Studies on a human melanoma cell line: effect of cell crowding and nutrient depletion on the biophysical and kinetic characteristics of the cells

Potentiating Oncolytic Virus-Induced Immune-Mediated Tumor Cell Killing Using Histone Deacetylase Inhibition

A clinical oncolytic herpes simplex virus (HSV) encoding granulocyte-macrophage colony-stimulating factor (GM-CSF), talimogene laherparepvec, causes regression of injected and non-injected melanoma lesions in patients and is now licensed for clinical use in advanced melanoma. To date, limited data are available regarding the mechanisms of human anti-tumor immune priming, an improved understanding of which could inform the development of future combination strategies with improved efficacy. This study addressed direct oncolysis and innate and adaptive human immune-mediated effects of a closely related HSV encoding GM-CSF (HSVGM-CSF) alone and in combination with histone deacetylase inhibition. We found that HSVGM-CSF supported activation of anti-melanoma immunity via monocyte-mediated type I interferon production, which activates NK cells, and viral maturation of immature dendritic cells (iDCs) into potent antigen-presenting cells for cytotoxic T lymphocyte (CTL) priming. Addition of the histone deacetylase inhibitor valproic acid (VPA) to HSVGM-CSF treatment of tumor cells increased viral replication, viral GM-CSF production, and oncolysis and augmented the development of anti-tumor immunity. Mechanistically, VPA increased expression of activating ligands for NK cell recognition and induced expression of tumor-associated antigens, supporting innate NK cell killing and CTL priming. These data support the clinical combination of talimogene laherparepvec with histone deacetylase inhibition to enhance oncolysis and anti-tumor immunity.

Induction of apoptosis in nutrient-deprived cultures of hybridoma and myeloma cells

In the present study, cell death was investigated in cultures of NS/0 myelomas and SP2/0-derived D5 hybridomas through morphological examination of cells stained with acridine orange and ethidium bromide. The relative contribution of elevated levels of lactic acid and ammonia, as well as deprivation of glutamine, cystine, and glucose on the induction of necrosis or apoptosis, was investigated. In batch culture of D5 hybridoma cells, induction of apoptotic cell death correlated with the exhaustion of glutamine, while in the case of NS/0 myelomas, it coincided with exhaustion of cystine. To determine whether limiting nutrients were the actual triggering factors for apoptosis in batch culture, exponentially growing cells were resuspended in glutamine or cystine-free media. Within 30 to 40 h, viability decreased to 50% and the nonviable cell population displayed typical apoptotic morphology, with crescents of condensed chromatin around the periphery of the nucleus, or with the entire nucleus present as one or a group of featureless, brightly staining spherical beads. Similarly, D5 hybridomas and NS/0 myelomas cultivated in glucose-free medium died mainly from apoptosis. Cells were also cultivated in fresh medium supplemented with elevated concentrations of ammonia (3.0 mM) and/or lactate (35 mM, 50 mM). This resulted in decreased viabilities and necrotic death in both cell lines. From these results, we conclude that D5 hybridomas and NS/0 myelomas deprived of essential nutrients die by apoptosis, whereas incubation in the presence of elevated levels of metabolic byproducts such as ammonia and lactate will induce necrotic cell death in these cells.

Tumor-immune interaction, surgical treatment, and cancer recurrence in a mathematical model of melanoma

Malignant melanoma is a cancer of the skin arising in the melanocytes. We present a mathematical model of melanoma invasion into healthy tissue with an immune response. We use this model as a framework with which to investigate primary tumor invasion and treatment by surgical excision. We observe that the presence of immune cells can destroy tumors, hold them to minimal expansion, or, through the production of angiogenic factors, induce tumorigenic expansion. We also find that the tumor–immune system dynamic is critically important in determining the likelihood and extent of tumor regrowth following resection. We find that small metastatic lesions distal to the primary tumor mass can be held to a minimal size via the immune interaction with the larger primary tumor. Numerical experiments further suggest that metastatic disease is optimally suppressed by immune activation when the primary tumor is moderately, rather than minimally, metastatic. Furthermore, satellite lesions can become aggressively tumorigenic upon removal of the primary tumor and its associated immune tissue. This can lead to recurrence where total cancer mass increases more quickly than in primary tumor invasion, representing a clinically more dangerous disease state. These results are in line with clinical case studies involving resection of a primary melanoma followed by recurrence in local metastases.

Melanoma is a deadly skin cancer that invades into the dermis and metastasizes into the surrounding tissue. In clinical cases, surgical excision of the primary tumor has led to widespread and accelerated growth in metastases. We develop a mathematical model describing the basic process of melanoma invasion, metastatic spread, and the anti-tumor immune response. This model is formulated using partial differential equations that describe the spatial and temporal evolution of a number of different cellular populations, and it uses a realistic skin geometry. Using simulations, we examine the importance of the immune response when a primary tumor is spawning satellite metastases. We find that local metastases can be suppressed by the immune response directed against the primary tumor, but grow aggressively following surgical treatment. We also find that moderately metastatic tumors optimally activate the local immune response against disseminated disease, and in this case tumor excision may have profound effects on metastatic growth. We conclude that surgical perturbation of the immune response controlling local metastases is one mechanism by which cancer can recur. This could have implications as to the appropriate clinical management of melanomas and other solid tumors.

Differentiation and assessment of cell death

Three documented cell death pathways, apoptosis, necrosis, and oncosis will be discussed. The end result of each pathway is cell death; however, the path by which death is achieved and the morphological and physiological traits of each may be strikingly distinct. Now that well characterized models have been established for particularly apoptosis, the induction pathway(s) has received much attention and the pathway pathology is beginning to be understood. Three model systems were investigated: APO-1/Fas, hypoxia, and oncosis. Cell death was induced, and during a time course sampling, a variety of methodologies, including DNA fragmentation by flow cytometry and gel electrophoresis, DNA staining, flow cytometric light scatter, transmission electron microscopy, anti-tubulin, Trypan blue, annexin V, and anti-APO2.7 were employed to monitor the cell death progress. The apoptotic pathway in the CD95-induced Jurkat cell model was further investigated using caspase inhibitor peptides and analyzed for APO2.7 antigen expression and DNA fragmentation by flow cytometry. Time course sampling characterized the cell death pathway and helped to differentiate the capabilities of the methods. The time to response and duration of the response were dependent upon cell type and method of induction. The CD95-induced Jurkat cell model showed a classical apoptotic response; however the MDA-MB-175-VII hypoxia model and the anti-5A9 induced oncosis model were not as clear. Each methodology shows advantages and disadvantages that allow the investigator to select several methods to identify, monitor, and enumerate cells with respect to cell death progression using time course studies.

Effects of hypoxia on morphological and biochemical characteristics of renal epithelial cell and tubule cultures

Apoptotic cell death plays an important role in the pathogenesis of renal atrophy in diseases of the kidney involving chronic mild ischemia. The present study constitutes an in vitro model of these diseases and assesses the modes of cell death involved after hypoxic treatment of renal epithelium. Cultures of MDCK cells or primary cultures of rat renal parenchymal tubules were treated in either a physiological or a hypoxic atmosphere. Cultures were collected before treatment and at 24 h and 48 h, for morphological and biochemical studies. Both apoptosis and necrosis were observed at significantly increased levels by 48 h of hypoxia in the MDCK cell cultures. DNA gel electrophoresis patterns supported these findings. Experiments using tubule cultures demonstrated that, during the 48 h of study, tubular epithelial cells in the center of the control tubule structures died by apoptosis, possibly as a result of mild oxygen and/or nutrient depletion. With added hypoxic treatment, however, the entire tubule structure became necrotic. Results are similar to those found during in vivo studies, thus providing in vitro models that may be developed further to define factors in the pathogenesis of some renal diseases.

Drug sensitivity of non small cell carcinoma of lung by clonogenic assay in several media

Lung tumours of non small cell pathology were cultured by clonogenic assay in several media. Culture was successful in spleen conditioned medium, but only 57% grew and low plating efficiencies (PE) meant that only 23% of the original number produced significant drug results. Comparison of rat erythrocyte lysate (REL) medium with serum free defined medium (HITES) and HITES + 10% FBS demonstrated clear enhancement of PE in REL although growth was 100% successful in all these media. Ninety-three percent of samples tested against drugs in REL produced significant results. A later comparison of REL with McCoy's 5A + rbc +/- hydrocortisone produced relatively poor culture success for these 3 media and equivocal growth patterns. Low PE was attributed to age of rats used for rbc. Vindesine and cis-platinum cytotoxicity in spleen conditioned medium were 61% and 15% sensitivity respectively. These do not concur with clinical experience but the figures for overt resistance, at 39% and 69%, correspond with expected non-responders to these regimes. Drug testing in REL produced figures correlating more closely with clinical performance at 45% sensitivity to platinum and 36% of patients sensitive to both drugs, but the vindesine sensitivity at 55% is again discrepant with performance of this drug as a single agent.

In vitro quantification of melanoma tumor cell invasion

In order to quantify the invasiveness of melanoma tumor cells in vitro, a modification of the amniotic basement membrane (BM) model, described by Liotta et al. (Cancer Letters, 11, 141, 1980), was used in combination with radiolabeled tumor cells. B16-F10 metastatic murine melanoma cells and a derived clone (B16-F10L) were prelabeled with 0.1 muCi/ml of [14C]thymidine for 20-24 h in serum-free medium at 37 degrees C. Following incubation, fetal bovine serum was added to a concentration of 5 per cent, and the cells were allowed to grow to confluency for the next 24-28 h. The labeled cells were seeded onto amniotic membranes situated in Membrane Invasion Culture System (MICS) chambers at a density of 2.5 X 10(4) per well. At various times points, radioactivity of tumor cells that completely traversed the membrane was determined using an under-the-membrane sampling method. The average percent invasion demonstrated by the B16-F10 line was 2.75 per cent, and 3.65 per cent exhibited by the B16-F10L cell line after 48-53 h in vitro. Since it was apparent that some variability in thickness existed among membrane samples, a morphological analysis was performed on five sectors of a three-inch-diameter sample from four different placentae. Differences and similarities in BM thickness within the same sector were noted by this technique and could possibly contribute to some variability observed in tumor cell invasion in this model. Another parameter examined was the proliferation of tumor cells in the upper and lower wells of the MICS chambers. By 48 h, approximately 32.1 per cent of the B16-F10 cell line as well as the clone had replicated in the upper wells associated with the BMs compared with a 32.9 per cent replication in the lower wells, which reaffirmed the viability of the tumor cells under experimental conditions and insured similarly replicating populations of cells. In order to quantify the invasiveness of radiolabeled tumor cells accurately through a biological membranous barrier, the proper concentration of cells must be used, tumor cell heterogeneity should be taken into consideration, the technique of sampling radiolabeled invasive cells should be critically analysed, and thickness of the membranous barrier should all be considered as possible important factors in the quantitative analyses.

A novel approach to the study of kinetically changing cell populations

A method is described for estimating changes in cell cycle times during periods of rapid change in proliferation rate. This method, which depends upon the interpretation of pre- and post-velocity sedimentation fractionation continuous thymidine labelling patterns, exploits the relationship between sedimentation rate and cell cycle location. By this means, cycle times can be estimated under conditions that are difficult (if not impossible) to analyse by FLM methods.

Potentiation of anchorage-independent colony formation by sodium polyanethol sulphonate

Sodium polyanethol sulphonate (SPS) when incorporated into rat erythrocyte lysate (REL) containing semi-solid agar medium at 1 mg ml-1. markedly enhanced colony formation by a number of anchorage-independent cell lines. REL usually needed to be included for the expression of SPS induced potentiation as in its absence SPS was generally cytotoxic. Studies suggested that SPS reduced the lag prior to colony initiation resulting in the earlier appearance of colonies and in a higher cloning efficiency. The effectiveness of SPS in potentiating colony formation by responsive cell lines was markedly influenced by the species of serum and to a lesser extent by differences between individual batches. Enhancement by SPS was greater with poorer foetal calf serum (FCS) batches than with better. This effect may have been partly due to SPS interfering with the action of a growth inhibiting serum component, possibly a lipoprotein. Studies in which delipidated FCS was substituted for normal FCS suggested that SPS was also able to compensate for the lack of a growth-promoting lipid component. Binding studies showed that initially 125I-SPS bound equally well at 4 degrees C and 37 degrees C with continued labelling occurring only at 37 degrees C. Autoradiography of cells labelled at 37 degrees C for 24 h revealed the presence of intracytoplasmic 125I-SPS.

Murine mammary tumour cells in vitro. II. Recruitment of quiescent cells

The development of a pure quiescent (Q) tumour cell population can be induced in three mouse mammary tumour lines (66, 67 and 68H) by nutrient deprivation. When these Q cells were removed from nutrient-deprived cultures and replated in fresh medium at a lower cell concentration within 72 hr of entering quiescence virtually all of the Q cells could re-enter the proliferating (P) state. This recruitment was characterized by an increase in cell volume, an increase in total cellular RNA, and a resumption of cell division. The length of the Q to P transition varied among the three cell lines and the depth of the quiescent state depended on the amount of time the cells had been quiescent. Once re-entry into the P compartment was completed, cell-cycle times, as estimated by the culture doubling time, were the same as the cells that had not entered the Q state, however, after 72 hr in quiescence, not all of the 66 cells could reattach after trypsinization and of those that could reattach approximately equal to 50% were incapable of either increasing their RNA levels to that of proliferating G1 cells or entering S. Clonogenicity of the nutrient-deprived Q cells in these lines decreases exponentially from time the cells enter quiescence with approximate half-times of 32, 34, and 96 hr for the 66, 68H and 67 cells, respectively. Since clonogenicity was already declining at a time when all the Q cells could re-enter the P compartment, the ability of a Q cell to form a colony is not determined solely by its capacity to re-enter the proliferating compartment.

Quantitation of chemosensitivity in acute myelocytic leukaemia

A system for the prediction of clinical response in acute myelocytic leukaemia (AML), based on inhibition of growth of colony forming cells (CFC) was studied. If the product of initial drug concentration and time of exposure (C X T) was constant, the response to adriamycin (Adr) was constant, at T values less than 48 h. No constancy of response to the phase-specific agents cytosine arabinoside (Ara-C) and 6-thioguanine (6TG) was demonstrated with constant C X T (T value range 0.25-48 h). Hence in the predictive test, a 1 h incubation with Adr was employed whilst a continuous exposure to Ara-C and 6TG, with these drugs incorporated in the agar medium, was used. The in vitro sensitivity to Adr, Ara-C and 6TG of 19 AML patients and the predictive value of several parameters of sensitivity were evaluated. 6TG sensitivity was not useful for prediction of remission. Adr sensitivity in vitro made a greater contribution to prediction of remission than did Ara-C sensitivity. Seventy-nine percent of patients were correctly classified if Adr data alone were considered. A multivariate function including Adr and Ara-C results was obtained which resulted in 84% of patients correctly classified as sensitive or resistant to the agents received in remission-induction therapy.