Nonsurgical Treatments for Nonmelanoma Skin Cancer

A Comprehensive Review of Various Therapeutic Strategies for the Management of Skin Cancer

Skin cancer (SC) poses a global threat to the healthcare system and is expected to increase significantly over the next two decades if not diagnosed at an early stage. Early diagnosis is crucial for successful treatment, as the disease becomes more challenging to cure as it progresses. However, identifying new drugs, achieving clinical success, and overcoming drug resistance remain significant challenges. To overcome these obstacles and provide effective treatment, it is crucial to understand the causes of skin cancer, how cells grow and divide, factors that affect cell growth, and how drug resistance occurs. In this review, we have explained various therapeutic approaches for SC treatment via ligands, targeted photosensitizers, natural and synthetic drugs for the treatment of SC, an epigenetic approach for management of melanoma, photodynamic therapy, and targeted therapy for BRAF-mutated melanoma. This article also provides a detailed summary of the various natural drugs that are effective in managing melanoma and reducing the occurrence of skin cancer at early stages and focuses on the current status and future prospects of various therapies available for the management of skin cancer.

Combined Carbon Dioxide Laser with Photodynamic Therapy for Nodular Basal Cell Carcinoma Monitored by Reflectance Confocal Microscopy

Introduction: Basal cell carcinoma (BCC) represents around 80% of all malignant skin cancers worldwide, constituting a substantial burden on healthcare systems. Due to excellent clearance rates (around 95%), surgery is the current gold-standard treatment. However, surgery is not always possible or preferred by patients. Numerous non-surgical therapies, sometimes combined, have been associated with promising tumor free survival rates (80-90%) in non-melanoma skin cancers (NMSCs). Most research has enrolled superficial basal cell carcinomas (sBCCs), with limited recent studies also involving low-risk nodular BCCs (nBCCs). Given lower efficacy rates compared to surgery, close monitoring during the follow-up period is essential for patients treated with non-surgical therapies. Monitoring with dermoscopy is constrained by low sensitivity rates. Reflectance confocal microscopy (RCM) is more sensitive in monitoring non-surgically treated NMSCs. Case presentation: A 41-year-old woman with a single nBCC relapse following photodynamic therapy (PDT) located on the dorsum of the nose presented to our center. Given the aesthetically sensitive location of the lesion and the patient's preference for a non-surgical approach, a combined treatment of CO2 laser and PDT was prescribed. A superpulsed CO2 laser (power: 0.5-3 W, frequency: 10 Hz, spot size 2 mm) with two PDT sessions (2 weeks apart) were conducted. At 6 weeks follow-up, monitoring performed with RCM revealed a reduction but not eradication of basaloid tumor islands. Another 2 sessions of PDT were recommended. At 3, 12 and 30 months of follow-up, the nasal dorsum area of the previous nBBC lesion was noted to be slightly hypopigmented (observed clinically), with a mild erythematous background (observed by dermoscopy). RCM evaluation confirmed the absence of RCM BCC criteria. The cosmetic outcome was very much improved. Conclusions: Combined CO2 laser and PDT for the treatment of a localized nBCC on the dorsum of the nose of a 41-year-old proved to offer tumor free survival at 30-month follow-up, as monitored with RCM. RCM is useful for the evaluation of non-surgical therapies as it has comparably higher sensitivity than dermoscopy and is especially useful in cases of suspected late recurrence. Further studies are needed to validate ongoing tumor free survival following this combined nonsurgical approach in the treatment of nBCC.

Histopathological Pattern of Head and Neck Recurrent BCC After Previous Cryotherapy

Surgical resection is the gold standard treatment for basal cell carcinomas, although there is literature supporting cryotherapy for low-risk cases. Our aim was to compare the histopathological aspects of recurrent postcryotherapy head and neck cutaneous BCC with de novo tumors, using a case-control study. 51 Recurrent postcryotherapy cases were selected between January 2017 and December 2021 and compared to 132 controls filtered from a consecutive series of de novo head and neck cutaneous BCC operated between January and December 2021. Aggressive variants, multifocality, invasion beyond adipose tissue and higher Clark levels were associated with recurrent cases on multivariate analysis. Previous cryotherapy treatment may have contributed to an increased risk of more aggressive recurrent disease and caution using this treatment modality is advised.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12070-023-03919-7.

Non-Surgical Therapeutic Strategies for Non-Melanoma Skin Cancers

OPINION STATEMENT

Non-melanoma skin cancer (NMSC) is a globally prevalent skin disease, with basal cell carcinoma and squamous cell carcinoma accounting for 99% of NMSC cases. While surgical excision is the most common approach, numerous non-surgical therapies have rapidly advanced in recent years. In cases of low-risk NMSC, alongside surgical excision, priority should be given to physical therapy and photodynamic therapy. Physical therapy modalities, exemplified by electrodessication and curettage, emerge as safe and efficacious alternatives. In juxtaposition, photodynamic therapy, albeit relatively more costly, assumes preference for patients exhibiting heightened cosmetic concerns owing to the scarring risks inherent to physical therapy and surgical excision. Notably, the combination of curettage and photodynamic therapy has exhibited remarkable efficacy in the treatment of nodular basal cell carcinoma. Additionally, for elderly patients who may be intolerant to stimulation, modified photodynamic therapy offers an almost painless option. When surgery is unavoidable, photodynamic therapy can be a valuable adjunct, allowing for a more conservative surgical approach, either before or after the procedure. Radiotherapy holds a prominent role in comprehensive treatment strategies, especially for patients ineligible for surgical intervention or those with lesions precluding further surgical measures. In cases of NMSC exhibiting perineural invasion or lymphovascular involvement, adjunctive radiotherapy is advised; however, potential adverse effects necessitate careful consideration. For advanced NMSC cases where surgery and physical therapy fall short, immunotherapy provide viable solutions. Systemic therapy employing Hedgehog pathway inhibitors can be considered for patients with distant metastatic basal cell carcinoma, despite its low incidence, or individuals with locally advanced lesions who are not surgical candidates, or those encountering recurrences after resection and radiotherapy. However, close monitoring of disease progression and adverse reactions is crucial. In this evolving landscape of NMSC treatment, personalized and multidisciplinary approaches are key, ensuring optimal outcomes while prioritizing patient safety and satisfaction.

Cryosurgery for Basal Cell Skin Cancer of the Head: 15 Years of Experience

The clinical relevance of head and neck (H&N) tumors is related to the potential disfiguration of anatomical structures (by the tumor or surgical intervention), defining patients' individual features and emotional expression, loss or restraint of vital structures functions, and untoward socio-economic sequelae. This study is aimed to improve clinical outcomes of cryosurgery in patients with H&N basal cell skin cancer by refining the indications for cryosurgical treatment. In this study, cryosurgery was used in 234 patients with different stages of cutaneous basal cell carcinoma (BCC) of the head, including 101 patients with T1 tumors, 86-with T2, 5-T3, and 42 patients with tumors relapsing after failure of preceding various treatment modalities. Post-cryosurgery recurrence rate in patients with stage I BCC was 2.7%, with stage II tumors-5.6% and 34.9%-in patients with recurred tumors. Re-recurrence after cryoablation of recurrent tumors correlated with the tumor baseline size. The best aesthetic and long-term clinical results were documented in patients with lesions <1 cm in size with clear boundaries. Thus, cryosurgery is the method of choice for the majority of stage I basal cell carcinomas of the head. For patients with advanced and recurrent skin cancer, cryosurgery is relevant in rare cases selected according to refined indications.

Topical Treatments for Basal Cell Carcinoma and Actinic Keratosis in the United States

Skin cancer is an overarching label used to classify a variety of cutaneous malignancies. Surgical excision procedures are the commonly used treatments for these lesions; however, the choice to perform operative intervention may be influenced by other factors. Established research and literature suggest that topical treatments limit the need for surgical intervention and its commonly associated adverse effects, including infection and scarring. In addition, the growing indications for the usage of topical therapies in BCC treatment, as well as their increased availability and therapeutic options, allow for their greater applicability in the dermatology clinic. Certain topical therapies have been highlighted in research, especially those targeting basal cell carcinoma (BCC) and actinic keratosis (AK). There is also a clear correlation between cost and treatment outcomes, considering BCC's ever-growing prevalence and the proportion of excised lesions being reported as malignant. This review will discuss BCC and AK lesion criteria that result in the most successful outcomes using topical treatments, then highlight the various topical treatment options, and finally address their clinical significance moving forward.

Imiquimod as Local Immunotherapy in the Management of Premalignant Cutaneous Conditions and Skin Cancer

Cutaneous cancers are, by far, the most common malignant neoplasms of the human being. Due to the great array of clinical conditions, their worldwide increasing incidence and the steady ageing of the population, non-invasive treatments modalities that show a good clinical response, a proper benefit-risk ratio and cosmetic results are becoming increasingly important in the clinical setting. Imiquimod is a topically applied immunomodulator which is often used in the management of several premalignant and malignant cutaneous disorders. This article is a review of the current literature on its mechanism of action, pharmacokinetics, and therapeutical effects.

Nanomaterials for Skin Cancer Photoimmunotherapy

Skin cancer is one of the most common types of cancer, and its incidence continues to increase. It is divided into two main categories, melanoma and non-melanoma. Treatments include surgery, radiation therapy, and chemotherapy. The relatively high mortality in melanoma and the existing recurrence rates, both for melanoma and non-melanoma, create the need for studying and developing new approaches for skin cancer management. Recent studies have focused on immunotherapy, photodynamic therapy, photothermal therapy, and photoimmunotherapy. Photoimmunotherapy has gained much attention due to its excellent potential outcomes. It combines the advantages of photodynamic and/or photothermal therapy with a systemic immune response, making it ideal for metastatic cancer. This review critically discusses different new nanomaterials' properties and mechanisms of action for skin cancer photoimmunotherapy and the main results obtained in the field.

The Role of Radiation Therapy in the Treatment of Non-Melanoma Skin Cancer

Non-melanoma skin cancer (NMSC) is the most common malignancy in the United States. While surgery is considered as the main treatment modality for both cutaneous basal cell carcinoma (cBCC) and cutaneous squamous cell carcinoma (cSCC), radiotherapy plays an important role in the treatment of NMSC, both in the adjuvant setting for cases considered high-risk for recurrence, and in the definitive setting, when surgery is not feasible or desired by the patient. The last years have seen the emergence of immunotherapy treatment for cases of advanced cSCC in the palliative, and possibly neoadjuvant settings, making the treatment paradigm more complex. In this review, we attempt to describe the different radiation modalities available for the treatment of NMSC, the indications for adjuvant post-operative treatment with radiotherapy for cSCC, the role of radiotherapy in elective neck treatment, and the efficacy, safety, and toxicity profile of this treatment in these different settings. Furthermore, we aim to describe the efficacy of radiotherapy combined with immunotherapy as a promising horizon for treating advanced cSCC. We also aim to describe the ongoing clinical studies that attempt to examine future directions for the role of radiation treatment in NMSC.

Inhibition of the TRIM24 bromodomain reactivates latent HIV-1

Expression of the HIV-1 genome by RNA Polymerase II is regulated at multiple steps, as are most cellular genes, including recruitment of general transcription factors and control of transcriptional elongation from the core promoter. We recently discovered that tripartite motif protein TRIM24 is recruited to the HIV-1 Long Terminal Repeat (LTR) by interaction with TFII-I and causes transcriptional elongation by stimulating association of PTEF-b/ CDK9. Because TRIM24 is required for stimulation of transcription from the HIV-1 LTR, we were surprised to find that IACS-9571, a specific inhibitor of the TRIM24 C-terminal bromodomain, induces HIV-1 provirus expression in otherwise untreated cells. IACS-9571 reactivates HIV-1 in T cell lines bearing multiple different provirus models of HIV-1 latency. Additionally, treatment with this TRIM24 bromodomain inhibitor encourages productive HIV-1 expression in newly infected cells and inhibits formation of immediate latent transcriptionally repressed provirus. IACS-9571 synergizes with PMA, ionomycin, TNF-α and PEP005 to activate HIV-1 expression. Furthermore, co-treatment of CD4 + T cells from individuals with HIV-1 on antiretroviral therapy (ART) with PEP005 and IACS-9571 caused robust provirus expression. Notably, IACS-9571 did not cause global activation of T cells; rather, it inhibited induction of IL2 and CD69 expression in human PBMCs and Jurkat T cells treated with PEP005 or PMA. These observations indicate the TRIM24 bromodomain inhibitor IACS-9571 represents a novel HIV-1 latency reversing agent (LRA), and unlike other compounds with this activity, causes partial suppression of T cell activation while inducing expression of latent provirus.

Repurposing of ingenol mebutate for treating human colorectal cancer by targeting S100 calcium-binding protein A4 (S100A4)

Colorectal cancer (CRC) is the world's second most common cause of cancer-related death. Novel treatments are still urgently needed. S100 calcium-binding protein A4 (S100A4) was demonstrated to be an anticancer therapeutic target. Herein, we found that higher S100A4 expression was associated with a poorer prognosis in publicly available cohorts and a Taiwanese CRC patient cohort. To identify repurposed S100A4 inhibitors, we mined the Connectivity Map (CMap) database for clinical drugs mimicking the S100A4-knockdown gene signature. Ingenol mebutate, derived from the sap of the plant Euphorbia peplus, is approved as a topical treatment for actinic keratosis. The CMap analysis predicted ingenol mebutate as a potent S100A4 inhibitor. Indeed, both messenger RNA and protein levels of S100A4 were attenuated by ingenol mebutate in human CRC cells. In addition, CRC cells with higher S100A4 expressions and/or the wild-type p53 gene were more sensitive to ingenol mebutate, and their migration and invasion were inhibited by ingenol mebutate. Therefore, our results suggest the repurposing of ingenol mebutate for treating CRC by targeting S100A4.

Non-Melanoma Skin Cancer Clearance after Medical Treatment Detected with Noninvasive Skin Imaging: A Systematic Review and Meta-Analysis

Simple Summary

Non-melanoma skin cancers (NMSC) represent about one-third of all malignancies. While surgery is the current gold standard treatment, many nonsurgical approaches are available for selected cases. Currently, there are no studies concerning the overall impact of dermoscopy, optical coherence tomography (OCT) and reflectance confocal microscopy (RCM) for NMSC treatment monitoring. Therefore, we aim to review the current literature and provide an updated summary of noninvasive skin imaging in NMSC medical treatment management and the diagnostic accuracy of the most advanced technologies.

Abstract

Background/Objectives: Non-melanoma skin cancer (NMSC) treated with nonsurgical therapies can be monitored with noninvasive skin imaging. The precision of dermoscopy, reflectance confocal microscopy (RCM) and optical coherence tomography (OCT) in detecting clearance is unclear. We aim to report the proportion of persisting tumors identified with noninvasive technologies available in the literature. Methods: A systematic literature search was conducted on the PubMed and Cochrane Public Library Databases for articles published prior to November 2021. Statistical analyses were conducted with MedCalc 14.8.1 software. Results: A total of eight studies (352 lesions) reporting noninvasive imaging for NMSC clearance following nonsurgical treatment were included. Most (n = 7) reported basal cell carcinoma (BCC), and one study reported squamous cell carcinoma (SCC) clearance. A meta-analysis of the BCC clearance revealed that the summary effect for RCM was higher, as compared to the other techniques. Interestingly, the sensitivity and specificity for OCT were 86.4% (95% CI: 65.1–97.1) and 100% (95% CI: 94.8–100.0), respectively, whilst, for RCM, they reached 100% (95%CI: 86.8–100) and 72.5% (95% CI: 64.4–79.7), respectively. Conclusions: Routine clinical examination and dermoscopy underperform when employed for NMSC clearance monitoring, although they represent the first approach to the patient. OCT and RCM seem to improve the detection of persistent BCC after medical treatment.

Antibody-Antineoplastic Conjugates in Gynecological Malignancies: Current Status and Future Perspectives

In the last decade, antibody-drug conjugates (ADCs), normally formed by a humanized antibody and a small drug via a chemical cleavable or non-cleavable linker, have emerged as a potential treatment strategy in cancer disease. They allow to get a selective delivery of the chemotherapeutic agents at the tumor level, and, consequently, to improve the antitumor efficacy and, especially to decrease chemotherapy-related toxicity. Currently, nine antibody-drug conjugate-based formulations have been already approved and more than 80 are under clinical trials for the treatment of several tumors, especially breast cancer, lymphomas, and multiple myeloma. To date, no ADCs have been approved for the treatment of gynecological formulations, but many formulations have been developed and have reached the clinical stage, especially for the treatment of ovarian cancer, an aggressive disease with a low five-year survival rate. This manuscript analyzes the ADCs formulations that are under clinical research in the treatment of gynecological carcinomas, specifically ovarian, endometrial, and cervical tumors.

Nobiletin-loaded composite penetration enhancer vesicles restore the normal miRNA expression and the chief defence antioxidant levels in skin cancer

Skin cancer is one of the most dangerous diseases, leading to massive losses and high death rates worldwide. Topical delivery of nutraceuticals is considered a suitable approach for efficient and safe treatment of skin cancer. Nobiletin; a flavone occurring in citrus fruits has been reported to inhibit proliferation of carcinogenesis since 1990s, is a promising candidate in this regard. Nobiletin was loaded in various vesicular systems to improve its cytotoxicity against skin cancer. Vesicles were prepared using the thin film hydration method, and characterized for particle size, zeta potential, entrapment efficiency, TEM, ex-vivo skin deposition and physical stability. Nobiletin-loaded composite penetration enhancer vesicles (PEVs) and composite transfersomes exhibited particle size 126.70 ± 11.80 nm, 110.10 ± 0.90 nm, zeta potential + 6.10 ± 0.40 mV, + 9.80 ± 2.60 mV, entrapment efficiency 93.50% ± 3.60, 95.60% ± 1.50 and total skin deposition 95.30% ± 3.40, 100.00% ± 2.80, respectively. These formulations were selected for cytotoxicity study on epidermoid carcinoma cell line (A431). Nobiletin-loaded composite PEVs displayed the lowest IC50 value, thus was selected for the in vivo study, where it restored skin condition in DMBA induced skin carcinogenesis mice, as delineated by histological and immuno-histochemical analysis, biochemical assessment of skin oxidative stress biomarkers, in addition to miRNA21 and miRNA29A. The outcomes confirmed that nobiletin- loaded composite PEVs is an efficient delivery system combating skin cancer.

Post-burn scar malignancy: 5-year management review and experience

The study spotlights a severe uncommon post‐burn complication, Marjolin's ulcer, in upper Egypt plastic and wound care centres. This problem is mainly related to inadequate medical care and awareness. No community or race is immune. The underlying malignant transformation mechanism remains unclear. The study aims, according to our experience, to review the prognostic factors through the management protocol of Marjolin's ulcers. This prospective study was conducted in the Aswan University Plastic & Burn surgery department in South Egypt between 2013 and 2020 and investigated 226 patients with chronic post‐burn ulceration. Nineteen cases were proved to have Marjolin's ulcer, and the other cases that had been excluded from being malignant went for reconstruction with split‐thickness skin graft with/without flap after adequate ulcer debridement. The surgical, oncologic, radiologic indications, and prognostic factors were reviewed according to our management outcome—the assessment with follow‐up period extended over 5 years. Histopathology of ulcers ranged among mild, moderate, and poorly differentiated squamous cell carcinoma. One scalp ulcer case showed basosquamous pathology. Most cases presented at age above 50, but no age was immune. The mean latent period was 29 years on average. The lesions' sites varied in their anatomic location where they involved the upper extremity, the scalp, and the lower extremity that had a predilection. Although surgical excision is the primary management line for tumour ablation, other factors may change the management course. During the follow‐up period, neoplasm recurrence in the form of lymph node enlargement and/or locoregional metastasis was detected in eight cases. Within 1 year after the intervention, six recurrent cases died, and two were saved. In addition to the case study, this paper reviewed the literature and provided our team a good experience in light of the NCCN protocol for non‐melanotic cutaneous carcinoma, although we suffered limited medical resources. It is concluded that early accurate diagnosis, low‐grade malignancy, and well‐planned individualised surgery with adjuvant radiotherapy were the best prognostic factors. The close follow‐up for an early sign of disease recurrence is paramount.

Successful treatment of a giant keratoacanthoma-like squamous cell carcinoma in the eyebrow using surgery combined with photodynamic therapy: A case report

Keratoacanthoma (KA)-like squamous cell carcinoma (SCC) is inclined to be diagnosed as KA due to its resemblance to KA in appearance. A giant facial KA-like SCC has aggressive growth and malignant metastasis, and seriously affects health and aesthetics. Prompt and appropriate treatment is extremely crucial and is a great challenge. Herein, we report a case of surgery combined with 5-aminolevulinic acid photodynamic therapy (ALA-PDT) in the successful management of a giant KA-like SCC in the left eyebrow of an elderly woman, providing reference for more efficient disposal of such cases in clinic.

New Developments in the Management of Cutaneous Squamous Cell Carcinoma

LEARNING OBJECTIVES

After studying this article, the participant should be able to: 1. List important prognostic features that affect cutaneous squamous cell carcinoma risk. 2. Summarize the changes to the AJCC Cancer Staging Manual, Eighth Edition, staging system for cutaneous squamous cell carcinoma. 3. Evaluate the draining nodal basin with appropriate imaging modalities. 4. Recommend adjuvant radiation therapy in the correct clinical setting for high-risk tumors. 5. Recognize the currently available treatments for advanced cutaneous squamous cell carcinoma.

SUMMARY

This continuing medical education article reviews the features, management, and prognosis of cutaneous squamous cell carcinoma with an emphasis on high-risk squamous cell carcinoma and data from the past 3 years. This review will discuss the primary tumor management, high-risk features of a squamous cell carcinoma, changes to the American Joint Committee on Cancer staging system, and the utility of sentinel lymph node biopsy, and critically review the evidence regarding adjuvant therapy.

Simultaneous Targeting Tumor Cells and Cancer-Associated Fibroblasts with a Paclitaxel-Hyaluronan Bioconjugate: In Vitro Evaluation in Non-Melanoma Skin Cancer

BACKGROUND

Cancer-associated fibroblasts (CAFs) facilitate many aspects of cancer development by providing a structural framework rich in bioactive compounds. There are emerging studies proposing a combination of conventional anti-cancer therapies directed against neoplastic cells to molecules targeting tumor microenvironments.

METHODS

The study evaluated the pharmacological properties of the anti-tumor agent paclitaxel conjugated to hyaluronic acid (HA) regarding non-melanoma skin cancer (NMSC) and the surrounding fibroblasts. This molecule, named Oncofid-P20 (Onco-P20), preferentially targets cells expressing high levels of CD44, the natural ligand of HA.

RESULTS

Consistent with paclitaxel's mechanism of action involving interference with the breakdown of microtubules during cell division, highly sensitive carcinoma cells rapidly underwent apoptotic cell death. Interestingly, less sensitive cells, such as dermal fibroblasts, resisted the Onco-P20 treatment and experienced a prolonged growth arrest characterized by morphological change and significant modification of the gene expression profile. Onco-P20-treated fibroblasts exhibited reduced growth factor production, downmodulation of the Wnt signaling pathway, and the acquisition of a marked pro-inflammatory profile. Independently of direct exposure to taxol, in the presence of Onco-P20-treated fibroblasts or in their conditioned medium, carcinoma cells had a reduced proliferation rate. Similar to NHF, fibroblasts isolated from skin cancer lesions or from adjacent tissue acquired anti-neoplastic activity under Onco-P20 treatment.

CONCLUSION

Collectively, our data demonstrate that Onco-P20, exerting both a direct and an NHF-mediated indirect effect on carcinoma cells, is a candidate for an innovative therapy alternative to surgery for the treatment of NMSC.

Treatment of Non-melanoma Skin Cancers in the Absence of Mohs Micrographic Surgery

Non-melanoma skin cancers are the most common malignancies globally. Although non-melanoma skin cancers exhibit low metastatic potential, they can be locally destructive, necessitating complex excisions and reconstructions. Mohs micrographic surgery is the gold-standard treatment for high-risk non-melanoma skin cancers in patients who are appropriate surgical candidates. Despite its efficacy, Mohs micrographic surgery is not readily available in most geographic regions, necessitating that plastic surgeons be well-versed in alternative treatment modalities for non-melanoma skin cancer. Herein, we will discuss the management of non-melanoma skin cancers in settings where Mohs micrographic surgery is not readily available.

Improving the Efficacy of EGFR Inhibitors by Topical Treatment of Cutaneous Squamous Cell Carcinoma with miR-634 Ointment

For cutaneous squamous cell carcinoma (cSCC), topical treatment is an essential option for patients who are not candidates for, or who refuse, surgery. Epidermal growth factor receptor (EGFR) plays a key role in the development of cSCC, but EGFR tyrosine kinase inhibitors (TKIs), such as gefitinib, have shown only partial clinical benefit in this disease. Thus, there is an unmet need to develop novel strategies for improving the efficacy of TKIs in cSCC. We previously demonstrated that the tumor-suppressive microRNA (miRNA) miR-634 functions as a negative modulator of the cytoprotective cancer cell survival processes and is a useful anticancer therapeutic agent. In the present study, we found that topical application of an ointment containing miR-634 inhibited in vivo tumor growth without toxicity in a cSCC xenograft mouse model and a 7,12-dimethylbenz[a]anthracene (DMBA)/12-O-tetradecanoylphorbol-13-acetate (TPA)-induced papilloma mouse model. Functional validation revealed that miR-634 overexpression reduced glutaminolysis by directly targeting ASCT2, a glutamine transporter. Furthermore, overexpression of miR-634 synergistically enhanced TKI-induced cytotoxicity by triggering severe energetic stress in vitro and in vivo. Thus, we propose that topical treatment with miR-634 ointment is a useful strategy for improving for EGFR TKI-based therapy for cSCC.