Autologous human preclinical modeling of melanoma interpatient clinical responses to immunotherapeutics

BACKGROUND

Despite recent advances in immunotherapy, a substantial population of late-stage melanoma patients still fail to achieve sustained clinical benefit. Lack of translational preclinical models continues to be a major challenge in the field of immunotherapy; thus, more optimized translational models could strongly influence clinical trial development. To address this unmet need, we designed a preclinical model reflecting the heterogeneity in melanoma patients' clinical responses that can be used to evaluate novel immunotherapies and synergistic combinatorial treatment strategies. Using our all-autologous humanized melanoma mouse model, we examined the efficacy of a novel engineered interleukin 2 (IL-2)-based cytokine variant immunotherapy.

METHODS

To study immune responses and antitumor efficacy for human melanoma tumors, we developed an all-autologous humanized melanoma mouse model using clinically annotated, matched patient tumor cells and peripheral blood mononuclear cells (PBMCs). After inoculating immunodeficient NSG mice with patient tumors and an adoptive cell transfer of autologous PBMCs, mice were treated with anti-PD-1, a novel investigational engineered IL-2-based cytokine (nemvaleukin), or recombinant human IL-2 (rhIL-2). The pharmacodynamic effects and antitumor efficacy of these treatments were then evaluated. We used tumor cells and autologous PBMCs from patients with varying immunotherapy responses to both model the diversity of immunotherapy efficacy observed in the clinical setting and to recapitulate the heterogeneous nature of melanoma.

RESULTS

Our model exhibited long-term survival of engrafted human PBMCs without developing graft-versus-host disease. Administration of an anti-PD-1 or nemvaleukin elicited antitumor responses in our model that were patient-specific and were found to parallel clinical responsiveness to checkpoint inhibitors. An evaluation of nemvaleukin-treated mice demonstrated increased tumor-infiltrating CD4+ and CD8+ T cells, preferential expansion of non-regulatory T cell subsets in the spleen, and significant delays in tumor growth compared with vehicle-treated controls or mice treated with rhIL-2.

CONCLUSIONS

Our model reproduces differential effects of immunotherapy in melanoma patients, capturing the inherent heterogeneity in clinical responses. Taken together, these data demonstrate our model's translatability for novel immunotherapies in melanoma patients. The data are also supportive for the continued clinical investigation of nemvaleukin as a novel immunotherapeutic for the treatment of melanoma.

Abstract PO-029: USP14 is a potential target to improve the efficacy of radiotherapy in combination with immune-checkpoint inhibitors in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) represents ~85% of lung cancer cases and has a 5-year survival rate of ~23%. Thus, research aimed at determining more effective treatment strategies is critical. Immune checkpoint inhibitors (ICis), e.g. anti-PD-L1 antibodies, have transformed cancer treatment in recent years. Clinical trial studies have indicated that radiotherapy enhances the curative effect of ICis. However, most patients do not respond to immune-radiotherapy combinations. While best known to induce DNA double strand break (DSB)-mediated cytotoxicity, ionizing radiation (IR) induces an increase of cytosolic DNA and activates the cyclic GMP-AMP synthase/stimulator of interferon genes (cGAS/STING) signaling pathway that leads to the type 1 interferon (IFN) response, essential to achieve anti-tumor immunity in combination with ICis. Homologous recombination (HR) DNA repair deficiency is an important determinant of radiation response that can also increase the immune recognition of cancers by increasing the number of non-synonymous mutations, as well as by increasing the cGAS/STING-mediated type1 IFN response. We have shown an important role for ubiquitin specific protease (USP14) in regulating DNA repair (1, 2,3). Here, we identify a novel role of USP14 in regulating HR and the cGAS/STING pathway in response to IR in NSCLC. USP14 is a proteasomal deubiquitinase that we show to have a prominent role in NSCLC. Knockdown of USP14 (shUSP14) or its pharmacological inhibition (IU1 or VLX1570) led to: (i) radio-sensitization, as shown by reduced clonogenic survival in NSCLC cell lines, and delayed growth of NSCLC tumor xenografts in nude mice; increased (ii) HR-deficiency; (iii) chromosomal aberrations and micronuclei formation; as well as (iv) cGAS puncta in response to IR. Further, USP14 interacts with and deubiquitinates cGAS in IR-treated NSCLC cells. USP14-mediated deubiquitination of cGAS has been shown to inhibit cGAS protein turn-over and increase the levels of cGAS in response to virus infection. Unexpectedly, however, in response to IR shUSP14 NSCLC cells have significantly higher cytoplasmic cGAS puncta and type 1 IFN response. Overall, these findings identify USP14 as a potential target to enhance sensitization to immune-radiotherapy by both regulation of HR and direct regulation of cGAS ubiquitination, leading to type 1 IFN response. Understanding the mechanisms that regulate DSB repair and cGAS/STING pathways holds potential for developing strategies to enhance the effectiveness of immune-radiotherapy combinations in NSCLC.

References 1. Sharma et al, (2108) USP14 regulates DNA damage repair by targeting RNF168-dependent ubiquitination. Autophagy, 14: 1976-90. 2. Sharma et al. USP14 is a deubiquitinase for Ku70 and critical determinant of non-homologous end joining repair in autophagy- and PTEN-deficient cells. Nucleic Acids Res. 48: 736-47. 3. Sharma, Almasan (2020). USP14 regulates DNA damage response and is a target for radiosensitization in non-small cell lung cancer. Int J Mol Sci. 21: 6383.

Citation Format: Arishya Sharma, Yvonne Parker, Claudia Marcela Diaz-Montero, Daniel Lindner, Alexandru Almasan. USP14 is a potential target to improve the efficacy of radiotherapy in combination with immune-checkpoint inhibitors in non-small cell lung cancer [abstract]. In: Proceedings of the AACR Virtual Special Conference on Radiation Science and Medicine; 2021 Mar 2-3. Philadelphia (PA): AACR; Clin Cancer Res 2021;27(8_Suppl):Abstract nr PO-029.

Evaluation of T cell infiltration in matched biopsy and nephrectomy samples in renal cell carcinoma

T cell infiltration in tumors has been investigated as a biomarker of response to checkpoint inhibitors. Neo-adjuvant studies in renal cell carcinoma (RCC) may provide a unique opportunity to compare T cell infiltration in a pretreatment renal mass biopsy to a posttreatment nephrectomy specimen, and thus evaluate the effects of immune checkpoint inhibitors. However, there are no data regarding the association of T cell infiltration in matched biopsy and nephrectomy samples without intervening treatment. Understanding this association will inform investigation of this potential biomarker in future studies.Matched biopsy and nephrectomy samples (without intervening systemic therapy) were identified from patients with nonmetastatic RCC. Selected tissue sections from biopsy and nephrectomy samples were reviewed and marked for intratumoral lymphocytes by a pathologist. Immunohistochemistry (IHC) was utilized to stain for T cell markers (CD3, CD4, and CD8). Intratumoral staining was then quantified in the tissue sections as counts per total tumor area surveyed. Spearman correlation (r) was used to measure associations.Thirty matched pairs were investigated. The median interval between biopsy and nephrectomy was 2.8 (0.2-87.7) months. Clear cell was the most common histology (29/30; 97%). There was a statistically significant positive correlation between the frequency of CD3 and CD8 T cells between matched biopsy and nephrectomy samples (r = 0.39; P = .036 and r = 0.38; P = .041, respectively).The frequencies of CD8+ T cells in matched biopsy and nephrectomy samples in RCC in the absence of intervening treatment have been characterized and show a positive correlation between matched biopsy and nephrectomy samples.

Challenges faced when identifying patients for combination immunotherapy

In 1996, Jim Allison demonstrated that blocking the immune regulatory molecule CTLA-4 with anit-CTLA4 antibody led to enhance tumor responses in mice. It would take an additional 15 years for human studies to confirm the potency and clinical efficacy of anti-CTLA4, ultimately leading to US FDA approval of the first checkpoint inhibitor, ipilimumab. Now with a plethora of immune-modulating agents demonstrating single agent safety and benefit across many tumor types, investigation on the optimal combination of immune-based therapies has begun in earnest. While there are many challenges, a central one is how to select which combination for which patient is the best. Here we review the current approaches that a practitioner can use to achieve this therapeutic goal.

Phase 2 study of neoadjuvant treatment with NOV-002 in combination with doxorubicin and cyclophosphamide followed by docetaxel in patients with HER-2 negative clinical stage II-IIIc breast cancer

NOV-002 (a formulation of disodium glutathione disulfide) modulates signaling pathways involved in tumor cell proliferation and metastasis and enhances anti-tumor immune responsiveness in tumor models. The addition of NOV-002 to chemotherapy has been shown to increase anti-tumor efficacy in animal models and some early phase oncology trials. We evaluated the clinical effects of NOV-002 in primary breast cancer, whether adding NOV-002 to standard preoperative chemotherapy increased pathologic complete response rates (pCR) at surgery, and determined whether NOV-002 mitigated hematologic toxicities of chemotherapy and whether levels of myeloid derived suppressor cells (MDSC) were predictive of response. Forty-one women with newly diagnosed stages II-IIIc HER-2 negative breast cancer received doxorubicin-cyclophosphamide followed by docetaxel (AC → T) every 3 weeks and concurrent daily NOV-002 injections. The trial was powered to detect a doubling of pCR rate from 16 to 32% with NOV-002 plus AC → T (α = 0.05, β = 80%). Weekly complete blood counts were obtained as well as circulating MDSC levels on day 1 of each cycle were quantified. Of 39 patients with 40 evaluable tumors, 15 achieved a pCR (38%), meeting the primary endpoint of the trial. Concurrent NOV-002 resulted in pCR rates for AC → T chemotherapy higher than previously reported. Patients with lower levels of circulating MDSCs at baseline and on the last cycle of chemotherapy had significantly higher probability of a pCR (P = 0.02). Further evaluation of NOV-002 in a randomized study is warranted.