Efficacy of recombinant alpha-interferon 2a and 13-cis-retinoic acid in the treatment of squamous cell carcinoma

Oral Isotretinoin and Its Uses in Dermatology: A Review

In 1982, the Food and Drug Administration (FDA) of the United States of America approved isotretinoin (13-cis-retinoic acid), a retinoid derivative of vitamin A, to treat severe recalcitrant acne vulgaris. Apart from its prescribed use for severe acne, evidence suggests that isotretinoin is commonly used off-label to treat mild-to-moderate acne, inflammatory skin conditions, genodermatoses, skin cancer, and other skin disorders. This is due to its anti-inflammatory, immunomodulatory, and antineoplastic properties. Some "off-label" use is successful, while others are ineffective. Therefore, this information is essential to clinicians for deciding on the appropriate use of isotretinoin. In this article, we aim to review the most updated evidence-based data about the use of oral isotretinoin in dermatology.

Systemic acitretin in the management of periocular squamous cell carcinoma

We report a case of periocular squamous cell carcinoma invading the anterior orbit that significantly reduced in size and regressed from invasive to in situ following treatment with oral acitretin, a second-generation retinoid. The residual in situ disease was then successfully treated with cryotherapy and the patient remains in remission 12 months following cessation of systemic acitretin.

Oral isotretinoin for the treatment of dermatologic conditions other than acne: a systematic review and discussion of future directions

While isotretinoin has been the gold-standard of therapy for severe acne since its approval in 1982, its anti-inflammatory properties makes it a potentially applicable and versatile therapy for a wide variety of dermatologic conditions yet to be explored. This systematic review comprehensively recounts the success of oral isotretinoin in non-acne cutaneous diseases and provide insight into future directions of isotretinoin utility. A systematic literature review was performed using PubMed. Search terms included "isotretinoin" OR "accutane" AND "skin" OR "dermatology" OR "hair" OR "nails" OR "rosacea" OR "psoriasis" OR "pityriasis rubra pilaris" OR "condyloma acuminata" OR "granuloma annulare" OR "darier's disease" OR "non-melanoma skin cancer" OR "frontal fibrosing alopecia" OR "cutaneous lupus erythematosus" OR "hidradenitis suppurativa" OR "photodamaged skin" OR "skin aging" OR "wart" OR "flat warts" OR "plane warts" OR "lichen planus" OR "dissecting cellulitis" OR "folliculitis decalvans" OR "sebaceous hyperplasia" OR "cutaneous t-cell lymphoma" OR "mycosis fungoides." A total of 169 studies discuss the use of oral isotretinoin for 16 non-acne dermatologic conditions, the most common being non-melanoma skin cancers (0.2-8.2 mg/kg/day), cutaneous T-cell lymphomas (0.5-2 mg/kg/day), and rosacea (0.22-1 mg/kg/day). Inflammatory conditions such as rosacea, granuloma annulare, and hidradenitis suppurativa benefit from lower oral isotretinoin dosage of 0.3-1 mg/kg/day, whereas, hyperkeratotic diseases such as psoriasis and pityriasis rubra pilaris, consistently respond better to higher dosages of up to 2-4 mg/kg/day for lesion clearance. Recurrence of disease following discontinuation of isotretinoin have been reported for rosacea, psoriasis, granuloma annulare, Darier's disease, dissecting cellulitis, and non-melanoma skin cancers. Disease exacerbation was reported in some patients with hidradenitis suppurativa. Off-label isotretinoin is an effective treatment choice for dermatological conditions beyond acne. Further prospective, randomized human trials are needed to clarify when and how to prescribe off-label isotretinoin for maximum efficacy and safety.

Do tetracyclines and erythromycin exert anti-acne effects by inhibition of P450-mediated degradation of retinoic acid?

For decades, retinoic acid (RA) is known as the most potent therapeutic option in the therapy of acne and altered homeostasis of endogenous retinoids has been discussed in the context of acne pathogenesis. Besides retinoids, antibiotics such as tetracyclines or erythromycin are well established in acne pharmacotherapy. Accumulating evidence points towards common molecular pathways being targeted by both RA and anti-acne antibiotics; however, a precise 'common denominator' connecting these chemically diverse anti-acne agents has not yet been identified. Interestingly, tetracyclines are associated with the occurrence of pseudotumor cerebri, a rare neurological side effect otherwise associated with retinoid intoxication or RA exposure. This association at the clinical level suggests an interaction between tetracyclines and endogenous RA signalling. As erythromycin does not cross the blood brain barrier, CNS side effects are not to be expected, yet not precluding a possible local interaction of erythromycin with endogenous RA metabolism in the skin. We hypothesize tetracyclines and erythromycin to locally inhibit endogenous RA metabolism in the skin and thus mimic therapeutic action of RA. This readily testable hypothesis suggests inhibition of endogenous RA metabolism and amplification of endogenous RA signalling as a mechanism underlying the biochemical actions of antibiotics in acne therapy. Elucidation of such interactions may ultimately enhance our understanding of acne therapy and pathogenesis and may yield a sound, scientific basis for hypothesis-driven development of novel therapeutic compounds.

Phase 2 trial of paclitaxel, 13-cis retinoic acid, and interferon alfa-2b in the treatment of advanced stage or recurrent cervical cancer

OBJECTIVE

Overexpression of bcl-2 is a mechanism of drug resistance in cervical cancer. Agents that down-regulate bcl-2 may decrease tumor cell threshold and sensitize tumor cells to chemotherapy. The objective of this multi-institutional phase 2 trial was to evaluate the efficacy and toxicity of paclitaxel and bcl-2 modulators (13-cis retinoic acid and interferon alfa-2b) in patients with advanced-stage or recurrent cervical cancer.

MATERIALS AND METHODS

Patients had biopsy-proven metastatic, first relapse, or persistent cervical cancer with no prior chemotherapy except for chemosensitizing agents. The treatment consisted of oral 13-cis retinoic acid, 1 mg/kg, and subcutaneous interferon alfa-2b, 6 mU/m, days 1 to 4, and intravenous paclitaxel, 175 mg/m, day 4 until disease progression or adverse events prohibited treatment. The primary endpoint was overall response rate.

RESULTS

Thirty-three patients were enrolled between March 2001 and June 2009. Thirty-one patients were eligible for evaluation of treatment response. Twenty-seven patients (82%) received prior concurrent chemoradiation or radiotherapy alone before study enrollment. The overall response rate was 30% (6 complete responses and 4 partial responses). Furthermore, 7 patients (21%) had stable disease. Grade 3 or 4 adverse events included neutropenia (n =16 [48%]), febrile neutropenia (n = 1 [3%]), and anemia (n = 1 [3%]). There were no treatment-related deaths. The median progression-free survival was 3.4 months (95% confidence interval, 2.0-7.4 months), and overall survival was 11.2 months (95% confidence interval, 7.5-26.2 months). Of 6 patients with complete responses, 5 patients survived more than 2 years.

CONCLUSIONS

Combination therapy with paclitaxel, 13-cis retinoic acid, and interferon alfa-2b is feasible and safe in treating patients with advanced and recurrent cervical cancer.

Off-label uses of biologics in dermatology: Interferon and intravenous immunoglobulin (Part 1 of 2)

The introduction of a number of biologic therapies into the market has revolutionized the practice of dermatology. These therapies include interferons, intravenous immunoglobulin, infliximab, adalimumab, etanercept, efalizumab, alefacept, and rituximab. Most dermatologists are familiar with the Food and Drug Administration-approved indications of these medications. However, numerous off-label uses have evolved. As part 1 of a 2-part series, this article will review the literature regarding the off-label uses of the interferons and intravenous immunoglobulin in dermatology.

Prospective, Randomized, Multicenter, Double-Blind Placebo-Controlled Trial Comparing Adjuvant Interferon Alfa and Isotretinoin With Interferon Alfa Alone in Stage IIA and IIB Melanoma: European Cooperative Adjuvant Melanoma Treatment Study Group

Purpose

The combination of interferon alfa (IFNα) and isotretinoin has shown a direct antiproliferative effect on human melanoma cell lines, but it remained unclear whether this combination is more effective than IFNα alone in patients with metastatic melanoma. We evaluated safety and efficacy of IFNα and isotretinoin compared with IFNα alone as adjuvant treatment in patients with primary malignant melanoma stage IIA and IIB.

Patients and Methods

In a prospective, randomized, double-blind, placebo-controlled trial, 407 melanoma patients in stage IIA (301 patients) and IIB (106 patients) were randomly assigned to either IFNα and isotretinoin (isotretinoin group; 206 patients) or IFNα and placebo (placebo group; 201 patients) after excision of the primary tumor. IFNα was administered three times a week at a dose of 3 million units subcutaneously for 24 months. Isotretinoin at a dose of 20 mg for patients ≤ 73 kg, 30 mg for patients greater than 73 kg, or placebo daily for 24 months.

Results

A scheduled interim analysis revealed no significant differences in survival rates, with the isotretinoin group and the placebo group showing 5-year disease-free survival rates of 55% (95% CI, 46% to 65%) and 67% (95% CI, 59% to 75%), respectively, and overall 5-year survival rates of 76% (95% CI, 67% to 84%) and 81% (95% CI, 74% to 88%), respectively. The trial was stopped for futility.

Conclusion

The addition of isotretinoin to an adjuvant treatment of low-dose IFNα in patients with stage IIA and IIB melanoma had no significant effect on disease-free or overall survival and is therefore not recommended.

Non-acne dermatologic indications for systemic isotretinoin

Systemic isotretinoin has been used to treat severe acne vulgaris for 20 years. However, isotretinoin also represents a potentially useful choice of drugs in many dermatologic diseases other than acne vulgaris. Diseases such as psoriasis, pityriasis rubra pilaris, condylomata acuminata, skin cancers, rosacea, hidradenitis suppurativa, granuloma annulare, lupus erythematosus and lichen planus have been shown to respond to the immunomodulatory, anti-inflammatory and antitumor activities of the drug. Isotretinoin also helps prevent skin cancers such as basal cell carcinoma or squamous cell carcinoma. A combination of systemic isotretinoin and interferon-alpha-2a may provide a more potent effect than isotretinoin alone in the prevention and treatment of skin cancers.Systemic isotretinoin may be considered as an alternative drug in some dermatologic diseases unresponsive to conventional treatment modalities. However, randomized clinical trials aimed at determining the role of systemic isotretinoin therapy in dermatologic diseases other than acne vulgaris are required.

The GRIMs: a new interface between cell death regulation and interferon/retinoid induced growth suppression

Cytokines and vitamins play a central role in controlling neoplastic cell growth. The interferon (IFN) family of cytokines regulates antiviral, anti-tumor, antimicrobial, differentiation, and immune responses in mammals. Significant advances have been made with respect to IFN-induced signal transduction pathways and antiviral responses. However, the IFN-induced anti-tumor actions are poorly defined. Although IFNs themselves inhibit tumor growth, combination of IFNs with retinoids (a class of Vitamin A related compounds) strongly potentiates the IFN-regulated anti-tumor action in a number of cell types. To define the molecular mechanisms involved in IFN/retinoid (RA)-induced apoptosis we have employed a genetic approach and identified several critical genes. In this review, I provide the current picture of IFN- RA- and IFN/RA-regulated growth suppressive pathways. In particular, I focus on a novel set of genes, the genes-associated with retinoid-interferon induced mortality (GRIM). GRIMs may be novel types of tumor suppressors, useful as biological response markers and potentially novel targets for drug development.

Interferon trials in small cell lung cancer at one institution: a comparison of results obtained before and after initiation of systematic treatment trials using IFN-alpha in combination with other modalities

Chemotherapy became the primary treatment for small cell lung cancer (SCLC) in the early 1970s. The standard drug combinations were first vincristine, adriamycin, and cyclophosphamide (VAC) and then, from the early 1980s, etoposide-platinum combinations. Despite a good initial objective response, however, patients usually suffer a rapid relapse. Treatment development has, therefore, focused on ways to overcome drug resistance, and on the addition of cytokines to the chemotherapeutic arsenal. Interferon (IFN) was one of the first cytokines found to have anticancer effects, and it was introduced into the combined modality regimens used to treat SCLC in the early 1980s in an attempt to overcome the problem of early relapse. The role of IFN was investigated with the aim of establishing how best to combine it with other treatments for SCLC. In this paper, we review the impact of IFN on the outcome for 714 SCLC patients who were treated in randomized IFN trials at one institution over a period of 20 years and IFN trials conducted at other institutions during the same period. The parameters we used at our institution to measure outcome tended to improve during the period when patients were being treated in our three randomized IFN trials, compared with the period when patients received only standard treatment in a nonclinical trial setting. However, the differences were not statistically significant. During this period, IFN was used as maintenance therapy, concomitantly with chemotherapy, and combined with other treatment modalities. Our experience is that IFN-alpha is most effective when administered as low-dose maintenance treatment. Other IFN trials published during the same period were small and heterogeneous. Results were inconsistent and added little new information, although it has been shown that high pretreatment levels of serum vascular endothelial growth factor (VEGF) predict a poor response to treatment and consequently a poor outcome. The recently confirmed antiangiogenic properties of IFN deserve to be investigated in studies of maintenance treatment, in combination with other biologic agents. Patient should be selected according to criteria based on pretreatment assessment of biologic markers, such as VEGF and basic fibroblast growth factor (bFGF). Our studies, all at one institution, pioneered the biologic treatment of solid tumors and developed a solid basis of knowledge for future studies of biologic agents in cancer treatment.

Interferon-alpha and 13-cis-retinoic acid as maintenance therapy after high-dose combination chemotherapy with growth factor support for small cell lung cancer--a feasibility study

This randomized phase II multi-center study was designed to determine the time to progression, duration of response and the feasibility of an intensified maintenance regime consisting of a combination of interferon (IFN)-alpha and retinoic acid after high-dose combination chemotherapy and radiotherapy in patients with small cell lung cancer. The patients received four courses of combination chemotherapy consisting of ifosfamide, carboplatin and etoposide, with higher doses of ifosfamide and carboplatin given in the first course, with routine growth factor support. Responding patients were then randomly assigned to one of three maintenance therapy arms. All patients with limited disease (LD) were given thoracic radiotherapy before maintenance therapy and those who had also achieved a complete response (CR) or minimal residual disease (MRD) received prophylactic cranial irradiation. In Arm 1 patients received IFN-alpha-2a, 6 MIU s.c. TIW for 4 weeks, followed by 3 MIU s.c. TIW, and 13-cis-retinoic acid 1 mg/kg/day p.o. BID daily. In Arm 2 patients received trophosphamide 100-150 mg/day p.o. BID. No maintenance treatment was given in Arm 3, the control group. Maintenance therapy was continued for 1 year. Eighty-five patients were treated according to the protocol. Twenty-one patients achieved CR, four achieved MRD and forty-two achieved partial responses to chemotherapy and radiotherapy. Sixty patients (71%) were randomly assigned for maintenance treatment. Median survival was 17.1 months in the IFN-alpha-retinoic acid arm, 12.4 months in the trophosphamide arm and 13.5 months in the control arm. One-year survival rates were 82, 56 and 55%, respectively. Duration of response was 6.5, 5.5 and 4.7 months, respectively. Time to progression was 8.6, 8.0 and 6.8 months, respectively The differences were not statistically significant. The IFN-alpha-retinoic acid maintenance treatment was well tolerated. Patients who received IFN-alpha-retinoid maintenance therapy lived longer after the onset of progressive disease. The treatment regime was effective, feasible and well tolerated.

Retinoids in lung cancer chemoprevention and treatment

In this review, we aim to synthesize the emerging picture of retinoids in lung cancer through a summary of ongoing investigations in biology, chemoprevention and therapy settings, in an attempt to clarify the possible role of these agents in such a disease. Early work in head and neck cancer has evidenced the capability of retinoids to interrupt field carcinogenesis by reversing premalignant lesions and decreasing the incidence of second primary tumors (SPTs). At this time, the completed randomized trials in lung cancer have failed to demonstrate an evident chemopreventive effect of the tested agents on different study end points, although both a marginally significant benefit of retinol palmitate in time-to-development rates for smoke-related SPTs and a potential preventive effect of retinol supplementation against mesothelioma in selected populations of asbestos-exposed workers have been recently reported. Concerning the role of retinoids in lung cancer treatment, a moderate activity of 13-cis-retinoic acid (13cRA) or all-transretinoic acid (ATRA) as single agents has been reported in small series of advanced, mostly pretreated lung cancer patients. More encouraging findings derive from combination studies, in which retinoids, especially ATRA, are added to either alpha-interferon or chemotherapy and radiotherapy. Major recent advances have been made towards the understanding of retinoids mechanisms of action; at this regard, the role of RAR-beta basal or treatment-induced levels seems to be of particular interest as intermediate end point and/or independent prognostic factor, besides their known importance in lung carcinogenesis. Future research for chemopreventive and therapeutic programs with retinoids in lung cancer should be focused on the investigation of new generation compounds with a specificity for individual retinoid nuclear receptors. Such selective molecules may have a greater activity against lung cancer, with a more favourable toxicity profile, as recently suggested by our preliminary data on Ro 41-5253.

Radiation sensitivity of human squamous cell carcinoma cells in vitro is modulated by all-trans and 13-cis-retinoic acid in combination with interferon-alpha

PURPOSE

Retinoids and interferon-alpha (IFN-alpha) have been shown to exert antiproliferative and radiosensitizing effects. The present study was designed to determine differential effects of retinoids in combination with IFN-alpha on radiation toxicity of 5 human squamous cell carcinoma (SCC) cell lines.

METHODS AND MATERIALS

Using clonogenic assays, the effects of all-trans (ATRA), 13-cis-retinoic acid (13cRA), and IFN-alpha on radiation toxicity were analyzed. Basal mRNA expression of the cytoplasmic retinoic acid binding protein, CRABP I, was determined in retinoid-sensitive and -insensitive cell lines by reverse transcriptase/polymerase chain reaction (RT-PCR).

RESULTS

Treatment with ATRA, 13cRA, or IFN-alpha resulted in a cell line-specific inhibition of clonogenic survival. A comparison of retinoid-sensitive and insensitive cells revealed that retinoid sensitivity seems to be dependent on the basal expression level of CRABP I. ATRA, 13cRA, and IFN-alpha alone or in combination altered radiation sensitivity by affecting predominantly the alpha-component of the linear-quadratic dose-response curve. Likewise, depending upon the treatment condition the surviving fraction at 2 Gy (SF2) was decreased cell line-specifically. Combined treatment with ATRA or 13cRA and IFN-alpha markedly enhanced radiation cytotoxicity.

CONCLUSION

These in vitro data indicate that the combined treatment with retinoids, IFN-alpha, and ionizing radiation could be beneficial for patients presenting with SCC.

Phase II clinical trial of 13-cis-retinoic acid and interferon-alpha-2a in patients with advanced esophageal carcinoma

BACKGROUND

Interferon in combination with 5-fluorouracil has been shown to be active in squamous cell carcinoma (SCC) and adenocarcinoma (AC) of the esophagus. 13-cis-retinoic acid (CRA) has chemopreventive activity in SCC of the head and neck, and, in combination with interferon, has antitumor activity in SCC of the skin and cervix.

METHODS

The activity and toxicity of CRA and interferon-alpha-2a (IFN) in patients with advanced esophageal carcinoma was evaluated in a Phase II single institution trial. Patients had unresectable or metastatic AC or SCC of the esophagus. One prior chemotherapy regimen was allowed. IFN was given by daily subcutaneous injection at a dose of 3 million U and CRA was taken orally at a dose of 1 mg/kg/day in 2 divided doses. Treatment was given in cycles of 4 weeks and continued until documented disease progression.

RESULTS

Of the 19 patients entered, 15 were evaluable for response and toxicity. One patient was evaluable for response only and one patient was evaluable for toxicity only. Evaluable patients were predominantly male (15 patients), and had AC (13 patients). All had AJCC Stage IV disease and 12 were pretreated. Patients completed an average of two cycles of therapy (range, one to six cycles) prior to progression of disease. National Cancer Institute Common Toxicity Criteria Grade 3/4 toxicity was notable for nausea (25%) and fatigue (31%). No major objective responses were recorded. Eleven patients with AC and 3 patients with SCC had rapid progression of disease. One patient with AC was found to have a minor response for 22 weeks and 1 patient with AC had stable disease for 45 weeks.

CONCLUSIONS

This regimen had no significant activity in patients with advanced AC of the esophagus. Further evaluation of IFN plus CRA, using this dose and schedule, is not recommended. In comparison with prior trials of this therapy, a surprising amount of severe nausea and fatigue was observed in this trial.

Chemoprevention with interferon alfa and 13-cis retinoic acid in the adjunctive treatment of head and neck cancer

BACKGROUND

Retinoids have been increasingly used since the mid-1960s for the treatment of leukoplakia and dysplasia of the head and neck. Studies of their use in the treatment of carcinomas of the head and neck, usually in combination with interferons, have also been published in recent years.

METHODS

30 patients (25 men, five women) with UICC stage IV were given adjunctive treatment with a combination of 3 x 3 million IU of interferon alfa SC weekly and 0.5 mg/kg body weight of 13-cis retinoic acid PO daily for a maximum duration of 6 months. The therapeutic benefits and side effects are reported here.

RESULTS

Therapy was completed as scheduled in 16 out of 30 patients. Reasons for stopping treatment: progressive disease (ten patients), side effects (four patients). 18 patients were tumor-free following treatment. 16 patients displayed a complete response one year after completion of adjunctive treatment. Retinoic-associated side effects observed included xerostomia (90%), dysphagia (67%), weight loss (50%), flush (50%) and cachexia (7%). Interferon-associated side effects included pyrexia and moderate hematological changes.

CONCLUSION

Adjunctive combination treatment with interferon alfa and 13-cis retinoic acid appears to be beneficial to patients with head and neck cancer. The side effects are moderate.

A 2-week pretreatment with 13-cis-retinoic acid + interferon-alpha-2a prior to definitive radiation improves tumor tissue oxygenation in cervical cancers

BACKGROUND

We have evaluated the tumor tissue pO2 in cervical cancers in patients treated with 13-cis-retinoic acid and interferon-alpha-2a prior to and during radiotherapy.

PATIENTS AND METHODS

From June 1995 through April 1997, 22 patients with squamous cell carcinoma FIGO IIB/III of the cervix who were scheduled for definitive radiotherapy with curative intent received additional treatment with 13-cis-retinoic acid (cRA, isotretinoin) plus interferon-alpha-2a (IFN-alpha-2a) as part of a phase-II protocol. cRA/IFN-alpha-2a started 14 days prior to radiotherapy (1 mg per kilogramme body weight cRA orally daily plus 6 x 10(6) IU IFN-alpha-2a subcutaneously daily). After this induction period, standard radiotherapy was administered (external irradiation with 50.4 Gy in 28 fractions of 1.8 Gy plus HDR-brachytherapy). During radiotherapy, cRA/IFN-alpha-2a treatment was continued with 50% of the daily doses. Tumor tissue pO2-measurements were performed prior to and after the cRA/IFN-induction period as well as at 20 Gy and at the end of radiotherapy with an Eppendorf-pO2-histograph.

RESULTS

In 11 out of the 22 patients, pO2-measurements were performed prior to the cRA/IFN-induction therapy. The median pO2 of these untreated tumors was 17.7 +/- 16.3 mm Hg. The relative frequency of hypoxic readings with pO2-values below 5 mm Hg ranged from 0% to 60.6% (mean 24.3 +/- 21.0%). After the 2-week induction period with cRA/IFN, the median pO2 had increased from 17.7 +/- 16.3 mm Hg to 27.6 +/- 19.1 mm Hg (not significant). In all 5 patients with hypoxic tumors prior to cRA/IFN (median pO2 of 10 mm Hg or less), the median pO2 was above 20 mm Hg after the 2-week cRA/IFN-induction. In this subgroup of hypoxic tumors, the median pO2 increased from 6.3 +/- 2.7 mm Hg to 27.0 +/- 5.6 mm Hg (p = 0.004, t-test for paired samples). The frequency of hypoxic readings (pO2-values < 5 mm Hg) decreased from 44.7 +/- 17.1% to 2.0 +/- 2.5% (p = 0.012, t-test for paired samples). There was, however, no obvious volume reduction after 14 weeks of cRA/IFN on clinical examination. A complete clinical remission of the local tumor was observed in 19/22 patients after radiotherapy and additional cRA/IFN-alpha-2a-treatment. In primarily hypoxic tumors (with a median pO2 below 10 mm Hg prior to treatment), 4/5 achieved complete remission.

CONCLUSIONS

Pretreatment with cRA/IFN improves oxygenation of primarily hypoxic cervical cancers. The mechanisms of action remain unclear and further investigation of the combination regimen is recommended.

Interferons in dermatology. Present-day standard

Since the first clinical trials in the early 1980s with recombinant interferon, it was possible to show for a variety of indications that cytokines, especially interferons, at certain doses and at respective intervals, when applied in combination with other pharmaceutical compounds open new powerful therapeutic possibilities. Worldwide, recombinant interferon is licensed, especially in dermato-oncology, for the indication of HIV-associated Kaposi's sarcoma, cutaneous T-cell lymphoma, and recently for adjuvant therapy of high-risk malignant melanoma. Recombinant interferon is at present not licensed for dermatologic indication (septic granulomatosis). At the end of our century the indication spectrum for interferons as monotherapy and as combination therapy will undoubtedly be extended. Larger and controlled studies will prove the importance of interferons in dermato-oncology as well as in inflammatory and infectious dermatoses. The combination of interferons with standard therapies will surely be of the utmost importance in dermatotherapy.

Antiproliferative and synergistic effect of interferon alpha-2a, retinoids and their association in established human cancer cell lines

The effect of 13-cis-retinoic acid (cRA) and all-trans-retinoic acid (tRA) used alone or in combination with interferon alpha-2a (alpha-IFN 2a) was tested on three established human cell lines: KB (epidermoid carcinoma of the oral cavity), SCC-25 (tongue squamous cell carcinoma) and MCF-7 (mammary carcinoma). Both retinoids significantly decreased cell proliferation (growth curves) and colony forming efficiency (CFE) in all cell lines, in a dose-dependent way (at a concentration ranging from 10(-5) to 10(-9) M) and differing from line to line, following the pattern: MCF-7 > SCC-25 > KB. Retinoids at any concentration (already at 10(-7) M) combined with alpha-IFN 2a (ranging from 100 to 500 IU/ml) were more effective in inhibiting cell proliferation than each of the two compounds alone. This was particularly evident with SCC-25 cells. Concerning MCF-7 cells, on the contrary, the effects produced by the association suggested a possible additive more than synergistic amplification of growth inhibition.