Rad51 protein levels. Furthermore, inhibition of DNA-PKcs increased HRR suggesting that NHEJ is a negative regulator of HRR. These data indicate that small molecule inhibitors of DNA-PKcs dramatically enhance the efficacy of SN38 in colon cancer cell lines.