Bintrafusp alfa induced multiple self-healing cutaneous keratoacanthoma-like squamous proliferations

We present a case where bintrafusp alfa induced self-resolving keratoacanthomas and squamous cell carcinoma (SCC)-like cutaneous proliferations in a patient. With the development and use of novel targeted therapies, it is important to be aware of possible cutaneous adverse events. It is also prudent to emphasize that in many cases the development of lesions such as SCC-like cutaneous proliferations is reversible, which should be considered when counselling patients on whether to stop treatment.

Dilute Intralesional 5-Fluorouracil for the Treatment of Squamous Cell Carcinomas and Keratoacanthomas: A Case Series

BACKGROUND

Intralesional 5-fluorouracil (5-FU) is a promising, yet sparsely studied alternative to surgical treatment for nonmelanoma skin cancer (NMSC).1 Previous studies of intralesional 5-FU have reported concentrations ranging from 30 to 50 mg/mL. To the best of our knowledge, this case series represents the first reported use of intralesional 5-FU 10.0 mg/mL and 16.7 mg/mL for NMSC.

METHODS

A retrospective chart review identified 11 patients who received intralesional 5-FU 10.0 mg/mL and 16.7 mg/mL for 40 cutaneous squamous cell carcinomas and 10 keratoacanthomas. We describe the characteristics of these patients and calculate the clinical clearance rate of dilute intralesional 5-FU therapy for NMSC at our institution.

RESULTS

Dilute intralesional 5-FU successfully treated 96% (48/50) of the study lesions, providing complete clinical clearance in 82% (9/11) of patients across a mean follow-up time of 21.7 months. All patients tolerated their treatments well with no reported adverse effects or local recurrences.

DISCUSSION

The use of more dilute preparations of intralesional 5-FU for NMSC may be a means of reducing cumulative dose and dose-dependent adverse reactions while maintaining clinical clearance. J Drugs Dermatol. 2023;22(5): doi:10.36849/JDD.5058.

A case of new-onset vitiligo in a patient on tofacitinib and brief review of paradoxical presentations with other novel targeted therapies

With recent advancements in the understanding of vitiligo pathogenesis, Janus kinase (JAK) inhibitors have emerged as a promising new treatment modality, but their effects remain incompletely elucidated. Tofacitinib, an oral JAK 1/3 inhibitor approved for the treatment of rheumatoid arthritis, has previously been shown to induce significant re-pigmentation in vitiligo. However, as with other novel targeted therapies, cutaneous adverse effects have been observed. We report a 36-year-old woman with a history of rheumatoid arthritis, refractory to multiple pharmacotherapies, who was initiated on tofacitinib and subsequently developed progressive depigmented patches consistent with new-onset vitiligo. Although definitive causation cannot be established in this case without additional studies, it is important to note that many targeted therapies have the potential to induce paradoxical effects, that is, the occurrence or exacerbation of pathologic conditions that have been shown to respond to these medications. Paradoxical findings with other targeted therapies include the occurrence of melanoma during treatment with BRAF inhibitors, keratoacanthomas with PD-1 inhibitors, vitiligo and psoriasis with TNF-alpha inhibitors, and hidradenitis suppurativa with various biologic agents. Although JAK inhibitors hold therapeutic promise in the treatment of inflammatory skin disorders, further research is warranted to more fully comprehend their effects.

Dermatological approach to vemurafenib skin toxicity: a single centre experience

BACKGROUND

Targeted therapies have recently changed the approach to advanced melanoma. RAF inhibitors represent the emerging standard of care for metastatic BRAF mutated melanomas. Cutaneous reactions are the most common side effects during vemurafenib treatment, and affect the quality of life. The aim of this study was to provide some practical advices to manage the drug related cutaneous reactions.

METHODS

A cohort of BRAF-mutated metastatic melanoma patients treated at our institution included 20 female and 21 male patients; median age was 56 years (32-87 years). All patients were treated at a dose of 960 mg b.i.d. orally.

RESULTS

After a median treatment duration of 7 months (range 0.5-25.2), 29/39 patients (74.4%) developed cutaneous toxicities. We identified 22 cases of maculo-papular rash (56%) and 18 of warts (46%); in a total of 10 cases we observed alterations of keratinization (25.6%), while 6 of our patients presented photosensitivity (15 %). Six patients developed keratoacanthomas; no second melanomas were observed.

CONCLUSIONS

Skin involvement during vemurafenib treatment is frequent but in the majority of cases cutaneous side effects are self-limiting and easy to manage. Moreover, sun protection is mandatory in vemurafenib treated patients, and should be started together with BRAF inhibitor in order to minimize the impact of photosensitivity on quality of life.

Cutaneous Epithelial Lesions Induced by N-Methyl-N-nitrosourea in Male Sprague-Dawley Rats: A Possible Animal Model for Human Keratoacanthoma

A single intraperitoneal injection of 50 or 75 mg/kg N-methyl-N-nitrosourea in male Sprague-Dawley rats at 4 weeks of age, dose-dependently resulted in cutaneous epithelial cysts and tumors of pilosebaceous origin. Cysts were composed of epidermal cysts or mixed epidermal and inner root sheath hybrid cysts. The majority of induced tumors were keratoacanthomas. A few tumors were trichofolliculomas, trichoblastomas, pilomatricomas, or sebaceous adenomas. All tumors were benign pilosebaceous tumors. Keratoacanthomas were crater-shaped tumors with thick infoldings of epithelium containing keratohyalin granules (epidermal lip) that abruptly changed to epithelium containing trichohyalin granules. The morphological similarity and resemblance of keratin 1, 10, and 14 profiles, and p63 and β-catenin expression between mixed epidermal and inner root sheath hybrid cysts and keratoacanthomas suggests that hybrid cysts progressed to keratoacanthomas, and the cells from infundibular cells to inner root sheath cells of the pilar segment seem to be the origin of rat keratoacanthomas. Immunohistochemical localization of keratins 1, 10 and 14, p63, and β-catenin in trichofolliculoma, trichoblastoma, and pilomatricoma, as well as keratoacanthoma, may indicate tumor histogenesis.

Cutaneous adverse events during vemurafenib therapy

BACKGROUND

Vemurafenib, an oral agent that selectively targets the BRAF V600E mutation, has recently emerged as the mainstay of treatment in patients with BRAF-positive stage IV melanoma. A spectrum of cutaneous adverse events has been associated with vemurafenib, ranging from benign rashes to malignant side effects such as keratoacanthoma and squamous cell carcinoma.

OBJECTIVE

In this article, we review clinical data regarding the frequency and severity of the common dermatologic side effects associated with vemurafenib; case series and noncontrolled studies evaluating the safety of vemurafenib therapy are used to further characterize these adverse events.

CONCLUSION

Benign vemurafenib-induced side effects generally tend not to be severe or life threatening, with most patients managed by dose interruptions, dose reductions, or topical therapies. Squamous cell carcinomas and keratoacanthomas associated with vemurafenib therapy are easily treated by simple excision of the lesion without discontinuation of vemurafenib. Thus, awareness of potential adverse events coupled with routine dermatologic assessment and timely management will allow for optimal therapeutic benefit in patients receiving vemurafenib therapy.

[Cellular and molecular mechanisms of carcinogenic side effects and resistance to BRAF inhibitors in metastatic melanoma with BRAFV600 mutation: state of the knowledge]

Cutaneous melanoma is a malignant tumor with a high metastatic potential. If an early treatment is associated with a favorable outcome, the prognosis of metastatic melanoma remains poor. Advances in molecular characterization of cancers, notably the discovery of BRAF gene mutations in metastatic melanoma, allowed to the recent development of targeted therapies against mutated BRAF protein. Despite high tumor response rates observed in clinical trials, these new drugs are associated with frequent secondary tumor resistance occurrence and paradoxical carcinogenic side effects. The cellular and molecular mechanisms of these carcinogenic side effects and secondary resistance are not yet fully elucidated and are actually intensely studied. This review of the literature focus on the mechanisms of these carcinogenic side effects and on the tumor resistance associated with anti-BRAF targeted therapies.

A role for NF-κB activity in skin hyperplasia and the development of keratoacanthomata in mice

BACKGROUND

Previous studies have implicated NF-κB signaling in both cutaneous development and oncogenesis. However, these studies have been limited in part by the lethality that results from extreme over- or under-expression of NF-κB in available mouse models. Even cre-driven tissue specific expression of transgenes, or targeted deletion of NF-κB can cause cell death. Therefore, the present study was undertaken to evaluate a novel mouse model of enhanced NF-κB activity in the skin.

METHODS

A knock-in homologous recombination technique was utilized to develop a mouse model (referred to as PD mice) with increased NF-κB activity.

RESULTS

The data show that increased NF-κB activity leads to hyperproliferation and dysplasia of the mouse epidermis. Chemical carcinogenesis in the context of enhanced NF-κB activity promotes the development of keratoacanthomata.

CONCLUSION

Our findings support an important role for NF-κB in keratinocyte dysplasia. We have found that enhanced NF-κB activity renders keratinocytes susceptible to hyperproliferation and keratoacanthoma (KA) development but is not sufficient for transformation and SCC development. We therefore propose that NF-κB activation in the absence of additional oncogenic events can promote TNF-dependent, actinic keratosis-like dysplasia and TNF-independent, KAs upon chemical carcinogensis. These studies suggest that resolution of KA cannot occur when NF-κB activation is constitutively enforced.

Multiple eruptive keratoacanthomas associated with leflunomide

A 78-year-old woman diagnosed with rheumatoid arthritis without a history of skin tumors or immunosuppressive medication, started treatment with leflunomide. One month after the introduction of the drug, and for two consecutive years, she developed multiple crateriform nodules and papules on her lower extremities . Biopsy specimens showed keratoacanthomas and squamous-cell carcinomas. Owing to suspicion that the drug could be implicated in the appearance of these tumors, the patient decided to suspend the drug. No new skin lesions have appeared in seventeen months of clinical follow-up. There have been several published case reports of multiple keratoacanthomas associated with immunosuppressive therapy such as sorafenib and imiquimod. However, we found no mention in the literature of the eruption of multiple keratoacanthomas in patients with rheumatoid arthritis treated with leflunomide. We suggest, that the the sudden appearance of skin tumors in our patient is related to the introduction of leflunomide, but additional case reports are required to confirm this association.

[Vemurafenib (Zelboraf) in the therapy of melanoma]

The incidence of malignant melanoma is continuously rising, but the therapy of advanced melanoma remains insufficient. Advances in the understanding of the immunological and genetical background resulted in the development of a new target therapeutic agent, vemurafenib (Zelboraf) accepted by the FDA in 2011 and by the EMA in 2012. Vemurafenib improved the overall and progression-free survival of untreated melanoma with the mutation BRAF V600E. In a phase III study vemurafenib was associated with a 63% reduction in the risk of deaths compared with dacarbazine and of 74% in the risk of either death or disease progression. Objective response was 48% in the vemurafenib and 5% in the dacarbazine arm. Vemurafenib has special side effects, surprisingly even secondary skin tumors. Additional research is needed to understand the mechanism of drug resistance and to find new targeted therapeutic agents and combinations.

Cutaneous effects of BRAF inhibitor therapy: a case series

BACKGROUND

The cutaneous effects of rapidly accelerated fibrosarcoma kinase B (BRAF) inhibitors are not well understood. Squamous cell carcinoma (SCC), keratoacanthoma, and photosensitivity have been described in patients taking BRAF inhibitors.

PATIENTS AND METHODS

To characterize the timing and frequency of skin lesions in patients receiving BRAF inhibitor therapy, we utilized a retrospective case review of 53 patients undergoing treatment with BRAF inhibitors for 4-92 weeks of therapy. Patients were evaluated at baseline, and then followed at 4- to 12-week intervals. Charts were retrospectively reviewed, and the morphology and timing of cutaneous events were recorded.

RESULTS

Thirty-three of the 53 charts met exclusion/inclusion criteria, 15 were treated with vemurafenib, and 18 were treated with GSK 2118436/GSK 1120212. Of 33 patients treated with BRAF inhibitor, 13 developed photosensitivity (39.4%), 10 developed actinic keratoses (30.3%), 10 developed warts (30.3%), and 6 developed SCC (18.2%).

CONCLUSIONS

Multiple cutaneous findings were observed in the 33 patients taking BRAF inhibitors. The previously described association with SCC and photosensitivity was observed in these patients as well. Over half of the observed SCCs were invasive in nature. Photosensitivity continues to be frequent with BRAF inhibitors. Patients taking BRAF inhibitors should have regular full body skin exams. Further studies are necessary to better elucidate the rates of these adverse cutaneous effects.

Oral carcinogenicity study with nickel sulfate hexahydrate in Fischer 344 rats

Until now, existing data on the oral carcinogenicity of nickel substances have been inconclusive. Yet, the assessment of oral carcinogenicity of nickel has serious scientific and regulatory implications. In the present study, nickel sulfate hexahydrate was administered daily to Fischer 344 rats by oral gavage for 2 years (104 weeks) at exposure levels of 10, 30 and 50 mg NiSO(4).6H(2)O/kg. This treatment produced a statistically significant reduction in body weight of male and female rats, compared to controls, in an exposure-related fashion at 30 and 50 mg/kg/day. An exposure-dependent increase in mortality was observed in female rats. However, the overall study survival rate (males and females) was at least 25 animals per group (compliant with OECD guidelines) in the treated animals. Daily oral administration of nickel sulfate hexahydrate did not produce an exposure-related increase in any common tumor type or an increase in any rare tumors. One tumor type was statistically increased in a nickel sulfate-treated group compared to the study controls (keratoacanthoma in the 10 mg NiSO(4).6H(2)O/kg/day males), but there was no exposure-response relationship for this common tumor type. This study achieved sufficient toxicity to reach the Maximum Tolerated Dose (MTD) while maintaining a sufficiently high survival rate to allow evaluation for carcinogenicity. The present study indicated that nickel sulfate hexahydrate does not have the potential to cause carcinogenicity by the oral route of exposure in the Fischer 344 rat. Data from this and other studies demonstrate that inhalation is the only route of exposure that might cause concern for cancer in association with nickel exposures.

Development of a keratoacanthoma after topical photodynamic therapy with 5-aminolevulinic acid

Since its FDA approval in 1999, photodynamic therapy (PDT) with topical 5-aminolevulinic acid has become an increasingly popular modality for the treatment of actinic keratosis (AKs). It is hoped that in addition to improving clinical signs and symptoms of AKs, PDT might prevent the development of skin cancer. We present a case of a patient developing a keratoacanthoma immediately following PDT for AKs.

Prostaglandin E receptor EP3 deficiency modifies tumor outcome in mouse two-stage skin carcinogenesis

We have recently shown that the prostaglandin E(2) (PGE(2)) receptor EP(3) plays an important role in suppression of colon cancer cell proliferation and that its deficiency enhances late stage colon carcinogenesis. Here we examined the effects of EP(3)-deficiency on two-stage skin carcinogenesis. 7,12-Dimethylbenz[a]anthracene (50 microg/200 microl of acetone) was thus applied to the back skin of female EP(3)-knockout and wild-type mice at 8 weeks of age, followed by treatment with 12-O-tetradecanoylphorbol-13-acetate (5 microg/200 microl of acetone) twice a week for 25 weeks. First tumor appearance was observed in EP(3)-knockout mice at week 10, which was 3 weeks later than in EP(3) wild-type mice, and multiplicity observed at week 11 was significantly lower in the EP(3)-knockout case. However, histological examination showed that the tumor incidence and multiplicity at week 25 were not significantly changed in knockout mice and wild-type mice (incidence, 19/19 versus 23/24; multiplicity, 3.58 +/- 0.51 versus 3.17 +/- 0.63, respectively). Interestingly, there were no squamous cell carcinomas (SCCs) in the EP(3)-knockout mice, while SCCs were observed in 3 out of 24 wild-type mice. Furthermore, benign keratoacanthomas only developed in EP(3)-knockout mice (6/19 versus 0/24, P < 0.01). The results suggest that PGE(2) receptor EP(3) signaling might contribute to development of SCCs in the skin.

Early and explosive development of nodular basal cell carcinoma and multiple keratoacanthomas in psoriasis patients treated with cyclosporine

The use of cyclosporine to treat psoriasis has been widely adopted since 1997, when the microemulsion form (Neoral) became available. While the causal relationship between cyclosporine and the development of malignant neoplasms has been well described in the transplant literature, it is difficult to apply this relationship to cyclosporine-treated psoriasis, since lower dosages are used (3-5 mg/kg/d vs. 7-15mg/kg/d) for a shorter duration. Current literature suggests that cancer risk is not increased when cyclosporine is used in dermatologic doses for less than 2 years in healthy patients who are not on other immunosuppressants. We report two patients with explosive basal cell carcinoma and keratoacanthoma development, respectively, within 3 months of initiation of cyclosporine. Neither patient had a history of skin cancer, had received PUVA therapy, or was on additional immunosuppressive therapy. To our knowledge, there have been no previous reports of the development of similar lesions in cyclosporine-treated psoriatic patients within such a short timeframe. The results of these patients may herald the need for increased awareness by dermatologists for explosively-growing neoplasms in the setting of cyclosporine-treated psoriasis.

An assessment of the carcinogenic potential of shea oleine in the rat

Shea oleine, an oil fraction derived from the nut of the tree Butyrospermum parkii, is used as a frying oil. As part of a series of studies, this investigation examined the carcinogenic potential of 15% (w/w) shea oleine in comparison with 15% (w/w) sheanut oil, and palm oil following dietary administration to rats over 104 weeks. The assessment comprised an evaluation of mortality, clinical signs, body weight, food intake, clinical pathology, organ weights and macroscopic and histopathological examination plus tumour type and incidence evaluation. Results showed that shea oleine produced no adverse effects and no evidence of tumorigenic potential compared to other commercially available sheanut and palm oils in the rat. Notable differences were confined to reduced body weight gain and food intake, reduced cholesterol and increased alkaline phosphatase levels, reduced heart weight and an increased incidence of pulmonary lipidosis with shea oleine diets. The latter effect may reflect a naturally lower incidence of this finding with palm oil diets. Tumour findings, specific to shea oleine diets, were restricted to an increase in the number of hepatomas for females, pancreatic exocrine adenomas for males and skin keratoacanthomas for males fed shea oleine diets. The increase in the incidence of hepatomas with treatment was thought to be related to the high fat content of the diets. The incidence of these tumour findings was similar to that given in published data for the Wistar rat, or the 'in house' values for tumour incidence in rats fed high-fat diets. In conclusion, none of the findings in this study were considered to be adverse effects. In comparison with other commercially available edible oils, shea oleine showed no tumorigenic potential following dietary administration at 7.5 g/kg/day in the rat.

Benzo[a]pyrene carcinogenicity is lost in mice lacking the aryl hydrocarbon receptor

The contribution of the aryl hydrocarbon receptor (AhR) in induction of a battery of xenobiotic-metabolizing enzymes has been studied extensively. However, no direct proof has been obtained that it plays a role in modulating carcinogenesis. To address the question of whether AhR is required for tumor induction, we have investigated the response of AhR-deficient mice to benzo[a]pyrene (B[a]P), a widely distributed environmental carcinogen. B[a]P treatment induced expression of the cytochrome P450 gene Cyp1a1 in the skin and liver of AhR-positive mice bearing +/+ and +/- genotypes and did not induce expression of the cytochrome P450 gene Cyp1a1 in AhR-null mice in either skin or liver. In contrast, Cyp1a2 gene expression was positive in liver irrespective of the presence or absence of the AhR gene, or B[a]P treatment, although its inducibility was lost in the AhR(-/-) mouse. All AhR-positive male mice of both +/+ and +/- genotypes that received subcutaneous injection of B[a]P (2 mg) on the first and the eighth days had developed subcutaneous tumors at the site of injection at the end of the 18-week experiment. In contrast, no tumors were apparent in any of the AhR-deficient mice. Likewise, topical application of B[a]P (200 microg) at weekly intervals to the skin of female mice for 25 weeks produced skin tumors only in the AhR-positive mice. Thus the carcinogenic action of B[a]P may be determined primarily by AhR, a transcriptional regulator of the gene for CYP1A1. The results of the present study provide direct evidence that AhR is involved in carcinogenesis.

Dose-dependent mutation profile in the c-Ha-ras proto-oncogene of skin tumors in mice initiated with benzo[a]pyrene

Female CD-1 mice were treated topically with a low (25-50 nmol) or high (800 nmol) dose of benzo[a]pyrene (BP) or acetone vehicle, followed by 5 nmol 12-O-tetradecanoylphorbol 13-acetate (TPA) twice a week for 26 weeks. Selective UV radiation fractionation followed by PCR methods were used to analyze histologically defined subsets of cells (approximately 100-200 cells) on formalin-fixed, paraffin-embedded and H&E stained microscope sections. DNA samples from normal-appearing, hyperplastic or tumor regions from the skin of animals from each treatment group were isolated and amplified by PCR with c-Ha-ras-specific primers. Single-strand conformation polymorphism (SSCP) analyses were performed on both exon 1 and 2 products from each sample. DNA extracted from each aberrant band of SSCP analyses was amplified by PCR for further sequence analysis. The data indicate that c-Ha-ras mutations can be detected in normal-looking and hyperplastic epidermal cells as well as in tumor cells obtained from mice initiated with BP and promoted with TPA. The frequencies of c-Ha-ras mutations for normal-looking, hyperplastic and tumor samples were 3/20 (15%), 8/17 (47%) and 58/68 (85%), respectively, for the low dose group and 8/18 (44%), 10/20 (50%) and 64/86 (74%), respectively, for the high dose group. These observations indicate that there were no dose dependencies in the mutation frequencies for normal-looking, hyperplastic and tumor samples. For combined high dose and low dose samples, differences in mutation frequencies of the c-Ha-ras gene between the normal-looking, hyperplastic and tumor samples were highly significant (P < 0.0001, Fisher's exact test). All mutations detected were located at codons 12, 13 and 61 of the c-Ha-ras gene. With the numbers in parentheses indicating the nucleotide position in the coding sequence of the c-Ha-ras proto-oncogene, the distributions of mutations for G-->A (35), G-->T (35), G-->C (37), G-->T (38), C-->A (181), A-->T (182) and A-->G (182) in the low dose tumors were 5, 2, 11, 74, 0, 7 and 2%, respectively, and the distribution of mutations in tumors from animals treated with a high dose of BP were 3, 7, 13, 61, 15, 1 and 0%, respectively. Differences in the global mutation spectra (site and kind of all mutations) for the c-Ha-ras gene between the high and low dose group tumors were statistically significant (P < 0.004, Fisher's exact test) and the major difference between these two groups was C-->A (181) base substitutions. In summary, our data indicate that: (i) 79% of the BP/TPA skin tumors in CD-1 mice had c-Ha-ras mutations for the combined data for high dose and low dose tumors; (ii) the major mutations detected in BP/TPA skin tumors were G-->T transversions; (iii) the global mutation profile in the c-Ha-ras proto-oncogene in skin tumors obtained after initiation with a low dose of BP was different from that obtained after initiation with a high dose of BP.

Occupationally related tumors in tar refinery workers

BACKGROUND

The study comprised 606 workers with tar-induced dermatosis employed in a German tar refinery. During the period from 1946 to 1996 they were recognized as having an occupational disease.

OBJECTIVE

The aim of this study was to characterize the histologic findings and the localization of the occupational dermatosis and to determine the latency period of the carcinomas from the beginning of exposure in the tar refinery to the first occurrence of malignant skin tumors. Furthermore, the study aimed to check whether other skin changes were frequently diagnosed in addition to known tar-induced tumors.

METHODS

The data were collected retrospectively from the documents of the Employer's Liability Insurance Association.

RESULTS

Surgical removal of 4754 skin tumors was documented up to the end of 1996 in the study. In 90% of cases the histologic diagnosis was confirmed. Among other conditions, this yielded 2490 precancerous stages, 380 squamous cell carcinomas, 218 basal cell carcinomas, and 182 keratoacanthomas. The skin tumors were found mainly in the facial area, as well as on the forearms and hands. Latency from the first exposure in the tar refinery until manifestation of tar-induced dermatosis covered a period of 57 years.

CONCLUSION

In comparison to the general population, the ratio of squamous cell to basal cell carcinomas was shifted toward the squamous cell carcinomas (1.7:1). Sunlight is known to be a cofactor in the pathogenesis of keratosis, squamous cell carcinomas, and basal cell carcinomas. However, the difference in location of these tumors shows that the role sunlight plays in the pathogenesis of precancerous lesions and squamous cell carcinomas may be overvalued. The latency period from the beginning of exposure to the manifestation of squamous cell carcinomas could not be evaluated because of an intervention bias as a result of preventive excisions of precancerous lesions. The frequent occurrence of keratoacanthomas (in 18.7% of the workers) and the early age at which this disease became manifest relative to the general population (median, 55 years) indicate that employment in a tar refinery can primarily or secondarily cause keratoacanthomas.

Co-operation between follicular ornithine decarboxylase and v-Ha-ras induces spontaneous papillomas and malignant conversion in transgenic skin

Ornithine decarboxylase (ODC) is aberrantly regulated in tumor cells and results in high basal levels of ODC and polyamines in many epithelial tumors. To determine if elevated ODC/polyamine levels can co-operate with a mutant Ha-ras gene in mouse skin tumorigenesis, double transgenic mice were generated by breeding K6/ODC transgenic mice with TG.AC v-Ha-ras transgenic mice. A K6 keratin promoter drives the ODC transgene in K6/ ODC transgenic mice, which results in elevated ODC/ polyamine levels directed to the outer root sheath cells of hair follicles. TG.AC transgenic mice carry a v-Ha-ras transgene while still retaining two normal c-Ha-ras alleles. Transgenic mice that possess only the K6/ODC or the v-Ha-ras transgene did not develop tumors unless treated with either a carcinogen or a tumor promoter, respectively. However, a high percentage of double transgenic mice possessing both the K6/ODC and v-Ha-ras transgenes developed spontaneous tumors. All tumors were well-differentiated keratoacanthomas, some of which progressed to carcinomas within 2 months. The development and the maintenance of these ODC/ras tumors was ODC-dependent since alpha-difluoromethylornithine (DFMO), a specific ODC inhibitor, prevented the formation and caused the regression of these tumors. These findings indicate that ODC overexpression and an activated Ha-ras are sufficient to produce a high rate of malignant transformation in an animal model. The ODC/ras double transgenic mouse provides a simple in vivo model without the use of chemical carcinogens or tumor promoters in which to test downstream effectors that play a key role in mediating the development of epithelial tumors resulting from the cooperation between ODC and v-Ha-ras.

Human papillomavirus and widespread cutaneous carcinoma after PUVA photochemotherapy

BACKGROUND

Oral psoralen with UV-A (PUVA) photochemotherapy is known to cause cutaneous malignancies and has been associated with cutaneous immunosuppression. Human papillomavirus infection has also been associated with cutaneous malignancies and with immunosuppressed individuals. We therefore sought evidence of human papillomavirus infection in a patient with a long history of PUVA therapy and multiple cutaneous malignancies.

OBSERVATIONS

During a 15-year period, an otherwise healthy patient with psoriasis who had undergone a 10-year course of PUVA photochemotherapy developed 13 squamous cell carcinomas, eight lesions diagnosed as "squamous cell carcinoma vs keratoacanthoma," 14 other keratoacanthomas, six basal cell carcinomas, one melanoma in situ, and 18 other keratinocytic dysplasias. Twenty-two of the 30 lesions tested for human papillomavirus DNA by polymerase chain reaction were positive for type 16/18, including six of the seven basal or squamous cell carcinomas tested.

CONCLUSION

We hypothesize that PUVA therapy-induced immunosuppression may play an important role in PUVA-related carcinogenesis by affecting the extent and pathogenicity of human papillomavirus infection.

Differential expression of the H-ras mutated and normal alleles in rabbit DMBA-induced keratoacanthomas

Keratoacanthomas (KAs) are benign and self-regressing tumors in which a high incidence of the mutated H-ras oncogene has been observed both in humans and in experimental models. To determine the level of expression of the mutated H-ras allele with respect to its normal counterpart in 7,12-dimethylbenz(a)anthracene (DMBA)-induced KAs in rabbit skin, we have utilized a quantitative technique based on reverse transcription polymerase chain reaction (RT-PCR) and selective cleavage of the mutated molecules of the H-ras gene. Analysis of 16 KAs showed that the mutated H-ras transcripts were up to 3-fold more abundant than the non-mutated H-ras transcript in the different tumors. This higher expression of the mutated allele appears to correlate with increased differentiation in the KAs and in turn may contribute to tumor regression.

Inhibition of benzoyl peroxide-induced tumor promotion and progression by copper(II)(3,5-diisopropylsalicylate)2

The ability of a biomimetic superoxide dismutase agent, copper(II)(3,5-diisopropylsalicylate)2 (CuDIPS), to modulate benzoyl peroxide (BzPo)-induced tumor promotion and progression in mouse skin multistage carcinogenesis was evaluated. The results showed a significant inhibition of tumor incidence by CuDIPS pretreatment during promotion-progression. Different types of tumors were developed: papillomas, keratoacanthomas and squamous cell carcinomas. There was a significant increase in the keratoacanthoma-papilloma ratio when the period of treatment with BzPo was prolonged, which was inhibited by CuDIPS pretreatment. CuDIPS induced a significant inhibition of malignant conversion. Our results suggest that reactive oxygen species could be important in BzPo-induced promotion and progression.

ras activation in human tumors and in animal model systems

Environmental agents such as radiation and chemicals are known to cause genetic damage. Alterations in a limited set of cellular genes called proto-oncogenes lead to unregulated proliferation and differentiation. We have studied the role of the ras gene family in carcinogenesis using two different animal models. In one case, thymic lymphomas were induced in mice by either gamma or neutron radiation, and in the other, keratoacanthomas were induced in rabbit skin with dimethylbezanthracene. Human keratoacanthomas similar to the ones induced in rabbits were also analyzed. We found that different types of radiation such as gamma rays and neutrons, induced different point mutations in ras genes. A novel K-ras mutation in codon 146 has been found in thymic lymphomas induced by neutrons. Keratoacanthomas induced in rabbit skin by dimethylbenzanthracene show a high frequency of H-ras-activated genes carrying a mutation in codon 61. The same is observed in human keratoacanthomas, although mutations are in both the 12th and the 61st codons of the H-ras gene. H-ras activation is less frequent in human squamous cell carcinomas than in keratoacanthomas, suggesting that ras genes could play a role in vivo in differentiation as well as in proliferation.

Oncogene involvement in tumor regression: H-ras activation in the rabbit keratoacanthoma model

Activated H-ras genes are present in a number of skin tumors induced in animals by carcinogen treatment. The involvement of the ras oncogenes in tumorigenesis was investigated in keratoacanthomas, benign and self-regressing tumors, as well as malignant squamous cell carcinomas. Both tumors were induced in rabbit ears by repeated applications of 7,12 dimethylbenz(a)anthracene (DMBA). The rabbit H-ras gene was cloned and sequenced. PCR analysis revealed that approximately 82% of the keratoacanthoma DNAs contained an A:T to T:A transversion in codon 61. The relative levels of H-ras transcript were increased in keratoacanthomas compared to normal skin and the activated allele was expressed in tumors, even during the regressing phase. Although a G:C to A:T mutation in codon 12 of the H-ras and an activated N-ras gene were found in two squamous cell carcinomas, the frequency of H-ras activation in codon 61 was much lower (40%) in the malignant tumours induced by the same carcinogen treatment. Therefore, DMBA induced at least two types of genetic lesions in this system: H-ras activation, present in most regressing keratoacanthomas, and activation of other unidentified oncogenes which may result in the development of malignant tumors. Our observations indicate that expression of an activated H-ras gene, in this system, is neither sufficient to induce a malignant phenotype nor even capable of maintaining the growth of a benign tumor and suggest that it could be involved in tumor regression.

Carcinogenic property of JBO(P) variety of jute batching oil

The topical application of neat JBO-P variety of jute batching oil (JBO) three times a week has been found to produce skin tumours locally with 13 weeks of treatment on Swiss albino mice. In another set of experiments, 3 times/week topical application of JBO on Swiss albino mouse skin previously initiated (s.c., 1 mg/g body wt.) with urethane resulted in induction of tumours (squamous cell papillomas and keratoacanthomas) in 8 weeks. These results suggest that the JBO-P variety of jute batching oil could be a complete carcinogen or a tumour promoting substance on mouse skin.

H-ras activation in benign and self-regressing skin tumors (keratoacanthomas) in both humans and an animal model system

The involvement of the ras oncogenes in tumorigenesis was investigated in keratoacanthomas, which are benign and self-regressing skin tumors, both in humans and in a corresponding animal model system. Keratoacanthomas were induced on rabbit ears by repeated applications of 7,12-dimethylbenz(a)anthracene. About 60% of the tumor DNAs produced transformed foci after transfection into NIH 3T3 cells, and in all of them the transforming gene was identified as H-ras by Southern and Northern (RNA) hybridization. Immunoprecipitation experiments suggested that the transforming rabbit H-ras protein carried a mutation in codon 61. In addition, an activated H-ras gene was detected in a human keratoacanthoma by using a nude mouse tumorigenesis assay after transfection of tumor DNA into NIH 3T3 cells. This is the first report of ras activation in a benign human tumor. The transforming human H-ras gene showed a point mutation in codon 61 that would result in leucine instead of the glutamine present in the normal gene product. The finding of ras activation in tumors that are not only benign but also self-regressing indicates that activated ras genes are not sufficient to maintain a neoplastic phenotype, although they likely play a role in early stages of tumorigenesis.

Assay of 1-nitropropane, 2-nitropropane, 1-azoxypropane and 2-azoxypropane for carcinogenicity by gavage in Sprague-Dawley rats

1-Nitropropane (1-NP), 2-nitropropane (2-NP), 1-azoxypropane (1-AP) and 2-azoxypropane (2-AP), were assayed for carcinogenicity by gavage in male Sprague-Dawley rats. 2-NP was given at 1 mmol/kg three times per week for 16 weeks. 1-NP (1 mmol/kg), 1-AP (0.1 mmol/kg), 2-AP (0.1 mmol/kg) or Emulphor EL-620 vehicle was given three times per week for 16 weeks, and then once per week for 10 weeks. In the 2-NP treated group both benign and malignant liver tumors occurred in 100% of the animals. No treatment related tumors occurred in rats receiving 1-NP. In rats treated with 1-AP, a high incidence of skin tumors (100%), mostly keratoacanthomas, and of tumors of the nasal cavity (59%) was observed. Rats which were given 2-AP also showed an increased incidence of skin keratoacanthomas (21%), but not of other tumors. These findings (i) confirm, using the oral route of administration, the results of inhalation studies by others indicating the potent hepatocarcinogenicity of 2-NP, (ii) establish a practical model in which the mechanism of 2-NP carcinogenicity can now be more readily studied, and (iii) demonstrate that 1-AP, and probably 2-AP, like other aliphatic azoxy compounds thus far examined, are carcinogenic in rats.

Enhanced malignant progression of mouse skin tumors by the free-radical generator benzoyl peroxide

Chemical carcinogenesis in mouse skin can be divided into the processes of initiation, promotion, and progression. The free-radical generator benzoyl peroxide is moderately active during the promotion stage. Repetitive treatment of mouse benign skin tumors (papillomas) with benzoyl peroxide (20 mg, twice weekly) increased the number of cumulative carcinomas per group by 325% and the number of keratoacanthomas by 44% compared to tumor-bearing Sencar mice treated with the promoter 12-O-tetradecanoylphorbol-13-acetate. The lack of increase in the number of cumulative papillomas per group due to benzoyl peroxide treatment suggests that benzoyl peroxide enhanced the progression of preexisting papillomas. The ability of benzoyl peroxide to enhance the progression of benign tumors to cancer should be considered when determining the human risk from exposure to this widely used chemical agent; in addition, biological assays specifically testing malignant progression may be essential and beneficial for determining an agent's carcinogenic risk.

Exposure to cutting oils and its relation to skin tumors and premalignant skin lesions on the hands and forearms

In a cohort study the incidence of skin tumors on the hands and forearms of 682 turners exposed to cutting oils was compared to the incidence of the general male population and of office workers. Among the 682 turners, five premalignant squamous cell tumors and eight keratoacanthomas were found between 1960 and 1980. Five of this total of 13 turners with primary skin tumors had another skin tumor as well. Among the 682 men there were four cases of scrotal cancer. Among the 375 office workers examined, no malignant or premalignant tumors or keratoacanthomas were found on the hands or forearms. No primary skin tumors were found among the turners after 1975, when the acid-refined mineral oils were replaced by solvent-refined oils containing a far lower concentration of polyaromatic hydrocarbons, which are probably the cancerogenic agent in the oils. The study shows a greatly increased risk of skin tumors on the hands and forearms of workers exposed to acid-refined mineral oils. Individual susceptibility also seems to be indicated.

Tumors of the anal region induced in mice painted with methylazoxymethanol acetate

The carcinogenicity of methylazoxymethanol acetate (MAM acetate) was examined in 91 BALB/c mice by painting it on the anal region. Carcinomas and adenomas of the perianal sebaceous gland were induced in 23 of 24 male (96%) and 16 of 30 female (53%) mice and keratoacanthoma developed in one of 24 male mice within 30 weeks after treatment with MAM acetate. Vascular tumors of the liver and fat issue of the abdominal cavity also developed in 16 of 24 male (67%) and 3 of 30 female (10%) mice treated with this drug. Microscopic adenocarcinomas were found in the rectal mucosa of 3 of 24 male mice adjacent to the anorectal junction. The sex difference in the incidence of tumors is briefly discussed.

Chemical carcinogenesis by the two-stage protocol in the skin Mastomys natalensis (Muridae) using topical initiation with 7,12-dimethylbenz(a)anthracene and topical promotion with 12-0-tetradecanoylphorbol-13-acetate

The long-term (34 weeks) topical administration of 7,12-dimethylbenz(a)anthracene (DMBA) to the skin of male and female Mastomys induced a broad spectrum of benign and malignant tumors in all animals treated. In a two-stage carcinogenesis experiment with topical initiation with DMBA and topical promotion with TPA, 50% of the animals developed both benign and malignant skin tumors. In general, benign tumors occurred between weeks 15 and 25, whereas malignant tumors were seen 40 weeks after initiation. In contrast to the situation in Mus musculus, the benign tumors consisted mainly of keratoacanthomas instead of fibroepitheliomas. In the non-initiated, TPA-treated, control group four benign and four malignant tumors were seen, whereas animals of the DMBA-initiated, acetone-treated control group were free of tumors. The promotion of virus transformed cells with TPA is discussed.

DMBA-induced tumors and their prevention by aromatic retinoid (Ro 10-9359)

Both auricles of 21 domestic rabbits were painted with dimethylbenzanthracene (DMBA). Eleven animals of this group were additionally fed aromatic retinoid (AR) by an esophageal tube. Two control animals were not treated at all. Eight or 9 weeks after the beginning of the study six of the seven remaining animals, which had only been painted with DMBA, developed a total of 25 keratoacanthoma-like tumors (KA). On the other hand, none of the seven animals left, which were painted with DMBA and fed AR showed any tumor by this time. The systemic effect of AR was studied in biopsies from the snout and the back. The epidermis of the snout showed 'mucous mataplasia' by histochemical and electron-microscopic criteria, whereas the epidermis of the back was not significantly altered. The production of intra- and extracellular lamellated material indicated an additional effect of AR on epidermal lipid metabolism. The effect of AR in the prevention of DMBA-induced tumors was characterized by 'mucoid cytolysis' and karyolysis.

Skin carcinogenesis as a model system: observations on species, strain and tissue sensitivity to 7,12-dimethylbenz(a)anthracene with or without promotion from croton oil

The pattern of development of tumours was studied in several mice strains, rabbits and pigs. Repeated carcinogen applications caused the appearance of numerous papillomas, keratoacanthomas and squamous cell carcinomas in Swiss, A, ASW/SN Balb/c and C57B1 mice, New Zealand and outbred laboratory rabbits. AKR mice were only little sensitive and Hormel mini pigs unresponsive. Initiation with 7,12-dimethylbenz(a)-anthracene and promotion with croton oil produced in Swiss, A, Balb/c and C3H mice as well as New Zealand rabbits a large number of squamous papillomas. Pigmented or adnexal tumours were not observed, and only a few dermal fibromas and fibrosarcomas.

Characteristics of neoplastic progression and tumor behavior in skin carcinogenesis by different methods: an experimental study

Characteristics of chemically induced skin tumor formation by different methods were studied in 600 Swiss mice. A large dose of 9,10-dimethylbenz(a)anthracene (DMBA) alone or followed by 12-0-tetradecanoyl-phorbol-13-acetate(tpa) and a small dose of DMBA followed by TPA or DMBA repeatedly induced papillomas in 80--90% of the animals. Of these 44--65% regressed and 11--16% became malignant. Keratoacanthomas, observed mainly in repeated DMBA treated animals, were seen to arise de novo in 1--12% of the animals, or from papillomas, 3--12%, they became malignant in 4--9% of the animals. Squamous cell carcinomas were formed de novo in 1--8% of the animals or from papillomas or keratoacanthomas in 10--14% of the animals. Duration of experiment and degree of malignancy related to size of tumor and level of invasion. It is concluded that tumor formation is a stepwise process, with the different types of treatment affecting different aspects of tumor formation to a varying degree.

Bioassay of complex mixtures derived from fossil fuels

The conversion or processing of shale, coal, or petroleum involves elevated temperatures and altered pressures, and under these conditions polynuclear aromatic hydrocarbons are likely to form. Certain compounds of this type exhibit carcinogenic activity for a variety of organ sites in experimental animals and epidemiological evidence strongly implicates their role as carcinogens in man. It is then not unexpected that many liquid fractions derived from shale and coal are carcinogenic when subjected to bioassay. Benzo(a)pyrene, [B(a)P], is frequently considered to be an indicator substance. It is clear that when a small quantity of B(a)P is present in a fraction, the fraction will exhibit carcinogenic activity in a bioassay (mouse skin). However, it does not follow that the lack of detectable B(a)P insures that the fraction will be noncarcinogenic. Several fractions have been analyzed for their content of B(a)P and then subjected to bioassay. A method for testing complex mixtures for their carcinogenic potential is described. The carcinogenic potency of these fractions are compared to petroleum fractions.

Non-immunological regression of dimethylbenz(A) anthracene-induced experimental keratoacanthomas in the rabbit

In 9 rabbits, with a total of 17 experimental keratoacanthomas, a search has been made for immune-mediated mechanisms which could possibly be involved in the spontaneous regression of these tumours. Immunofluorescence studies did not reveal significant staining patterns. With skin tests, using autologous extracts prepared in three different ways, no delayed cutaneous hypersensitivity reactions were observed.