Macrophage Profiling in Head and Neck Cancer to Improve Patient Prognosis and Assessment of Cancer Cell-Macrophage Interactions Using Three-Dimensional Coculture Models

Tumor-associated macrophages are key components of the tumor microenvironment and play important roles in the progression of head and neck cancer, leading to the development of effective strategies targeting immune cells in tumors. Our study demonstrated the prognostic potential of a new scoring system (Macroscore) based on the combination of the ratio and the sum of the high and low densities of M1 (CD80+) and M2 (CD163+) macrophages in a series of head and neck cancer patients, including a training population (n = 54) and a validation population (n = 19). Interestingly, the Macroscore outperformed TNM criteria and p16 status, showing a significant association with poor patient prognosis, and demonstrated significant predictive value for overall survival. Additionally, 3D coculture spheroids were established to analyze the crosstalk between cancer cells and monocytes/macrophages. Our data revealed that cancer cells can induce monocyte differentiation into protumoral M2 macrophages, creating an immunosuppressive microenvironment. This coculture also induced the production of immunosuppressive cytokines, such as IL10 and IL8, known to promote M2 polarization. Finally, we validated the ability of the macrophage subpopulations to induce apoptosis (M1) or support proliferation (M2) of cancer cells. Overall, our research highlights the potential of the Macroscore as a valuable prognostic biomarker to enhance the clinical management of patients and underscores the relevance of a spheroid model in gaining a better understanding of the mechanisms underlying cancer cell-macrophage interactions.

Immune Cell Density Evaluation Improves the Prognostic Values of Staging and p16 in Oropharyngeal Cancer

The incidence of oropharyngeal cancers (OPSCCs) has continued to rise over the years, mainly due to human papillomavirus (HPV) infection. Although they were newly reclassified in the last TNM staging system, some groups still relapse and have poor prognoses. Based on their implication in oncogenesis, we investigated the density of cytotoxic and regulatory T cells, macrophages, and Langerhans cells in relation to p16 status, staging and survival of patients. Biopsies from 194 OPSCCs were analyzed for HPV by RT-qPCR and for p16 by immunohistochemistry, while CD8, FoxP3, CD68 and CD1a immunolabeling was performed in stromal (ST) and intratumoral (IT) compartments to establish optimal cutoff values for overall survival (OS). High levels of FoxP3 IT and CD1a ST positively correlated with OS and were observed in p16-positive and low-stage patients, respectively. Then, their associations with p16 and TNM were more efficient than the clinical parameters alone in describing patient survival. Using multivariate analyses, we demonstrated that the respective combination of FoxP3 or CD1a with p16 status or staging was an independent prognostic marker improving the outcome of OPSCC patients. These two combinations are significant prognostic signatures that may eventually be included in the staging stratification system to develop personalized treatment approaches.

Immunoscore Combining CD8, FoxP3, and CD68-Positive Cells Density and Distribution Predicts the Prognosis of Head and Neck Cancer Patients

We assessed immune cell infiltrates to develop an immunoscore for prognosis and to investigate its correlation with the clinical data of patients with head and neck cancer. CD8, FoxP3, and CD68 markers were evaluated by immunohistochemistry in 258 carcinoma samples and positive cells were counted in stromal and intra-tumoral compartments. The RStudio software was used to assess optimal cut-offs to divide the population according to survival while the prognostic value was established by using Kaplan–Meier curves and Cox regression models for each immune marker alone and in combination. We found with univariate analysis that the infiltration of immune cells in both compartments was predictive for recurrence-free survival and overall survival. Multivariate analysis revealed that CD8+ density was an independent prognostic marker. Additionally, the combination of CD8, FoxP3, and CD68 in an immunoscore provided a significant association with overall survival (p = 0.002, HR = 9.87). Such an immunoscore stayed significant (p = 0.018, HR = 11.17) in a multivariate analysis in comparison to tumor stage and histological grade, which had lower prognostic values. Altogether, our analysis indicated that CD8, FoxP3, and CD68 immunoscore was a strong, independent, and significant prognostic marker that could be introduced into the landscape of current tools to improve the clinical management of head and neck cancer patients.

Dealing with Macrophage Plasticity to Address Therapeutic Challenges in Head and Neck Cancers

The head and neck tumor microenvironment (TME) is highly infiltrated with macrophages. More specifically, tumor-associated macrophages (TAM/M2-like) are one of the most critical components associated with poor overall survival in head and neck cancers (HNC). Two extreme states of macrophage phenotypes are described as conducting pro-inflammatory/anti-tumoral (M1) or anti-inflammatory/pro-tumoral (M2) activities. Moreover, specific metabolic pathways as well as oxidative stress responses are tightly associated with their phenotypes and functions. Hence, due to their plasticity, targeting M2 macrophages to repolarize in the M1 phenotype would be a promising cancer treatment. In this context, we evaluated macrophage infiltration in 60 HNC patients and demonstrated the high infiltration of CD68+ cells that were mainly related to CD163+ M2 macrophages. We then optimized a polarization protocol from THP1 monocytes, validated by specific gene and protein expression levels. In addition, specific actors of glutamine pathway and oxidative stress were quantified to indicate the use of glutaminolysis by M2 and the production of reactive oxygen species by M1. Finally, we evaluated and confirmed the plasticity of our model using M1 activators to repolarize M2 in M1. Overall, our study provides a complete reversible polarization protocol allowing us to further evaluate various reprogramming effectors targeting glutaminolysis and/or oxidative stress in macrophages.

Restoring p53 Function in Head and Neck Squamous Cell Carcinoma to Improve Treatments

TP53 mutation is one of the most frequent genetic alterations in head and neck squamous cell carcinoma (HNSCC) and results in an accumulation of p53 protein in tumor cells. This makes p53 an attractive target to improve HNSCC therapy by restoring the tumor suppressor activity of this protein. Therapeutic strategies targeting p53 in HNSCC can be divided into three categories related to three subtypes encompassing WT p53, mutated p53 and HPV-positive HNSCC. First, compounds targeting degradation or direct inhibition of WT p53, such as PM2, RITA, nutlin-3 and CH1iB, achieve p53 reactivation by affecting p53 inhibitors such as MDM2 and MDMX/4 or by preventing the breakdown of p53 by inhibiting the proteasomal complex. Second, compounds that directly affect mutated p53 by binding it and restoring the WT conformation and transcriptional activity (PRIMA-1, APR-246, COTI-2, CP-31398). Third, treatments that specifically affect HPV+ cancer cells by targeting the viral enzymes E6/E7 which are responsible for the breakdown of p53 such as Ad-E6/E7-As and bortezomib. In this review, we describe and discuss p53 regulation and its targeting in combination with existing therapies for HNSCC through a new classification of such cancers based on p53 mutation status and HPV infection.

ACE2 Protein Landscape in the Head and Neck Region: The Conundrum of SARS-CoV-2 Infection

The coronavirus pandemic raging worldwide since December 2019 is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which invades human cells via the angiotensin-converting enzyme 2 (ACE2) receptor. Although it has already been identified in many organs, ACE2 expression remains largely unknown in the head and neck (HN) sphere. Thus, this study aims to investigate its protein expression in several sites of the upper aerodigestive tract in order to highlight potential routes of infection. We compared ACE2 immunohistochemical expression between 70 paraffin-embedded specimens with two different antibodies and reported the quantified expression in each histological location. Surprisingly, we obtained different results depending on the antibody, an absence of labeling having been observed with a monoclonal antibody raised against the extracellular domain, whereas the polyclonal, against the cytoplasmic part of the protein, revealed enriched ACE2 expression, particularly in sinuses, vocal cords, salivary glands and oral cavity epithelial cells. The interpretation of these discordant results has brought several exciting lines of reflection. In conclusion, this study provides possible routes of entry for the SARS-CoV-2 in HN region and, above all, has led us to encourage caution when studying the ACE2 expression which is currently at the center of all attention.

HPV Involvement in the Tumor Microenvironment and Immune Treatment in Head and Neck Squamous Cell Carcinomas

Head and neck squamous cell carcinomas (HNSCC) are one of the most prevalent cancers worldwide. Active human papillomavirus (HPV) infection has been identified as an important additional risk factor and seems to be associated with a better prognosis in non-drinker and non-smoker young patients with oropharyngeal SCC. The better response of the immune system against the HPV-induced HNSCC is suspected as a potential explanation for the better prognosis of young patients. To further assess this hypothesis, our review aims to shed light the current knowledge about the impact of HPV infection on the immune response in the context of HNSCC, focusing on the innate immune system, particularly highlighting the role of macrophages, Langerhans and myeloid cells, and on the adaptative immune system, pointing out the involvement of T regulatory, T CD8 and T CD4 lymphocytes. In addition, we also review the preventive (HPV vaccines) and therapeutic (checkpoint inhibitors) strategies against HPV-related HNSCC, stressing the use of anti-CTLA4, PD-L1, PD-L2 antibodies alone and in combination with other agents able to modulate immune responses.

Impact of HPV Infection on the Immune System in Oropharyngeal and Non-Oropharyngeal Squamous Cell Carcinoma: A Systematic Review

Objectives: To review the current knowledge regarding the involvement of human papilloma virus (HPV) infection and the immune system in the development of head and neck squamous cell carcinoma (HNSCC). Methods: An electronic literature search was conducted to identify articles published between 1990 and 2019 pertaining to tumor-infiltrating immune cells (TICs) in HNSCC using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Issues of clinical relevance, including tumor location, the number of tumor samples, the inclusion of additional specimens (dysplastic or normal mucosa), tumor size, methods used for HPV detection, relationship between antigen expression and patient characteristics (age, gender, smoking, alcohol consumption, etc.), and prognostic data (overall survival (OS) and recurrence-free survival (RFS)) were assessed by four blinded investigators. Results: The search identified 335 relevant studies, of which 41 met the inclusion criteria. Of these, 7 studies focused on the peripheral blood immune cell concentration in patients with HNSCC according to HPV status, and 36 studies investigated TICs in the intraepithelial and/or stromal compartment(s) according to HPV status. The immune cells studied were CD8+ T cells (N = 19), CD4+ T cells (N = 7), regulatory T cells (Tregs, N = 15), macrophages (N = 13), myeloid-derived suppressor cells (MDSCs, N = 4), and Langerhans cells (LCs, N = 2). Conclusions: Irrespective of tumor location, CD8+ and CD4+ T cells appear to play a key role in the development of HPV−related HNSCC, and their infiltration is likely associated with a significant impact on OS and RFS. To date, the roles and prognostic value of Tregs, macrophages, DCs and MDSCs remain unclear.

Infiltration of FoxP3+ Regulatory T Cells is a Strong and Independent Prognostic Factor in Head and Neck Squamous Cell Carcinoma

Head and Neck Squamous Cell Carcinomas (HNSCC) are characterized by a large heterogeneity in terms of the location and risk factors. For a few years now, immunotherapy seems to be a promising approach in the treatment of these cancers, but a better understanding of the immune context could allow to offer a personalized treatment and thus probably increase the survival of HNSCC patients. In this context, we evaluated the infiltration of FoxP3+ Tregs on 205 human formalin-fixed paraffin-embedded HNSCC and we assessed its prognostic value compared to other potential prognostic factors, including HPV infection. First, we found a positive correlation of FoxP3+ Treg infiltration between the intra-tumoral (IT) and the stromal (ST) compartments of the tumors (p < 0.0001). A high infiltration of these cells in both compartments was associated with longer recurrence-free (ST, RFS, p = 0.007; IT, RFS, p = 0.019) and overall survivals (ST, OS, p = 0.002; ST, OS, p = 0.002) of HNSCC patients. Early tumor stage (OS, p = 0.002) and differentiated tumors (RFS, p = 0.022; OS, p = 0.043) were also associated with favorable prognoses. Multivariate analysis revealed that FoxP3+ Treg stromal infiltration, tumor stage and histological grade independently influenced patient prognosis. In conclusion, the combination of these three markers seem to be an interesting prognostic signature for HNSCC.

Involvement of HPV Infection in the Release of Macrophage Migration Inhibitory Factor in Head and Neck Squamous Cell Carcinoma

Human papilloma virus (HPV) infection has been well-established as a risk factor in head and neck squamous cell carcinoma (HNSCC). The carcinogenic effect of HPV is mainly due to the E6 and E7 oncoproteins, which inhibit the functions of p53 and pRB, respectively. These oncoproteins could also play a role in the Warburg effect, thus favoring tumor immune escape. Here, we demonstrated that the pro-inflammatory cytokine macrophage migration inhibitory factor (MIF) is expressed at higher levels in HPV-negative patients than in HPV-positive patients. However, the secretion of MIF is higher in HPV-positive human HNSCC cell lines, than in HPV-negative cell lines. In-HPV positive cells, the half inhibitory concentration (IC50) of MIF inhibitor (4-iodo-6-phenylpyrimidine (4-IPP)) is higher than that in HPV-negative cells. This result was confirmed in vitro and in vivo by the use of murine SCCVII cell lines expressing either E6 or E7, or both E6 and E7. Finally, to examine the mechanism of MIF secretion, we conducted proton nuclear magnetic resonance (¹H-NMR) experiments, and observed that lactate production is increased in both the intracellular and conditioned media of HPV-positive cells. In conclusion, our data suggest that the stimulation of enzymes participating in the Warburg effect by E6 and E7 oncoproteins increases lactate production and hypoxia inducible factor 1α (HIF-1α) expression, and finally induces MIF secretion.

Whole-exon sequencing of human myeloma cell lines shows mutations related to myeloma patients at relapse with major hits in the DNA regulation and repair pathways

Background

Human myeloma cell lines (HMCLs) are widely used for their representation of primary myeloma cells because they cover patient diversity, although not fully. Their genetic background is mostly undiscovered, and no comprehensive study has ever been conducted in order to reveal those details.

Methods

We performed whole-exon sequencing of 33 HMCLs, which were established over the last 50 years in 12 laboratories. Gene expression profiling and drug testing for the 33 HMCLs are also provided and correlated to exon-sequencing findings.

Results

Missense mutations were the most frequent hits in genes (92%). HMCLs harbored between 307 and 916 mutations per sample, with TP53 being the most mutated gene (67%). Recurrent bi-allelic losses were found in genes involved in cell cycle regulation (RB1, CDKN2C), the NFκB pathway (TRAF3, BIRC2), and the p53 pathway (TP53, CDKN2A). Frequency of mutations/deletions in HMCLs were either similar to that of patients (e.g., DIS3, PRDM1, KRAS) or highly increased (e.g., TP53, CDKN2C, NRAS, PRKD2). MAPK was the most altered pathway (82% of HMCLs), mainly by RAS mutants. Surprisingly, HMCLs displayed alterations in epigenetic (73%) and Fanconi anemia (54%) and few alterations in apoptotic machinery. We further identified mutually exclusive and associated mutations/deletions in genes involved in the MAPK and p53 pathways as well as in chromatin regulator/modifier genes. Finally, by combining the gene expression profile, gene mutation, gene deletion, and drug response, we demonstrated that several targeted drugs overcome or bypass some mutations.

Conclusions

With this work, we retrieved genomic alterations of HMCLs, highlighting that they display numerous and unprecedented abnormalities, especially in DNA regulation and repair pathways. Furthermore, we demonstrate that HMCLs are a reliable model for drug screening for refractory patients at diagnosis or at relapse.

Electronic supplementary material

The online version of this article (10.1186/s13045-018-0679-0) contains supplementary material, which is available to authorized users.

High stromal Foxp3-positive T cell number combined to tumor stage improved prognosis in head and neck squamous cell carcinoma

OBJECTIVES

Head and neck squamous cell carcinomas (HNSCC), one of the most frequent cancers in the world, are largely infiltrated by inflammatory immune cells. Our aim was to evaluate the number of Foxp3+ T cells in HNSCC, reporting its prognostic power in comparison to other risk factors.

MATERIAL AND METHODS

Our clinical series was composed of 21 tumor-free peri-tumoral epithelia, 49 low grade dysplasia, 43 high grade dysplasia and 110 carcinoma samples including some cases with HPV infection. In vivo experiments were conducted on 80 C3H/HeN mice which were orthotopically injected with SCCVII CT, E7, E6 and E6/E7 cell lines.

RESULTS

Foxp3+ T cell infiltration increased with tumor progression from normal epithelia, dysplasia to carcinoma and the increase is more important in HPV+ patients than in negative ones. Animal experiments revealed that E7 oncoprotein expression was significantly associated with an increase in Foxp3+ T cell recruitment in tumor, a delay in tumor onset and improved animal survival. Univariate Cox regression analyses demonstrated that high Foxp3+ T cell number in stromal compartment is associated with longer patient recurrence-free and overall survivals. Foxp3+ T cell number improved the prognostic value of tumor stage. Multivariate analyses reported that stromal Foxp3+ T cell number is a strong prognostic factor independent of classical risk factors such as tobacco, alcohol, and HPV status.

CONCLUSION

Foxp3+ T cell number is a significant prognostic factor for HNSCC, improving the tumor stage, and that viral E7 may play a role in the Foxp3+ T cell infiltration to the tumor.

High infiltration of CD68+ macrophages is associated with poor prognoses of head and neck squamous cell carcinoma patients and is influenced by human papillomavirus

Incidence of human papillomavirus (HPV)-related head and neck squamous cell carcinomas (HNSCCs) has increased over the last few decades. The reaction of the host immune system to these tumors remains biologically complex. Here, we investigated CD68+ macrophage numbers, reporting the prognostic value in comparison to other risk factors. We also examined CD68+ macrophage infiltration during disease progression regarding the impact of HPV infection, and we studied the role of HPV16-E6/E7 oncoproteins in CD68+ macrophage recruitment. CD68+ macrophage numbers were evaluated in 10 cases of tumor-free peri-tumoral epithelia, 43 cases of low-grade dysplasia, 45 cases of high-grade dysplasia and 110 cases of carcinoma. Our in vivo model was developed in 80 C3H/HeN mice orthotopically injected with HPV16-E6, -E7 or -E6/E7-transfected SCC-VII cell lines. High CD68+ macrophage numbers in the intra-tumoral compartment were associated with shorter patient survival (recurrence-free survival: p = 0.001; overall survival: p = 0.01). Multivariate analyses reported that CD68+ macrophage infiltration and tumor stage were strong and independent prognostic factors of HNSCC. CD68+ macrophage numbers increased during HNSCC progression both in intra-epithelial (p < 0.001) and stromal compartments (p < 0.001). A higher density of CD68+ macrophages was observed in advanced stages (p = 0.004). Patients with transcriptionally active HPV infections had higher CD68+ macrophage density than did HPV-negative patients (p = 0.003). CD68+ macrophage infiltration was higher in HPV-E7+ and −E6/E7+ mouse tumors than in -E6+ tumors (p = 0.029 and p < 0.001). In conclusion, the extent of CD68+ macrophage infiltration is a significant prognostic factor for HNSCC patients. The recruitment of macrophages increases during disease progression and is influenced by the HPV virus.

Decitabine and Melphalan Fail to Reactivate p73 in p53 Deficient Myeloma Cells

(1) Background: TP53 deficiency remains a major adverse event in Multiple Myeloma (MM) despite therapeutic progresses. As it is not possible to target TP53 deficiency with pharmacological agents, we explored the possibility of activating another p53 family member, p73, which has not been well studied in myeloma. (2) Methods: Using human myeloma cell lines (HMCLs) with normal or abnormal TP53 status, we assessed TP73 methylation and expression. (3) Results: Using microarray data, we reported that TP73 is weakly expressed in 47 HMCLs and mostly in TP53 wild type (TP53^wt) HMCLs (p = 0.0029). Q-RT-PCR assays showed that TP73 was expressed in 57% of TP53^wt HMCLs (4 out of 7) and 11% of TP53 abnormal (TP53^abn) HMCLs (2 out of 18) (p = 0.0463). We showed that TP73 is silenced by methylation in TP53^abn HMCLs and that decitabine increased its expression, which, however, remained insufficient for significant protein expression. Alkylating drugs increased expression of TP73 only in TP53^wt HMCLs but failed to synergize with decitabine in TP53^abn HMCLs. (4) Conclusions: Decitabine and melphalan does not appear as a promising combination for inducing p73 and bypassing p53 deficiency in myeloma cells.

Langerhans cell number is a strong and independent prognostic factor for head and neck squamous cell carcinomas

OBJECTIVES

Head and neck squamous cell carcinomas (HNSCCs) exhibit great biological heterogeneity and relatively poor prognosis. Tobacco and alcohol consumption is involved in the cause of the majority of these cancers, but over the last several years, Human Papilloma Virus (HPV) infection has increased specifically in oropharyngeal cancers and become an additional risk factor. Here, we evaluated the number of Langerhans cells (LCs) in HNSCC and reporting its prognostic power in comparison to other risk factors.

MATERIALS AND METHODS

Our clinical series was composed of 25 tumor-free peritumoral epithelium, 64 low-grade dysplasia, 54 high-grade dysplasia and 125 carcinoma samples. HPV was detected by E6/E7 qPCR and p16 immunohistochemistry. CD1a-positive LCs were counted in intra-tumoral and stromal compartments as well as lymph nodes. MIP-3α was assessed in carcinomas using immunohistochemistry.

RESULTS

Univariate Cox regression analyses demonstrated that high LC number is associated with longer recurrence-free survival in both intra-tumoral and stromal compartments and longer overall survival in stromal compartment. Tobacco and alcohol habits, but not HPV status, are also correlated with poor prognoses in terms of recurrence. Multivariate analyses reported stromal LC number as a strong prognostic factor independent of tobacco, alcohol and HPV status. Moreover, LC number is higher in tumors and invaded lymph nodes than dysplastic lesions but it decreases in HPV-positive cancer patients. Further, LC number correlates with MIP-3α expression.

CONCLUSION

These findings suggest that LC number is a significant and independent prognostic factor for HNSCC. LC infiltration is increased in cancer lesions but decrease with HPV infection.

Classical risk factors, but not HPV status, predict survival after chemoradiotherapy in advanced head and neck cancer patients

Purpose

Despite the advent of concomitant chemoradiotherapy (CCRT), the prognosis of advanced head and neck squamous cell carcinoma (HNSCC) patients remains particularly poor. Classically, HNSCC, especially oropharyngeal carcinomas, associated with human papillomavirus (HPV) exhibits better treatment outcomes than HNSCCs in non-infected patients, eliciting a call for the de-escalation of current therapies. To improve the management of HNSCC patients, we aimed to determine the impact of active HPV infection on patient response, recurrence and survival after CCRT in a population of heavy tobacco and alcohol consumers.

Methods

Paraffin-embedded samples from 218 advanced HNSCC patients, mostly smokers and/or drinkers treated by CCRT, were tested for the presence of HPV DNA by surrogate type-specific E6/E7 qPCR and p16 immunohistochemistry. Associations between the response to CCRT and patient outcomes according to HPV status and clinical data were evaluated by Kaplan–Meier analysis and both univariate and multivariate Cox regression.

Results

Type-specific E6/E7 PCR demonstrated HPV positivity in 20 % of HNSCC. Regarding HPV status, we did not find any significant relation with response to therapy in terms of progression-free survival or overall survival. However, we observed a significantly worse prognosis for consumers of alcohol and tobacco compared to nondrinkers (p = 0.003) and non-smokers (p = 0.03). Survival analyses also revealed that the outcome is compromised in stage IV patients (p = 0.007) and, in particular, for oral cavity, hypopharynx and oropharynx carcinoma patients (p = 0.001).

Conclusion

The risk of death from HNSCC significantly increases when patients are exposed to tobacco and alcohol during their therapy, regardless of HPV status.

Heat shock factor 1 is a potent therapeutic target for enhancing the efficacy of treatments for multiple myeloma with adverse prognosis

Deregulated expression of heat shock proteins (HSPs) encoding genes is frequent in multiple myeloma. HSPs, which are molecular chaperones involved in protein homeostasis pathways, have emerged recently as promising therapeutic targets. Using human myeloma cell lines and primary myeloma cells belonging to various molecular groups, we tested the efficacy of HSP90, HSP70, and heat shock factor 1 (HSF1) inhibitors alone or associated with current antimyeloma drugs. We report here that KNK-437 (an inhibitor of HSF1) and bortezomib have additive effects on apoptosis induction in cells belonging to groups with bad prognosis.

RITA (Reactivating p53 and Inducing Tumor Apoptosis) is efficient against TP53abnormal myeloma cells independently of the p53 pathway

Background

The aim of this study was to evaluate the efficacy of the p53-reactivating drugs RITA and nutlin3a in killing myeloma cells.

Methods

A large cohort of myeloma cell lines (n = 32) and primary cells (n = 21) was used for this study. This cohort contained cell lines with various TP53 statuses and primary cells with various incidences of deletion of chromosome 17. Apoptosis was evaluated using flow cytometry with Apo2.7 staining of the cell lines or via the loss of the myeloma-specific marker CD138 in primary cells. Apoptosis was further confirmed by the appearance of a subG1 peak and the activation of caspases 3 and 9. Activation of the p53 pathway was monitored using immunoblotting via the expression of the p53 target genes p21, Noxa, Bax and DR5. The involvement of p53 was further studied in 4 different p53-silenced cell lines.

Results

Both drugs induced the apoptosis of myeloma cells. The apoptosis that was induced by RITA was not related to the TP53 status of the cell lines or the del17p status of the primary samples (p = 0.52 and p = 0.80, respectively), and RITA did not commonly increase the expression level of p53 or p53 targets (Noxa, p21, Bax or DR5) in sensitive cells. Moreover, silencing of p53 in two TP53^mutated cell lines failed to inhibit apoptosis that was induced by RITA, which confirmed that RITA-induced apoptosis in myeloma cells was p53 independent. In contrast, apoptosis induced by nutlin3a was directly linked to the TP53 status of the cell lines and primary samples (p < 0.001 and p = 0.034, respectively) and nutlin3a increased the level of p53 and p53 targets in a p53-dependent manner. Finally, we showed that a nutlin3a-induced DR5 increase (≥1.2-fold increase) was a specific and sensitive marker (p < 0.001) for a weak incidence of 17p deletion within the samples (≤19%).

Conclusion

These data show that RITA, in contrast to nutlin3a, effectively induced apoptosis in a subset of MM cells independently of p53. The findings and could be of interest for patients with a 17p deletion, who are resistant to current therapies.

Detection and quantification of human papillomavirus in benign and malignant parotid lesions

BACKGROUND/AIM

Human papillomavirus (HPV) is implicated in head and neck squamous cell carcinomas. However, the causal role of HPV in carcinomas of the parotid gland remains uncertain and less documented. This study aimed to determine the potential implication of HPV in the development of benign and malignant lesions of the parotid gland.

MATERIALS AND METHODS

Paraffin-embedded biopsies were obtained from 40 patients with benign parotid gland tumors and from 39 patients with parotid gland carcinomas. The 79 samples were evaluated for the presence of HPV DNA using both GP5+/GP6+ consensus Polymerase Chain Reaction (PCR) and type-specific E6/E7 PCR to detect 18 HPV types.

RESULTS

Our results showed a low prevalence of HPV, with only three HPV-positive cases among the 40 benign tumors and one infected carcinoma in the malignant population.

CONCLUSION

No association between the presence of HPV DNA and the development of parotid gland tumors was found in our study.

Cell death via DR5, but not DR4, is regulated by p53 in myeloma cells

Myeloma cells are sensitive to TRAIL through the two death receptors DR4 and DR5. Because p53 directly modulates expression of death receptors, we investigated here whether p53 can modulate myeloma sensitivity to TRAIL. We found that p53 affects the sensitivity of myeloma cells to the DR5 agonistic human antibody lexatumumab but not the DR4 antibody mapatumumab. TP53 wild-type myeloma cells overexpressed DR5 in correlation with sensitivity to lexatumumab. Both nongenotoxic (nutlin-3a) and genotoxic (melphalan) p53-inducing stresses increased DR5 expression only in TP53 wild-type cells and synergistically increased lexatumumab efficiency yet did not increase DR4 expression, nor sensitivity to mapatumumab. Silencing of p53 strongly decreased DR5 expression and induced resistance to nutlin-3a and lexatumumab but did not modulate DR4 expression or sensitivity to mapatumumab. Increase of lexatumumab efficiency induced by nutlin-3a was related to a p53-dependent increase of DR5 expression. In primary myeloma cells, nutlin-3a increased DR5 expression and lexatumumab efficiency but did not increase mapatumumab efficiency. Taken together, our findings indicate that p53 controls the sensitivity of myeloma through DR5 but not DR4 and suggest that a subset of patients with multiple myeloma may benefit from DR5 therapy.

Human papillomavirus DNA strongly correlates with a poorer prognosis in oral cavity carcinoma

OBJECTIVES/HYPOTHESIS

The prevalence of human papillomavirus (HPV) in a clinical series of 162 patients with oral squamous cell carcinoma (OSCC) was studied. Furthermore, we analyzed the correlation between the immunohistochemical expression of p16, p53, epidermal growth factor receptor (EGFR), and HPV status to predict survival in OSCC patients.

STUDY DESIGN

Retrospective study.

METHODS

Paraffin-embedded samples from OSCC patients (n = 162) were evaluated for the presence of HPV DNA using both GP5+/GP6+ consensus polymerase chain reaction (PCR) and type-specific E6/E7 PCR to detect HPV types 6, 11, 16, 18, 31, 33, 35, 39, 45, 51, 52, 53, 56, 58, 59, 66, 67, and 68. Immunohistochemical staining for p16, p53, and EGFR was also performed.

RESULTS

The type-specific E6/E7 PCR demonstrated that 65 of the 147 OSCC patients (44%) presented with high-risk (hr) HPV types and that 38 of the 147 OSCC patients (26%) presented with low-risk (lr) HPV types. Comparable p53 and EGFR expression levels were observed in the hr HPV+ group (41.5% p53+, 92% EGFR+) and the lr HPV+ group (57% p53+, 92% EGFR+). Conversely, a slight increase in the proportion of p16+ tumors was observed in the hr HPV+ group (65%) compared with the lr HPV+ group (44%). In regard to patient outcome, the presence of HPV was correlated with a worse prognosis (P = .007).

CONCLUSIONS

A high prevalence of hr and lr HPV infections was detected in the OSCC patients included in the study. Moreover, hr HPV positivity was correlated with a decreased 5-year disease-free survival rate compared with HPV- and lr HPV+.

Critical role of the NOTCH ligand JAG2 in self-renewal of myeloma cells

The purpose of this study was to identify the pathways associated with the ability of CD138(+) human myeloma cells to form colonies in a serum-free semi-solid human collagen-based assay. Only 26% (7 of 27) of human myeloma cell lines were able to spontaneously form colonies. This spontaneous clonogenic growth correlated with the expression of the NOTCH ligand JAG2 (p<0.001). Blocking JAG-NOTCH interactions with NOTCH-Fc chimeric molecules impaired self-colony formation, indicating a role for JAG-NOTCH pathway in colony formation. In two cell lines, silencing of JAG2 blocked both colony formation and in vivo tumor formation in immunocompromised mice. RT-PCR and flow cytometry analysis revealed that JAG2 is often expressed by CD138(+) primary cells. Our results indicate that spontaneous clonogenic growth of myeloma cells requires the expression of JAG2.

TLR9 ligand induces the generation of CD20+ plasmablasts and plasma cells from CD27+ memory B-cells

Plasma cells (PCs) have a heterogeneous phenotype in humans. While bone marrow PCs are CD20-CD138+, tonsil PCs are CD20+CD138+/- and peripheral plasmablasts (PBs) are CD20-CD138-. In vitro, PCs are mainly generated by the activation of CD27+ memory B-cells through transient stimulation of CD40, and their phenotype appears similar to that of bone marrow PCs. While CD20 expression is lost at the plasmablastic stage, CD138 expression appears only at the PC stage. Thus, the CD20+CD138± phenotype of tonsil PCs does not represent an intermediate stage in the differentiation of memory B-cells into PCs. Because it has been previously shown that TLR9 activation was more able than CD40 stimulation to induce the differentiation of IgM+ CD27+ B-cells, we wondered whether TLR9 or CD40 stimulation would induce the same phenotype of PCs. Thus, we compared the differentiation of CD27+ B-cells isolated from either the tonsils or peripheral blood and stimulated with either CD40L-expressing fibroblasts or a TLR9 ligand, CpG oligodeoxynucleotide (CpG ODN). We observed that CpG ODN mainly induced CD27+ B-cell differentiation into CD20+CD38+CD138- PBs and CD20+CD38+CD138± PCs, which appear similar to tonsil PCs. Removal of CpG ODN during differentiation induced a decrease in the CD20+ plasmablastic population, and, conversely, stimulation of CD40L-induced pre-plasmablasts with CpG ODN increased the population of CD20+CD38+ PBs. Analysis of Ig secretion showed that CpG ODN induced increased IgM secretion compared to CD40L. PCs from patients with multiple myeloma, the malignant counterpart of bone marrow PCs, rarely express CD20. We show that CpG ODN did not induce or increase CD20 in nine IgG or IgA myeloma cell lines. These data strongly suggest that CpG ODN mainly targets CD27+ IgM+ B-cells.

High prevalence of high-risk human papillomavirus in palatine tonsils from healthy children and adults

OBJECTIVE

The aim of this study was to determine the prevalence of human papillomavirus (HPV) in 80 tumor-free tonsils from healthy children and adults using a sensitive E6/E7 type-specific polymerase chain reaction (PCR).

STUDY DESIGN

Cross-sectional study.

SETTING

Ear, nose, and throat department, university hospital.

SUBJECTS AND METHODS

Paraffin-embedded tissues from tumor-free tonsils (TFTs) were evaluated for HPV DNA using GP5+/6+ consensus PCR and subsequent genotyping using E6/E7 type-specific PCR for HPV types 6, 11, 16, 18, 31, 33, 35, 39, 45, 51, 52, 53, 56, 58, 59, 66, and 68. The immunohistochemical expression of p16 and p53 was also assessed.

RESULTS

In 80 TFTs, the authors identified 10 (12.5%) that tested positive for the following high-risk HPV types: HPV 16 (8 cases), 18 (1 case), and 31 (1 case). Twelve patients (15%) tested positive for HPV infection using the GP5+/GP6+ consensus primers but were negative using quantitative PCR. These patients were considered infected with low-risk HPV types. Fifty-eight TFTs (72.5%) tested negative for both GP5+/GP6+ and type-specific HPV PCR analysis (HPV negative). Among patients infected with HPV, the authors observed a slight increase in frequency with age.

CONCLUSION

In TFTs, oncogenic and nononcogenic HPVs were present at a relatively high frequency in children and adults. The presence of high-risk HPV DNA in young children supports the horizontal transmission hypothesis and argues in favor of HPV vaccination at birth.

High incidence of high-risk HPV in benign and malignant lesions of the larynx

The aim of this study was to determine the prevalence of human papillomavirus (HPV) in patients with laryngeal benign lesions (LBLs) and laryngeal squamous cell carcinomas (LSCCs) using a sensitive E6/E7 type-specific PCR. Paraffin-embedded samples from LBL (n=39) and LSCC patients (n=67) were evaluated for the presence of HPV DNA by GP5+/GP6+ consensus PCR and E6/E7 type-specific PCR for HPV types 6, 11, 16, 18, 31, 33, 35, 39, 45, 51, 52, 53, 56, 58, 59, 66 and 68. In LSCCs, immunohistochemical staining of p16, p53 and EGFR was also assessed. The E6/E7 type-specific PCR showed that 44 out of 59 LSCC patients (i.e., 75%) had high-risk (hr) HPV types and that 27 out of 35 LBL patients (i.e., 77%) had hrHPV types. HPV-16 viral load was significantly higher in LSCC than in LBL patients (p<10-6). The presence of hrHPV DNA did not correlate with the proportion of disease-free patients. Comparable levels of p16, p53 and EGFR expression were observed in the hrHPV+ tumor group (100% p16+, 56% p53+ and 97% EGFR+) and in the HPV- or low-risk (lr) HPV+ tumor group (92% p16+, 66% p53+ and 100% EGFR+). A very high prevalence of oncogenic HPV-16 was found in a series of benign and malignant laryngeal lesions. LSCC appears to be characterized by an active hrHPV infection. In LSCCs, the hrHPV+ subgroup had a similar prognosis (in terms of risk of recurrence) as the HPV- subgroup.

A high-risk signature for patients with multiple myeloma established from the molecular classification of human myeloma cell lines

BACKGROUND

Multiple myeloma is a plasma-cell tumor with heterogeneity in molecular abnormalities and treatment response.

DESIGN AND METHODS

We have assessed whether human myeloma cell lines have kept patients' heterogeneity using Affymetrix gene expression profiling of 40 human myeloma cell lines obtained with or without IL6 addition and could provide a signature for stratification of patient risk.

RESULTS

Human myeloma cell lines, especially those derived in the presence of IL6, displayed a heterogeneity that overlaps that of the patients with multiple myeloma. Human myeloma cell lines segregated into 6 groups marked by overexpression of MAF, MMSET, CCND1, FRZB with or without overexpression of cancer testis antigens (CTA). Cell lines of CTA/MAF and MAF groups have a translocation involving C-MAF or MAFB, cell lines of groups CCND1-1 and CCND1-2like have a t(11;14) and cell lines of group MMSET have a t(4;14). The CTA/FRZB group comprises cell lines that had no or no recurrent 14q32 translocation. Expression of 248 genes accounted for human myeloma cell line molecular heterogeneity. Human myeloma cell line heterogeneity genes comprise genes with prognostic value for survival of patients making it possible to build a powerful prognostic score involving a total of 13 genes.

CONCLUSIONS

Human myeloma cell lines derived in the presence of IL6 recapitulate the molecular diversity of multiple myeloma that made it possible to design, using human myeloma cell line heterogeneity genes, a high-risk signature for patients at diagnosis. We propose this classification to be used when addressing the physiopathology of multiple myeloma with human myeloma cell lines.

IL-21 stimulates human myeloma cell growth through an autocrine IGF-1 loop

IL-21 is a member of the type I cytokine family related most closely to IL-2 and IL-15. IL-21 is a pleiotropic cytokine, produced by T, NKT, and dendritic cells, which modulates lymphoid and myeloid cell functions. Besides its activities on normal lymphoid cells, it has been shown that IL-21 is a growth factor for myeloma cells. In the present study, we demonstrate that IL-21 generated myeloma colonies from 9 of 24 human myeloma cell lines (HMCL) in a collagen-based assay. Of major interest, the capacity of IL-21 to stimulate clonogenicity was restricted to CD45(-) HMCL. We found that IL-21 induced tyrosine phosphorylation of STAT-3, STAT-1, and Erk1/2. Interestingly, an Akt activation was observed lately after 30 min to 1 h of IL-21 stimulation, indicating that this Akt phosphorylation could be due to an IGF-1 autocrine loop. This hypothesis was sustained both by the fact that IL-21 treatment induced an IGF-1 mRNA synthesis and that an antagonistic anti-IGF-1 receptor mAb (AVE1642) strongly inhibits the IL-21-induced clonogenicity. Thus, we demonstrated by quantitative PCR that IL-21 induced clonogenicity through an autocrine IGF-1 secretion in HMCL and primary myeloma cells. Because we have previously demonstrated that CD45 phosphatase inhibits the IGF-1 signaling, this inhibitory effect of CD45 explains why the IL-21-induced clonogenicity was restricted to CD45(-) HMCL. These results support that therapy against IGF-1R, which are presently under investigation in multiple myeloma, could be beneficial, not only to suppress IGF-1-mediated myeloma cell growth, but also IL-21-mediated myeloma cell growth.

Crucial role of phosphatase CD45 in determining signaling and proliferation of human myeloma cells

In multiple myeloma, a large number of growth factors (IL-6, IGF-1, FGF, HGF and HB-EGF) are involved in promoting myeloma cell growth. In the present study, a serum-free, cytokine-free, collagen-based assay, which does not allow the generation of spontaneous myeloma colonies, was used to identify the clonogenic growth factors for fourteen myeloma cell lines. IL-6 is the only clonogenic factor able to stimulate both CD45+ and CD45- myeloma cell lines, generating myeloma colonies from 10 out of 14 myeloma cell lines. Using a pharmacological Erk inhibitor, we show that the Erk/MAPK pathway is involved in IL-6-induced clonogenicity of CD45+, but not CD45- myeloma cell lines. In contrast to IL-6, the other growth factors (IGF-1, FGF, HGF and HB-EGF) stimulate only some myeloma cell lines, but always CD45-, and less effectively than IL-6. Among them, IGF-1 is the most potent, generating myeloma colonies from five out of eight CD45- myeloma cell lines. Finally, the capacity of IGF-1 and FGF to stimulate the clonogenicity of CD45- myeloma cells correlates with their ability to stimulate the Erk/MAPK pathway. We conclude that CD45 expression plays a crucial role in determining signaling and proliferation of human myeloma cell responses to IL-6, IGF-1 and other growth factors. The poor outcome of CD45- myeloma patients could be related to the capacity of CD45-myeloma cells to take advantage of multiple growth factors.

Pathogen-associated molecular patterns are growth and survival factors for human myeloma cells through Toll-like receptors

Multiple myeloma (MM) patients are strongly vulnerable to infections, which remain a major cause of death. During infection, human immune cells sense the presence of invading pathogens through the Toll-like receptor family (TLR), which recognizes pathogen-associated molecular patterns (PAMP). We hypothesized that MM cells also could sense the presence of microorganisms, thus promoting myeloma disease progression. Here, we report that human myeloma cell lines (HMCL) and primary myeloma cells express a broad range of TLR, and are sensitive to the corresponding PAMP. Toll-like receptor 1, 7 and 9 are most frequently expressed by HMCL. The expression pattern of TLR does not correlate with the one of B cells, as TLR2 and 10 are lost while TLR3, 4 and 8 are acquired by some HMCL. Culture with TLR7- and TLR9-ligands saves HMCL from serum-deprivation or dexamethasone-induced apoptosis. Similarly, both ligands increase myeloma cell growth. These effects are mediated by an autocrine secretion of interleukin-6 (IL-6) since the neutralization of IL-6 blocks the growth and survival of HMCL. Thus, TLR expression and function are not restricted to the cells of the immune system and could be of advantage for cancer cells. In MM, recurrent infections could promote tumor growth and favor escape from standard therapies.

CD45negbut Not CD45posHuman Myeloma Cells Are Sensitive to the Inhibition of IGF-1 Signaling by a Murine Anti-IGF-1R Monoclonal Antibody, mAVE1642

Insulin-like growth factor 1 (IGF-1) is a well-known growth factor for myeloma cells. Thus, therapeutic strategies targeting IGF-1R have been proposed for multiple myeloma treatment. In this study, we investigated the effect of the antagonistic anti-IGF-1R murineAVE1642 Ab (mAVE1642). We show that mAVE1642 selectively inhibits IGF-1R but not insulin signaling in human myeloma cell lines. Since we have previously shown the functional relevance of CD45 expression in the growth of myeloma cells and the association of CD45-negative (CD45neg) status with a less favorable clinical outcome, both CD45-positive (CD45pos) and CD45neg myeloma cell lines were selected for our study. We found that mAVE1642 strongly inhibits the growth of CD45neg myeloma cell lines, leading to a G1 growth arrest, whereas it has almost no effect on the growth of CD45pos myeloma cell lines. Furthermore, mAVE1642 binding induced a significant reduction of IGF-1R expression. We next demonstrated that the overexpression of IGF-1R in the CD45pos myeloma cell line increased Akt phosphorylation but was not sufficient to sensitize these cells to mAVE1642. In contrast, we generated a stable CD45-silencing XG-1 cell line and showed that it became sensitive to mAVE1642. Thus, for the first time, we provided direct evidence that the expression of CD45 renders cells resistant to mAVE1642. Taken together, these results support that therapy directed against IGF-1R can be beneficial in treating CD45neg patients.

The magnitude of Akt/phosphatidylinositol 3'-kinase proliferating signaling is related to CD45 expression in human myeloma cells

In multiple myeloma, the Akt/PI3K pathway is involved in the proliferation of myeloma cells. In the current study, we have investigated the impact of the CD45 phosphatase in the control of Akt/PI3K activation. We show that Akt activation in response to insulin-like growth factor-1 (IGF-1) is highly variable from one human myeloma cell line to another one. Actually, Akt activation is highly related to whether CD45 is expressed or not. Indeed, both the magnitude and the duration of Akt phosphorylation in response to IGF-1 are more important in CD45- than in CD45+ myeloma cell lines. We next demonstrate a physical association between CD45 and IGF-1 receptor (IGF-1R) suggesting that CD45 could be involved in the dephosphorylation of the IGF-1R. Furthermore, the growth of CD45- myeloma cell lines is mainly or even totally controlled by the PI3K pathway whereas that of CD45+ myeloma cell lines is modestly controlled by it. Indeed, wortmannin, a specific PI3K inhibitor, induced a dramatic growth inhibition in the CD45- myeloma cell lines characterized by a G1 growth arrest, whereas it has almost no effect on CD45+ myeloma cell lines. Altogether, these results suggest that CD45 negatively regulates IGF-1-dependent activation of PI3K. Thus, strategies that block IGF-1R signaling and consequently the Akt/PI3K pathway could be a priority in the treatment of patients with multiple myeloma, especially those lacking CD45 expression that have a very poor clinical outcome.

Light-chain only multiple myeloma is due to the absence of functional (productive) rearrangement of the IgH gene at the DNA level

Although most multiple myeloma (MM) cases are characterized by the detection of a monoclonal immunoglobulin in the serum, about 15% of the patients present only immunoglobulin light chains, detected either in the urine or serum or both. These patients are designated as having light-chain (LC) MM. Using fiber-fluorescent in situ hybridization, and in contrast to patients and myeloma cell lines secreting heavy chains (who presented a legitimate functional IgH rearrangement in every case), LC MM never displayed a functional IgH recombination. Interestingly, most LC MM cases presented one IgH allele with a germline configuration (including the DJ region), the second allele being usually involved in an illegitimate recombination. Of note, most of these translocations occurred close to (or at) switch regions, even though in some cases, breakpoints involving nonswitch regions were observed. Thus, this study clearly showed that LC MM is due to the absence of legitimate IgH rearrangement at the DNA level, reflecting possible abnormalities in the IgH gene recombinations during B-cell maturation. Furthermore, it showed that this defect did not prevent the activation of the switch process because most of 14q32 translocations observed in LC MM occurred at switch regions.

Hepatoprotective effect of endogenous nitric oxide during ischemia-reperfusion in the rat

The aim of this study was to evaluate the protective or deleterious effects of endogenous nitric oxide (NO) on liver cells during hepatic ischemia-reperfusion (IR) in the rat. Injury to hepatocytes and endothelial cells was evaluated by determining cytolysis-marker activity in plasma (alanine transaminase [ALT]; aspartate transaminase [AST]) and plasma hyaluronic acid (HA) concentration. Clamping the hepatic pedicle for 45 minutes caused a significant increase in plasma AST and ALT activity after 30 minutes of reperfusion, which reached a maximum (+270% and +740%, respectively) after 6 hours of reperfusion. Plasma HA concentration was significantly higher (+130%) only after 6 hours of reperfusion. Administration of a nonselective NO synthase (NOS) inhibitor, Nomega-nitro-L-arginine (L-NNA; 10 mg/kg iv), 30 minutes before IR, caused marked aggravation of postischemic liver injury, as shown by plasma ALT and AST activity and HA concentration. This deleterious effect was partially prevented by the simultaneous injection of L-arginine, the endogenous NO precursor (100 mg/kg iv). Interestingly, L-arginine alone limited postischemic damage (AST, -25%; ALT, -45%; HA, -21% vs. untreated IR rats at 6 hours reperfusion). Pretreatment with the Guanosine 3':5'-cyclic monophosphate-independent vasodilator, prazosin, partially reversed L-NNA effects, but it did not protect untreated IR animals. Pretreatment with aminoguanidine, a selective inhibitor of inducible NOS, did not aggravate hepatic IR injury. Thus, endogenous NO, probably produced by an early and transient activation of a constitutive NOS, protects both hepatocytes and endothelial cells against liver ischemia-reperfusion injury, and this effect is not entirely a result of vasorelaxation.

Increased expression of liver PKC alpha in hypoinsulinemic diabetic rats: a post-translational effect

Ca2+-dependent protein kinase C (cPKC) activity and expression have been studied in livers from hypoinsulinemic streptozotocin (STZ)-induced diabetic and untreated control rats. In diabetic rats, cPKC activity was slightly decreased in liver total particulate and nuclear fractions but was unchanged in mitochondrial-lysosomal, microsomal and cytosolic fractions. On Western immunoblot analysis, PKC alpha was identified as two distinct proteins of 90 and 81 kDa. In diabetic rats, the abundance of the 90 kDa protein was increased in most subcellular fractions with a maximum in the cytosolic and microsomal fractions (180%) but that of the 81 kDa protein was unchanged. PKC beta2 was detected as a single 81 kDa protein in cytosolic and microsomal fractions with unchanged levels in diabetic rats. Liver PKC alpha mRNA levels as measured by reverse transcription and competitive PCR amplification were similar in diabetic and control rats. The increased expression of PKC alpha protein in diabetic rats was reversed by insulin but not by phlorizin, suggesting that it did not result from hyperglycemia. We conclude that STZ-induced diabetes induces the expression of a biologically inactive form of PKC alpha which differs from active PKC alpha by an undefined post-translational modification, possibly an increase in phosphorylation state.

Use of a renal tubule cell line (LLC-PK1) to study the nephrotoxic potential of a kappa-type Bence-Jones protein

The cytotoxicity of a Bence-Jones protein was assessed using a porcine renal tubule cell line (LLC-PK1), with the aim of developing a model for studying the potential nephrotoxicity of these proteins. The effects of a kappa Bence-Jones protein on cell viability were studied by means of biochemical methods (supravital dye uptake and measurement of cellular enzyme activities) and morphological electron microscopy. After a 24-h-treatment with Bence-Jones protein, a moderate cytotoxicity (about 15%) was noted but only a minor difference compared to treatment with bovine albumin in the same conditions. The morphological study showed a few cells in the process of lysis, but their numbers were insufficient for the demonstration of a clear cytotoxic effect. Immunocytochemical studies showed Bence-Jones protein fixation on some cells, especially on the outer membrane. Labeling of the hyaloplasm and basal pole of a few cells pointed to internalization of protein by LLC-PK1 cells. Although the cytotoxicity of the Bence-Jones protein tested here was only moderate, the use of this model enabled its cytotoxic effect to be distinguished from that of beta-lactoglobulin. This isolate could serve as a "moderate control" for a later study with a BJP having caused acute renal failure.